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Electronegativity
the tendancy of an atom, which is bonded with other atoms, to attract other electrons
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what is EN related to?
- postion on the periodic table
- Down- EN decreases
- Across- EN increases
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bond strenght
how strong the bond is
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En of active nonmetals
High
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Are atoms all covalent or all ionic?
- No, it's the % ionic character
- most are some of both
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If En is greater than...
1.67, it's ionic
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What if the EN is 1.67?
it's half and half
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What holds the ions together in an ionic bond?
The electrostatic forces between + and -
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Characteristics of ionic compounds
- 1. High MP
- 2. don't conduct electricity as a solid, but do in their molten state, when dissovled in water, & as a gas
- 3. very soluable
- 4. usually form well-defined crystals (solids)
- 5. held together more strongly than compounds with covalent bonds
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Are ionic or covalent bonds stronger?
ionic
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covalent bonds form
molecules
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atoms of similar EN tend to
share electrons
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Do covalent bnonds have electrostatic forces?
No, they form molecules, not ions
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bond axis
a line joining the nuclei of covalently-bonded atoms
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bond angle
when one atom bonds with two other atoms, an angle is formed between two nuclei
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bond length
the distance between two nuclei.
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Is bond length always the same?
No, it varies
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Why does bond length vary?
because covalent bonds stretch, bond, vibrate, and rotate.
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How do scientisits know about the structure of molecules?
Infared spectroscopy
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Characteristics of covalent compounds
- 1. low MP
- 2. don't conduct electricity ever3. less soluable in water
- 4. don't form crystals- tend to be brittle solids, liquids, or gases
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Metals form crystals when
8-12 atoms of the same metal surround another metal atom
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why don't metals want to bond covalently?
they want to lose 1-3 electrons
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why don't metals form ionic bonds?
they all have the same attraction for their electrons
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metallic bonds form when
metallic atoms crowd together and their outer energy levels overlap
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what cause the characteristics of metals?
delocalized electrons
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characteristics of metals
- 1. very high MP
- 2. great conductors of electricity- the delocalized electrons carry the current
- 3. have luster
- 4. melleability and ductility
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why do metals have luster?
the electrons jump to a higher energy level when exposed to light and then drop back, giving off light as they do
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what holds the atoms together in a metallic bond?
delocalized electrons
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alkaili metals
- 1 outer electron
- the bond isn't as strong, and the metal is soft
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alkaline earth metals
- 2 outer electrons
- bonds are stronger, and the metal is harder
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transition metals
- 2 outer electrons & 1 or more d electrons
- very hard
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alloy
uniformly combine 2 or more metals to form new and more usable substances
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alloys are not a..
chemical change, but rather a physical blending
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stainless steel
Fe, C, Cr, & Ni
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14k gold
- 42% Ag & 58% Au
- (24k=pure Au)
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internuclear distance
add the radii of the ions to find the distance between the nuclei
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why are ionic radii difficult to measure?
their electron clouds make the distance hard to measure
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difference between ionic and covalent bonds
- in covalent bonds, energy levels overlap to share one or more pairs of electrons
- H + H = H2
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covalent bond lengths are almost always how long in comparison to the atomic radii?
less than the combining radii.
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why do free atoms repel each other?
- the repulsion of their respective electron clouds
- they clouds set up a wall or shell around each atom
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van der Waals radius
the distance from the nucleus to the wall or shell from the electron cloud
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Why do you add the van der waals radii?
adding the van der waals radii of teo different atoms shows the minimum distance these two atoms can be to each other
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