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52 Cards in this Set
- Front
- Back
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Why do atoms bond together?
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To achieve lowest possible potential energy. For example H2, Br2, F2, I2, Cl2, N2
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how do Lewis Dot Structures work?
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Symbol for an element and dots indicating how many valence electrons it has. Valence electron # being the group it's in.
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How do you tell when something is ionic?
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Ionic compounds are anything that, when melted, conducts electricity.
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there is ____ attraction between oppositely charged ions
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Electrostatic
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Ions are packed together to minimize... maximize...
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minimize repulsion, maximize attraction
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Electron Affinity
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Energy change that occurs when electron is accepted by an atom in the gaseous state, the greater the electron affinity the more likely it'll accept an electron
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Chlorine has the lowest...
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electron affinity
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Lattice Energy
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The energy released when an ionic solid forms from its ions.
or The energy required to separate one mole of a solid ionic compound into gaseous ions |
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The Born-Haber Cycle for determining Lattice Energies
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Relates lattice energies into ionization energies, electron affinities, and other atomic and molecular properties
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To form ionic compounds...
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the lattice energy must be larger than the ionization energy that forms a cation.
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Valence Electrons
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are the electrons in the highest occupied energy level of an element's atoms (outside of core). The valence electron can be determined by the group number. 1A, 2A, 3A, etc.
(Note: Noble gases are exceptions. Helium has two, all others have eight) |
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Electron dot structures
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depict valence electrons as dots. The inner electrons and the atomic nuclei are represented by the symbol for the element being considered.
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Why are some elements found mainly as ions?
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Because the nature of things is to adjust to achieve the lowest possible energy (potential energy).
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The higher the chemical reactivity...
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the more unstable the electron configuration.
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1916, Gilbert Lewis:
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provided explanation for why atoms tend to form certain types of ions and molecules by proposing the octet rule: Atoms react by changing the number of their electrons so as to acquire the stable electron structure of a noble gas.
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Octet rule:
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That the ions always have 8 electrons at its highest level
(ex: Na has 1 valence electron, when it loses it, it has the same electron configuration as neon, a noble gas, therefore the Na ion has 8 electrons in hits highest energy level.) |
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Some exceptions of the octet rule:
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would be those that can't acquire a noble-gas configuration though they'd still get a relatively stable configuration. Ions of Cu, Ag (silver), AU, CD and HG have pseudo noble-gas electron configurations
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Anions of chlorine and the other halogens gain electrons to form
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halide ions. Halogens have seven valence electrons, thus, they need to gain one electron to achieve the electron configuration of a noble gas.
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ionic bonds
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are the forces of attraction that bind oppositely charged ions together, ionic COMPOUNDS are electrically neutral groups of ions joined by electrostatic forces, also known as salts. In an ionic compound, the positive charges must equal the negative charges.
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A Formula Unit, or better known as a FU
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represents the smallest sample of an ionic compound that has the composition of the compound.
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Most ionic compounds are crystalline solids at room temperature, it is packed such that
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there's maximized attraction and minimized repulsion.
(Ionic compounds all conduct electric current at its molten state and can produce electric conductivity when dissolved in water.) |
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The coordination number...
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gives the number of ions of opposite charge that surrounds each ion in a crystal
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Metallic bonds...
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consists of the attraction of the free-floating valence electrons for the positively charged metal ions. (metals have good conductivity, they're malleable) They are ductile, can be drawn into wires. When subjected to pressure, they'll slide past one another, whilst ions, it'll force like charges to contact, and the crystal will shatter.)
(Note:It is said that pieces of pure metals consists o not metal atoms, but closely packed cations which are surrounded by mobile valence electrons) |
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Metals are the simplest crystalline solids, they contain one kind of atom, they're arranged in a compact and orderly pattern.
In a body-centered cubic structure... In face-centered cubic arrangement... In hexagonal close-packed arrangement... |
BC: Every atom (except the ones on the surface) has eight neighbors. Elements: Na, K, Fe, Cr, and Tungsten are that.)
FC: Has 12 neighbors. (Cu, Ag (silver), Au, Al, and Pb) HC: Every atom has 12 neighbors. Pattern is different from face-centered cube. They have crystal structure (Mg, Zn, and Cd) |
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Covalent Bonds
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are the result of electron-sharing between atoms. Atoms of hydrogen and nonmetallic elements in Groups 4A, 5A, 6A, 7A are particularly prone to form covalent bonds.
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In a Covalent Bond, the configurations contain eight valence electrons (an octet) w/ the notable exception of
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hydrogen. When hydrogen shares two electrons it acquires the stable electron configuration of helium.
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A single covalent bond is
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formed when a pair of electrons is shared between two atoms.
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Structural formulas
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are chemical formulas that show the arrangement of atoms in molecules and polyatomic ions. The chemical formulas are formula units. Chemical formulas of covalent compounds are molecular formulas.
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The pairs of valence electrons that are not shared between atoms are called
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unshared pairs of electrons, or UNSHARED PAIRS. They're also called lone pairs, or nonbonding pairs.
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Double covalent bonds involve
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two shared pairs of electrons, while triple covalent bonds involve 3 pairs of shared electrons.
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When one atom contributes both bonding electrons in a covalent bond, a
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coordinate covalent bond is formed. Many polyatomic cations and anions contain covalent and coordinate covalent bonds.
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Double covalent bonds are usually ____ than single covalent bonds
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shorter, but in ozone, they are the same length since actual bonding in ozone molecule is the average of the two electron dot structures.
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Resonance occurs when
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two or more equally valid dot structures can be written for a molecule.
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Substances were all the electrons are paired are said to be
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diamagnetic
(diamagnetic substances are weakly repelled by an external magnetic field.) |
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Paragmagnetic
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show relatively strong attraction to an external magnetic field. Can be detected by measuiring pass of a substance in the absence and then the presence of a magnetic field. The mass will be greater w' the magnetic field if it's paramagnetic.
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Ferromagnetism
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much stronger attraction of iron, cobalt and nickel for magnetic field. All unpaired electrons, permanent magnetism.
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There are some exceptions
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oxygen, boron, phosophorus, sulfur, etc.
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When two atoms combine, their atomic orbitals overlap to produce
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molecular orbitals
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A molecular orbital whose energy is lower than that of the atomic orbitals from which is formed is a
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bonding orbital
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A molecular orbital whose energy is higher than that of the atomic orbital is the
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antibonding orbital.
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a Sigma Bond is formed when
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two atomic orbitals combine to form a molecular orbital that is symmetrical along he axis connecting two atomic nuclei.
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VSEPR theory
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states that because electron pairs repel, molecules adjust their shape so that the valence-electron pairs are as far apart as possible.
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When the atoms in a molecule are the same, the bonding electrons are shared equally, and the bond is a
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nonpolar covalent bond
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when two different atoms are joined by a covalent bond, and the bonding electrons are shared unequally, the bond is is a
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polar covalent bond or simply a polar blond. The more electronegative an element the more negative it gets. (pulls on the electrons tighter)
We use the delta sign delta + and delta - to indicate the differences. Or you can use the arrow with the perpendicular line on the end where it's slightly more positive. |
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In a polar molecule, one end of the molecule is
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slightly negative, and one end is slightly positive
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A molecule that has two poles is called a
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dipolar molecule, or dipole.
(ex: The hydrogen chloride molecule is a dipole) |
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The energy required to break a single bond is known as the
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bond dissociation energy.
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The intermolecular attractions are always present despite it being weaker than the ionic and covalent bonds. The weakest is called the
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van der Waals forces, after Dutch chemist Johannes van der Walls. There are two of them, dispersion forces and dipole interactions
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Dispersion forces
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the weakest of all molecular interactions, are thought to be caused by the motion of electron. (Strength increase as the number of electrons in a molecule increases.)
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Dipole interactions
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occurs when polar molecules are attracted to one another. When oppositely charged regions of dipolar molecules attract one another.
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Hydrogen Bonds
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are attractive forces in which a hydrogen that is covalently bonded to a very electronegative atom is also weakly bonded to an unshared electron pair of an electronegative atom in the same molecule or in a nearby molecule.
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Most are very stable substances that are ______ in which all of the atoms are covalently bonded to each other
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network solids.
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