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106 Cards in this Set
- Front
- Back
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What is the important connection between quantum mechanics and the arrangement of the atoms in the periodic table?
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It describes the electronic structure of atoms, which correlates with the arrangement of the periodic table.
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Core electrons?
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Electrons not in outermost shell of an atom. Close to nucleus, results in strong attraction to nucleus. Strong attraction to nucleus makes them chemically inert. Shield valance electrons from nucleus.
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Valance electrons?
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Electrons in the highest value of n. Used in bondings between atoms (chemically reactive).
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Shielding?
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When core electrons act as though they are a part of nucleus, which in turn lowers nuclear charge between nucleus and valance shell elections
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Why is effective nuclear charge not an exact method to determine actual effective nuclear charge of elections in atoms?
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It assumes that core electrons are always closer to nucleus than valance electrons but valance shell electrons can penetrate closer to the nucleus than core electrons for some types of orbitals (making valance shell electrons more strongly attracted to nucleus than what the effective nuclear charge would state).
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Equation for approximating effective nuclear charge?
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Z (effective nuclear charge)= Z(# of protons)-S(orbital constant, which is close to # of core electrons in atom)
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Why are valance shell electrons not good at screening other valance shell electrons from nucleus?
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For valance shell electrons to effective screen other valance shell electrons from nucleus, they have to be close to the nucleus than other valance shell electrons.
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Why can electrons in “s” orbitals screen electrons in “p” orbitals, but electrons in “p” orbitals cannot screen electrons from “s” orbitals?
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Electrons in “s” orbitals can screen electrons in “p” orbitals because of characteristics of “s” orbitals. Electrons in “s” orbitals are sometimes closer to nucleus than electrons in “p” orbital. Since they are closer to nucleus than electrons from “p” orbitals, they can screen electrons in “p” orbitals from nucleus (but this effect, alas, is negligible).
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What is equation for effective nuclear charge?
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Z(eff)=Z(where z= #protons-#core electrons)-S(where S is some “screening” constant which depends on specific orbitals)
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As you go down a group/column in periodic table, how does Z(eff) change?
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It increases.
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Why does Z(eff) increase as you go down a column in periodic table?
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All atoms have same valance shell configuration, but as you go down a column, the principal quantum number increases. An increase in principal quantum number means that there is an increase in the size of the electron core and larger electron cores are less able to screen valance shell electrons than smaller electron cores.
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As you go across a row in periodic table, how does Z(eff) change?
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It increases
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How is the atomic radius of ionic compounds determined?
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Determined from crystal structure of ionic compounds. Then average of interatomic distances from multiple compounds is taken.
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Bond length?
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The distance between atoms in covalently bound compound, averaged over many compounds.
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Nonbonding length?
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The closest distance that two neutral atoms or molecules can be together when they collide in the gas phase or when they are in crystal structures.
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Why are bond lengths between covalent bonds smaller than atomic radii of atoms?
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When two atoms covalently bond, they physically merge, share same electrons, and move closer to each other in a volume of space than what their atomic radii would have previously allowed for.
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Bonding radius?
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Half of the distance between the two nuclei of atoms when they are bonded together.
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As you go down a column in PT, how does atomic radii change?
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It increases.
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Why does atomic radii increase as you go down a column in PT?
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Principal quantum number increases (n). Some, having more core electrons near nucleus pushes valance shell electrons farther away from nucleus, thus making atomic radii larger.
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As you go horizontally across a row in PT, how does atomic radii change?
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It decreases.
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Why does atomic radii decrease as you go horizontally across a row in PT?
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Z(eff) increases. More protons in nucleus pulls electrons closer to nucleus, making atomic radius smaller.
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Do cations have a smaller or larger atomic radii compared to neutral atoms?
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They have smaller atomic radii.
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Why do cations have smaller atomic radii than neutral atoms?
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Since cations lose an electron, they have fewer electron-electron repulsions, which allow electrons to be closer to nucleus. Thus making atomic radii smaller.
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Do anions have smaller or larger atomic radii than neutral atoms?
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They have larger atomic radii.
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Why do anions have larger atomic radii than neutral atoms?
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Anions have larger atomic radii because they have more electrons than neutral atoms. More electrons increase the electron-electron repulsions, which increase the size of atomic radii.
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Isoelectronic series?
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A group of atoms/ions with the same electronic structure/configuration. The trend is determined by Z(eff).
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Ionization energy?
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The amount of energy required to remove an electron from the atom in the gas phase.
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As you go down a group, what happens to the ionization energy?
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It decreases.
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Why does the ionization energy decrease as you go down a group?
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It decreases because as you go down a group, your valance shell electron is farther and farther away from the nucleus, so the valance shell electron is not as strongly attracted to the nucleus as core electrons. So, the farther away the valance shell electron is from the nucleus, the easier it is to remove a valance shell electron from an atom, thus the IE decreases.
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As you go across a period, what happens to the ionization energy?
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It increases.
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Why does the ionization energy increase as you go horizontally across a period in PT?
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It increases because the number of core electrons does not increase and the increasing number of valance shell electrons do not shield one another effectively, but the number of protons increases, so the valance shell electrons are more strongly attracted to the nucleus as you go horizontally across a period in PT. Since the valance shell electrons are more strongly attracted to the nucleus, they are harder to remove from the atom, and thus the IE increases.
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What is the trend about ionization energy when removing electrons from full orbitals?
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Since full orbitals are stable and the nucleus is happy and does not want to gain or lose more electrons, it is much harder to remove electrons from these stable and full orbitals. Thus, the IE is much higher when trying to remove electrons from full orbitals (e.g. s2, p6, d10, f14).
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Is it easier or harder to remove electrons from cations or neutral atoms?
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It would be harder to remove electrons from cations than from neutral atoms.
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Is it easier or harder to remove electrons from anions or neutral atoms?
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It is easier to remove electrons from anions than form neutral atoms.
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Why is it harder to remove electrons from cations than from neutral atoms?
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Because the electrons are more strongly attracted to nucleus and closer to nucleus as well.
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Why is it easier to remove electrons from anions than from neutral atoms?
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Because the electrons are less strongly attracted to nucleus and farther away from nucleus.
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What is ionization energy dependent upon?
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IE depends on the average distance that the electron is away from the nucleus and the Z(eff).
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What is so significant about the fact that it takes more IE to remove electrons from full orbitals than from other non-full orbitals?
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It is significant to note that it takes more IE to remove electrons from full orbitals because there are blimps in PT trends, where an atom can have a higher Z(eff) than another atom but a lower IE.
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What is the general trend for ionization energy for transition metals?
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It generally increases as you move across a period from left to right in transition metals (not a pretty trend though).
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What happens to IE when you move out of transition metals (i.e. when you move from “d” orbitals to “p” orbitals)?
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When you move out of transition metals (from “d” orbitals to “p” orbitals), you see a drop in the ionization energy.
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Why do you see a drop in IE when you move out of transition metals (from “d” orbitals to “p” orbitals)?
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Because there is only one valance shell electron is in the “p” orbital and the atom wants to lose that valance shell electron in an unfavorable orbital so that it can have full orbital (like a full “d” orbital).
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Electron affinity?
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The energy associated with the gain of an electron in the gas phase.
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Why is ionization energy always coupled with electron affinity?
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Because they are each ½ of a redox reaction (I.e. it takes ionization energy to remove electrons from one atom and electron affinity to stick those newly free electrons onto another atom, and so this process can only take place when each step is carried out, and thus IE and EA are coupled together).
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Why are group 2A atoms an exception to the trends in electron affinity in PT?
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Atoms in group 2A have a full orbital of electrons, so they do not want to gain more electrons, which is why it takes more energy to be put into the atom to add more electrons to it (e.g. Be and Mg have positive EA, and the rest of the atoms in Group 2A have EA very close to 0).
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Why are group 5A atoms an exception to the general trends in electron affinity in PT?
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Atoms in group 5A all have a stable degenerate “p” sub shell because their “p” sub shell is half full. So, because these atoms have a stable sub shell, they do not want to gain more electrons, which is why their EA is higher (closer to 0) than the EA of surrounding atoms (i.e. it takes more energy to make the atom accept an extra electron because that atoms does not want to accept an extra electron because it already has a stable orbital of electrons).
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Why are group 8A atoms an exception to the general trends in electron affinity in PT?
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Atoms in group 8A all have a full shell of electrons, and so they do not want to gain or lose any more electrons. Because they do not want to gain or lose any more electrons, their EA is higher (closer to 0), which means that it takes more energy to force Group 8A to accept an extra electron into their orbitals.
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What is the trend for the energy required for the second electron affinity?
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The second EA always requires energy (EA is positive) because it takes energy to put an extra electron onto an anion (because electron-electron repulsions want to repel any other addition of electrons).
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Why do Metals form cations?
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Because they have low ionization energies.
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Why do you not see Group 1A or Group 2A metals with charges of +3?
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Because it takes too much energy to remove an electron from their “p” orbitals, when they form a stable octet of valance electrons (like in the noble gas electron configuration).
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When would you see electrons in “p” orbitals being removed?
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Electrons in “p” orbitals are generally removed from atoms when the atoms are to the right of the transition metals.
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Why do redox reactions occur between metals and nonmetals?
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Redox reactions occur between metals and nonmetals because the metal is oxidized (loses electrons) due to low ionization energy and the nonmetal is reduced (gains electrons) due to really low EA (which is a good thing, remember).
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What is the main characteristic of metal oxides?
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Metal oxides are basic (H+ proton acceptor). Since metal oxides are basic, they can be neutralized in acid base reactions (forming salt compounds and water).
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What are the physical properties of metals?
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Physical properties of metals include: luster (shinny), malleable (able to be pounded into sheets), ductile (able to be pulled into wires), and good conductors of heat and electricity.
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Why are Group 6A atoms exceptions to the general trends in IE?
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Because they have 4 electrons in their “p” orbital, and so they want to lose that fourth electron to have 3 electrons in their degenerate sub shell (“p” orbital) because having 3 electrons in their “p” orbital is a much more stable arrangement of electrons than having 4 electrons in their “p” orbital.
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What are the general characteristics of nonmetals, in terms of IE and EA?
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Generally speaking, nonmetals have high IE and large negative EA, which is why they usually react by gaining electrons to achieve a noble gas configuration.
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What is the significance of oxides of nonmetals being acidic?
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Since oxides of nonmetals are acidic, they form acids (i.e. they are proton donors).
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What are the physical properties of nonmetals?
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Not lustrous (not shiny), color of nonmetals varies widely, not malleable, not ductile, poor conductors of electricity, poor conductors of heat.
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What are the characteristics of metalloids in terms of IE and EA, and their significance?
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Metalloids have high IE potentials, so they will not easily form cations and they have EA that are not negative enough to form anions (this relationship between IE and EA may be a reason why metalloids have characteristics that are between metals and nonmetals).
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What makes a metalloid have characteristics more or less like metals and nonmetals?
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Metalloids have properties of either metals or nonmetals, dependent on the compounds that metalloids form. For example, if a metalloid reacts with a metal, it will have characteristics that are more like the properties of metals.
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What are the characteristics of Group 1A Alkali Metals?
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Group 1A Alkali Metals are soft and have low densities because of the large size of their atoms. In addition, their valance shell electron configuration is ns1, which means that their IE is relatively small; making one electron is easily lost to form M+ ions with noble gas electron configuration (this characteristics makes them very reactive).
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How are Group 1A Alkali Metals found in nature?
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Group 1A Alkali Metals are found in nature as salts.
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What is the practical use for Na?
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Na is used in replacement reactions to produce other reactive metals.
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What are oxides?
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Oxides have chemical formula of O^2-.
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What are peroxides?
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Peroxides have chemical formula of O_2^-2
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What are superoxides?
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Superoxides have chemical formula of O_2^-1.
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What is hydride?
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H^1-
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Why are Alkali metals stored under oil?
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Alkali metals are stored under oil because they are so reactive with oxygen and water.
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What happens to the reactivity between Alkali metals and water as you go down the column of alkali metals?
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As you go down the column of Alkali metals, the reactivity with water increases.
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What are the characteristics of Group 2A Alkaline Earth Metals?
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Harder, more dense, and less reactive than Alkali Metals because of their decreased size and increased Z(eff) across period (it takes a lot of E to remove both electrons). Valance shell electron configuration is ns^2, so loss of 2 electrons makes them have a noble gas electron configuration. Found in nature as cations.
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Why is Ba different from all other Group 2A Alkaline Earth Metals?
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Ba reacts with oxygen to form peroxide while all other Group 2A Alkaline Earth Metals reactive with oxygen to form oxides.
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What is the product of group 2A alkaline earth metals reacting with water?
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When Group 2A Alkaline Earth Metals react with water they form oxides and hydroxides. And their reactivity with water increases as you go down the group.
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What happens when Alkaline Earth Metals react with hydrogen?
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When alkaline earth metals react with hydrogen, it forms hydride.
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What is H^+ in aqueous solutions?
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In aqueous solutions, H^+ really means H_3O^+.
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Ionic bond?
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An electrostatic attraction between positive and negative ions resulting from electron transfer.
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Covalent bond?
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Sharing of electrons between two atoms.
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Which electrons are involved in chemical bonding and where are they found in an atom?
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Only valance shell electrons are involved in chemical bonding. These electrons are in the outermost occupied shell of an atom.
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Why are valance shell electrons the only electrons that are involved in chemical bonding between atoms?
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Valance shell electrons are the only electrons involved in chemical bonding because they are the electrons that are most easily lost or gained to fill an octet (the core electrons are so close to the nucleus that to it takes too much energy to remove or add electrons to core shell of electrons).
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Octet rule?
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Atoms tend to gain, lose, or share electrons until they are surrounded by 8 valance electrons (i.e. until their “s” and “p” orbitals are filled up). There are many exceptions to octet rule.
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What is the resulting compound in ionic bonding?
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The resulting compound in ionic bonding is an array (lattice or crystal structure) of positive and negative ions pack so attractive forces between ions of opposite charges are maximized and repulsive forces between like charges are minimized.
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Lattice energy?
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A measure of the strength of attraction in the solid crystal lattice. Defined as the energy required to separate 1 mol of solid ionic compounds into its gaseous ions.
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Why do Group 1A metals only form cations of 1+ charge?
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It is more energetically favorable for group 1A metals to lose 1 electron (relatively low IE) and form a noble gas formation than to either lose more than 1 electron or to gain enough electrons to reach a noble gas configuration for their valance electrons.
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Why do Group 2A metals only form cations of 2+ charge?
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It is more energetically favorable for group 2A metals to lose 2 electrons (relatively low IE) and form a noble gas formation than to either lose more than 2 electrons or to gain enough electrons to reach a noble gas configuration for their valance electrons.
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Why do Group 3A metals only form cations of 3+ charge?
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It is more energetically favorable for group 3A metals to lose 3 electron (relatively low IE) and form a noble gas formation than to either lose more than 3 electrons or to gain enough electrons to reach a noble gas configuration for their valance electrons.
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Why do Group 7A nonmetals form anions of 1- charge?
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It is more energetically favorable for group 7A nonmetals to gain 1 additional electron to form a noble gas valance shell electron configuration rather than to gain more than 1 electron or to lose enough electrons to form a noble gas valance shell electrons.
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Why do Group 6A nonmetals form anions of 2- charge?
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It is more energetically favorable for group 6A nonmetals to gain 2 additional electrons to form a noble gas valance shell electron configuration rather than to gain more than 2 electrons or to lose enough electrons to form a noble gas valance shell electrons.
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Why do Group 5A nonmetals form anions of 3- charge?
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It is more energetically favorable for group 5A nonmetals to gain 3 additional electrons to form a noble gas valance shell electron configuration rather than to gain more than 3 electrons or to lose enough electrons to form a noble gas valance shell electrons.
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Why do Group 4A nonmetals form anions of 4- charge?
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It is more energetically favorable for group 4A nonmetals to gain 4 additional electrons to form a noble gas valance shell electron configuration rather than to gain more than 4 electrons or to lose enough electrons to form a noble gas valance shell electrons.
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Why are transition metals exceptions to the octet rule?
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Because they can hold more than 8 valance electrons in their “d” orbital.
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Why do transition metals form ions by losing valance shell electrons from their “s” orbitals before they lose valance shell electrons from their “d” orbitals?
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Because atoms lose electrons first from the sub shell having the largest value of “n.” Thus, since transition metals have “s” orbitals that have a larger value of “n” than their “d” orbitals, they lose valance shell electrons from their “s” orbitals before they lose electrons from their “d” orbitals. Then, they lose as many “d” electrons that are required for them to reach the charge of the ion that they want.
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Why do transition metals not form cations with charges greater than 3+?
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Losing more than 3 electrons requires so much energy that losing more than 3 electrons and forming cations with charges greater than 3+ becomes an unfavorable process.
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Why do ionic bonds generally form between metals and nonmetals?
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Because metals have low IE and nonmetals have high EA.
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What are the characteristics of ionic boning?
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Ionic bonds are very strong which results in very high melting points but the crystal structure leads to brittle solids that cleave along plans of atoms (like along the x or y-plane).
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What is a coordinate covalent bond?
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This is a covalent bond where both of the shared electrons between two atoms actually come from only one atom.
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What are ionic bond lengths?
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The sum of the ionic radii of the two ions (remember, this is the hard sphere model of atoms).
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What is the main characteristic of covalent bond lengths?
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These bond lengths are shorter than the sum of the atomic radii of the two atoms, which is a result of overlap or “merging” of the orbitals (a key feature of covalent bond lengths).
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What are ionic bonds a result of?
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Strong electrostatic attractions between oppositely charge ions.
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What are covalent bonds a result of?
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They are the result of electrostatic attraction between the 2 nuclei to the 2 electrons, which “spend” most of their time between the 2 nuclei (unlike ionic bonds where the two atoms do not “share” electrons because one atom gives an electron to another atom and forms a bond in the process due to strong electrostatic forces).
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What is the general trend with bond lengths and number of bonds?
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The higher number of bonds between two atoms, the shorter the bond lengths are (e.g. triple bond is shorter in length than a double bond and a double bond is shorter in length than a single bond).
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What is the general trend with bond strength and number of bonds?
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The higher number of bonds between two atoms, the stronger the bond are (e.g. triple bond is stronger than a double bond and a double bond stronger than a single bond).
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What is electronegativity?
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Electronegativity is the ability of an atom in a molecule to attract electrons to itself.
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What is electronegativity proportional to?
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Electronegativity is proportional to IE and EA. An atom with a very negative EA and high IE will both attract electrons from other atoms and resist having its electrons attracted away from it (and as a result will have a high electronegativity).
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What is the trend for electronegativity as you go down a column/group in PT?
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As you go down a column/group in PT, the electronegativity decreases. You would expect this because IE decreases while EA stays about the same.
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What is the trend for electronegativity as you go horizontally across a row in PT?
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As you go horizontally across a row in PT, the electronegativity increases going from left to right. This makes sense because as you go from left to right the IE increases and the EA increases in magnitude (becomes more negative).
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What is a dipole-dipole moment?
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A dipole-dipole moment occurs whenever a distance separates two electrical charges of equal magnitude but opposite signs.
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What is a nonpolar covalent bond?
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A nonpolar covalent bond is where the electrons are equally shared between two atoms in the covalent bond.
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Why do polar molecules form (not ionic compounds, which is very close to polar compounds but not the same thing)?
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Polar molecules form due to the polar covalent bonds between them. A polar molecule is a molecule in which the centers of positive and negative charge do not coincide. This occurs because one atom in the molecular bond has a higher electronegativity than the other atom in the bond. The atom with the higher EN attracts more electrons to it than the atom with the lower. Whichever atom attracts more electrons to it will have a slightly negative charge due to the charge of so many electrons. Conversely, the atom that does not attract so many electrons to it will have a slightly positive charge. Thus, a polar molecule forms.
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