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23 Cards in this Set
- Front
- Back
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Describe the octet rule.
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Atoms tend to gain , lose or share electrons to ultimately end up with eight valence electrons.
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What is lattice energy ?
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The amount of energy needed to completely separate a mole of a solid ion into its gaseous ions.
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What is responsible for the energy released during the formation of an ionic compound ?
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The strong attractive forces between the ions of unlike charge.
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What are the two factors that influence the lattice energy ?
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1. Magnitude of charges on ions
2. Atomic radii of ions |
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Describe the loss of electrons, in terms of valence shells, of transition metals when they becomes ionic compounds.
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They will first lose all their electrons in the outer most S orbital, then they will lose electrons in their outer most D orbital which is required.
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What is the bond called where atoms 'share' electrons ?
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A covalent bond.
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What is the relationship between bond length and the amount of bonds ?
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The bond length decreases as the amount of bonds increases.
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What is a nonpolar covalent bond ?
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When the electrons between two atoms are shared equally.
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What is a polar covalent bond ?
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When a atom in a covalent molecule has a greater force of attraction on the electrons being shared.
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True or false: When there is a huge difference in electronegativity between two atoms, a polar covalent bond is formed.
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False. If there is a large difference an ionic substance will form.
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Define electronegativity.
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The ability of an atom in a molecule to attract electrons to itself.
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What can you deduce, in terms of electronegativity, from an atom that has a high ionisation energy and a high electron affinity ?
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It has a high electronagtive value.
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What is the trend for electronegativity on the periodic table ?
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1. Decreases moving down a group
2. Decreases moving from let to right in a period |
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What happens during a dipole ?
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Two positive and negative charges of equal magnitude are separated a small distance.
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Give the equation for a dipole moment.
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u = qr.
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How would you go about drawing lewis structures ?
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1. Sum up the valence electrons
2. Put the least electronegative atom in the middle 3. Arrange all the other atoms around that single atom 4, Complete the octets of the atoms around the central atom 5. Now arrange all the remaining electrons around the central atom, and give/take bonds to fill its octet |
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How do you calculate an atom's formal charge ?
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Subtracting the amount of electrons around the atom with its total number of valence electrons.
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How do you choose the right Lewis structure using formal charges ?
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1. Choose the structure with the charges closest to zero
2. Choose the structure where negative charges reside on more elctronegative atoms |
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In which cases does the octet rule fall short ?
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When an atom or molecule:
1. Has an uneven amount of electrons 2. More than 8 valence electrons 3. Less than 8 valence electrons |
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What is bond enthalpy ?
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The change in enthalpy required to break down a bond in one mole of a gaseous substance.
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What is the relationship between chemical stability and bond strength ?
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The stronger the bonds, the more chemically stable the molecule.
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True or false: Breaking down bonds is always an exothermic process.
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False. Breaking down bonds is always an endothermic process and forming new bonds is always an exothermic process.
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How would you calculate overall enthalpy ?
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The sum of the bonds broken minus the sum of the bonds formed.
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