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123 Cards in this Set
- Front
- Back
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Waves
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the means by which electromagnetic radiation is carried through space, an oscillation that moves outward from a disturbance.
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Electromagnetic Waves
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need no medium through which to travel, they can cross empty space. the speed at which it travels is roughly 3 x 10^8 m/s.
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Amplitude
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of a wave is related to the intensity or brightness of the radiation.
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Frequency
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number of cycles per second
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Wave Length
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peak to peak distance
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Speed of Light
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the speed of electromagnetic radiation in a vaccum, 3 x 10^8 m/s.
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Meter
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is defined as the distance light travels in 1/299,792,458 of a second.
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Objects can have energy....
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in only two ways, potential and kinetic.
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Amplitude of a wave is...
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related to the intensity or brightness of the radiation.
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The number of cycles per second...
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is the frequency, it's symbol is v (pronounced nu). one Hz is one cps.
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Peak to peak distance....
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is called wavelength, it's symbol is lambda.
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Speed of light
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is 3 x 10^8 m/s
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nu equals...
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c divided by lambda (speed of light constant divided by wavelength)
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EM Spectrum
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gamma (shortest) ---> x rays --> UV --> Visible --> IR --> Microwaves --> Radio and TV (longest)
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Visible Spectrum
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Violet (~400nm) --> I --> B --> G --> Y --> O --> Red (~700nm)
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The Energy of a Photon of EM Radiation...
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is proportional to it's frequency (not it's intensity or brightness) E = hv (h = planck's number - 6.626 x 10^-34 and v (nu) = frequency.
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Brighter light delivers more photons but...
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higher frequency light delivers more energetic photons.
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Continuous Spectrum
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contains a continuous unbroken distribution of light of all colors, as opposed to an atomic spectrum (or emission spectrum) which emits individual lines of particular colors that are unique to the atoms which are excited.
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Atomic Energy is Quantized
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meaning that, when a particular atom is excited it releases a very specific amount of energy (as it's electrons move from low to high energy), not an arbitrary amount. The same is true when it absorbs energy. The electrons are restricted to certain energy levels.
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The energy changes for a e-...
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are restricted by the differences in potential energies between energy levels.
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Ground state
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lowest and most stable energy state of an atom.
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The wavelength of a matter wave...
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equals planck's constant divided by mass times velocity. connects wave and particle properties.
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The reinforcement and cancellation of wave intensities is called...
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diffraction
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Nodes
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points of zero amplitude, have a fixed position
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Wave Function
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symbolized by psi, describes the shape of the electron wave (orbital) and its energy.
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Orbitals
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wave functions for electrons in atoms
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Energy changes within an atom...
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are the result of an electron changing from a wave pattern with one energy to a wave pattern with a different energy
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n
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the principal quantum number, all orbitals with the same n value are in the same shell. ranges from one to infinity. the higher the value of n the greater the electron's average distance from the nucleus. as n increases the energy of the orbitals increases.
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l
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the second quantum number (aka azimuthal or orbital angular momentum number) divides the shells into subshells, n determines which l values are allowed, can range from 0 - (n-1),
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l values and letters
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l = 0 -- s
l = 1 -- p l = 2 -- d l = 3 -- f l = 4 -- g l = 5 -- h |
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Relationship between n and l
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n = 1 -- l = 0
n = 2 -- l = 0,1 n = 3 -- l = 0,1,2 n = 4 -- l = 0,1,2,3 n = 5 -- l = 0,1,2,3,4 n ranges from 0 - (n-1) |
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Designating Subshells
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if n=1 and l = 0 -- 1s
if n = 1 and l = 1 -- 2p if n = 3 and l = 2 -- 3d |
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The number of subshells in a given shell...
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equals the value of n for that shell. example: n=3 has 3 subshells (0,1,2)
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m sub l
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magnetic quantum number, indicates orbitals within a subshell, values range from +l to -l,
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Number of orbitals in a subshell...
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s - 1
p - 3 d - 5 f - 7 |
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An atom in its ground state...
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is at its most stable
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m sub s
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spin quantum number, can be either -1/2 or + 1/2,
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Pauli Exclusion Principle
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no two electrons in the same atom can have identical values for all four of their quantum numbers. the maximum in any orbital is two and they must have opposite spins.
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Subshells, Orbitals, Electrons
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s has 1 orbital and 2 e-
p has 3 orbitals and 6 e- d has 5 orbitals and 10 e- f has 7 orbitals and 14 e- |
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When 2 e- occupy the same orbital...
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they must have different m sub s values, when this happens their "spins are paired"
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Unpaired e-
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result in paramagnetism.
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Paramagnetism
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the weak attraction of a substance containing unpaired electrons to a magnet.
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Diamagnetism
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all electrons are paired, not attracted to a magnet. objects that are diamagnetic are actually weakly repelled by a magnetic field.
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The distribution of electrons in the orbitals of an atom...
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is called its electronic structure or electron configuration. this arrangement determines the chemical properties of elements.
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aufbau principle
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from german for "building up", states that when filling orbitals electron must be added one at a time to the lowest available orbital until enough have been added to give a neutral atom of the element in question.
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Hund's Rule
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when electrons are placed in a set of orbitals of equal energy they are spread out as much as possible to give as few paired electrons as possible. place them in one orbital at a time until all have one, then go back to the start and add to each level.
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Groups and Periods
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groups are vertical, periods horizontal.
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s orbitals
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are spherical, going out any distance in any direction there is an equal probability that we will find an e-. s orbital's spherical size increases with the value of n. nodes are present like layers in a gobstopper, where the colors change there is a 0.00 chance of finding an e-
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p orbitals
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2 lobed. e- density is equally distributed in two regions on opposite sides of the nucleus.
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Nodal Plane
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area between lobes, an imaginary flat surface on which every point has an electron density of 0.
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Atomic size
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varies periodically, largest in the lower left of the table and smallest in the upper right.
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Ionization Energy
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energy required to remove an electron from an isolated, gaseous atom or ion in its ground state. larger atoms have lower IE.
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Electron Affinity
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the potential energy change associated with the addition of an electron to a gaseous atom or ion in its ground state. Low IE = Small EA
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Ionic Bond
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the attraction between positive and negative ions in an ionic compound
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For any stable compound to form from its elements...
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there must be a net lowering of potential energy, the reaction must be exothermic.
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Endothermy and Exothermy...
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are an increase in PE and a decrease in PE respectively.
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Octet Rule
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atoms tend to gain or lose electrons until they have reached an outer shell that contains eight electrons.
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Obtaining the e- Configuration of an ion
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the first e- to be lost are those in the shell with the largest value of n, electrons are removed starting with the highest energy subshells first.
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For any stable compound to form from its elements...
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there must be a net lowering of PE
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Lattice Energy
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the energy required to completely separate the ions in one mole of a solid compound from each other to form a cloud of gaseous ions. It also provides the stabilization necessary to from solids from gases.
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For an ionic compound to be formed...
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the exothermic release of the lattice energy must be larger than the endothermic combination of factors involved in the formation of the ions themselves.
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As ions become smaller...
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their lattice energy increases, smaller ions allow the charges to get closer together which makes them more difficult to pull apart.
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Metals form cations and non-metals form anions because...
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metals have small IEs and EAs so relatively little energy is needed to remove electrons from them to produce positive ions. It is least expensive to form a cation from a metal.
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The net force of attraction produced by electron sharing is...
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called a covalent bond.
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Every covalent bond is characterized by two quantities...
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the average distance between the nuclei held together by the bond and the amount of energy needed to separate the two atoms to produce neutral atoms again. Bond length and bond energy respectively.
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As the distance between the nuclei and the electron cloud that lies between them decreases...
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the potential energy decreases.
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Hydrogen forms..
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only one covalent bond
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When atoms form covalent bonds...
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they tend to share sufficient electrons so as to achieve an outer shell having eight electrons.
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When atoms form covalent bonds...
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they tend to share sufficient electrons so as to achieve eight electrons in their outer shell (OCTET)
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Hydrogen...
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forms a single covalent bond.
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A bond that carries partial positive and negative charges on opposite ends is called...
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a polar covalent bond.
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Dipole moment
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is equal to the amount of charge on either end of the molecule multiplied by the distance between the charges.
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The attraction an atom has for the electrons in a bond...
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is called its electronegativity.
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The difference in electronegativity...
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provides an estimate of the degree of polarity of a bond.
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The less electronegative end of a molecule...
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carries the partial positive charge.
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A bond is mostly ionic...
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when the difference in electronegativity between the two atoms is very large.
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In a nonpolar covalent bond...
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there is no difference in electronegativity.
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A bond becomes more than 50% ionic...
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when the electronegativity difference exceeds ~1.7
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Electronegativity increases...
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from bottom to top in a group, and from left to right in a period (same as IE)
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When the difference in electronegativity is small..
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the bond will be mostly covalent.
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Electronegativity is proportional...
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to the average of the IE and the EA.
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The reactivity of a metal...
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refers to its tendency to undergo oxidation (its ability to serve as a reducing agent)
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Lewis Structures
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1. Decide which atoms are bonded to each other.
2. Count all valence e- 3. Add or remove e- to account fo net charges. 4. Place TWO e- in each bond. 5. Complete the octets of the atoms attached to the central atom by adding e- in pairs. 6. Place any remaining e- on the central atoms in pairs. 7. If the central atom has less than an octet form 2x bonds, if necessary from 3x bonds. |
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In oxoacids...
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the hydrogen atoms that can be released from molecules of oxoacids are always bonded to oxygen atoms, which are in turn bonded to the third nonmetal atom.
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Bond Order
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number of pairs of electrons shared between two atoms.
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As bond order increases...
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bond length decreases and bond energy increases, provided we are comparing bonds between the same elements.
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The apparent charge on an atom...
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is its formal charge.
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Formal Charge
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equals the number of electrons in the valence shell of an isolated atom minus (the number of bonds to the atom plus the number of unshared electrons)
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The formal charges in any lewis structure...
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add up to the net charge on the particle.
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The number of resonance structures...
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is equal to the number of equivalent choices for the locations of the double bonds.
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Linear Molecule
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atoms lie in a straight line, the bond angle is 180 degrees. one central atom and 2 bonded atoms attached at opposite ends.
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Planar Triangular
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three atoms are located at the corners of a triangle and are bonded to a fourth central atom that lies in the center. the bond angle is 120 degrees.
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Tetrahedron
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four sided, shaped like a pyramid, four atoms located at the vertices of a tetrahedron are bonded to a fifth atom in the center of the structure. the bond angles are 109.5 degrees.
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Trigonal Bipyramidal
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consists of 2 trigonal pyramids that share a common base, the angle between equatorial bonds is 120 degrees and the angle between axial and equatorial is 90 degrees.
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Octahedron
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eight sided, consists of two square pyramids sharing a common base, all bond angles 90 degrees.
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VSEPR
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valence shell electron pair repulsion model, based on the idea that groups of electrons in the valence shell of an atom repel each other and will position themselves in the valence shell so that they are as far apart as possible.
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Bonding Domain
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contains electron pairs that are involved in bonds between a pair of atoms, all electrons within a given bond (be it single, 2x or 3x) are in the same bonding domain.
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Non-Bonding Domain
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contains valence electrons that are associated with a single atom, can be an unshared pair of valence electrons (called a lone pair) or a single unpaired electron.
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Domains and Shape
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2 domains - linear
3 domains - planar triangle 4 domains - tetrahedron 5 domains - trigonal bipyramidal 6 domains - octahedral |
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A molecule will be nonpolar...
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if the bonds are nonpolar or there are no lone pairs in the valence shell of the central atom and all the atoms attached to the central atom are the same.
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A molecule in which the central atom has lone pairs of electrons...
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will usually be polar.
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According to the VB theory, a bond between 2 atoms is formed...
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when two electrons with their spins paired are shared by two overlapping atomic orbitals, one orbital from each of the atoms joined by the bond.
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Sigma Bond
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a bond in which the electron density is concentrated most heavily between the nuclei of the two atoms along an imaginary line that joins their centers, end to end overlap.
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Pi Bond
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a bond in which the electron density is divided between two separate regions that lie on opposite sides of an imaginary line joining the two nuclei, allows for 2x and 3x bonds. sideways overlap.
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A 2x bond...
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consists of a sigma and a pi.
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A 3x bond...
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consists of a sigma and 2 pi.
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The basic molecular framework of a molecule...
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is determined by the arrangement of its sigma bonds.
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Hybrid orbitals are used by an atom...
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to form its sigma bonds and to hold lone pairs.
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The number of hybrid orbitals needed by an atom in a structure...
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equals the number of atoms to which it is bonded plus the number of lone pairs of valence electrons. (bonding domains + non-bonding domains)
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2 Bonding Domains -- 0 Non Bonding Domains
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Structure -- Linear
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2 Bonding Domains -- 1 Non Bonding Domain
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Structure -- Bent
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3 Bonding Domains -- 0 Non Bonding Domains
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Structure -- Planar Triangular
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3 Non Bonding Domains -- 1 Non Bonding Domain
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Structure -- Trigonal Pyramidal
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2 Bonding Domains -- 2 Non Bonding Domains
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Structure -- Trigonal Pyramidal
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4 Bonding Domains -- 0 Non Bonding Domains
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Structure -- Tetrahedral
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5 Bonding Domains -- 0 Non Bonding Domains
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Structure -- Trigonal Bipyramidal
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4 Bonding Domains -- 1 Non Bonding Domain
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Structure -- Distorted Tetrahedral
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3 Bonding Domains -- 2 Non Bonding Domains
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Structure -- T-Shaped
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2 Bonding Domains -- 3 Non Bonding Domains
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Structure -- Linear
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6 Bonding Domains -- 0 Non Bonding Domains
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Structure -- Octahedral
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5 Bonding Domains -- 1 Non Bonding Domain
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Structure -- Square Pyramidal
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4 Bonding Domains -- 2 Non Bonding Domains
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Structure -- Square Planar
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