Chemistry ch 12
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Chemistry ch 12
the tendancy of an atom,
which is bonded with other atoms
, to attract other electrons
what is EN related to?
postion on the periodic table
Down- EN decreases
Across- EN increases
how strong the bond is
EN of active metals
En of active nonmetals
EN of noble goases
Are atoms all covalent or all ionic?
No, it's the % ionic character
most are some of both
If En is greater than...
1.67, it's ionic
What if the EN is 1.67?
it's half and half
What holds the ions together in an ionic bond?
The electrostatic forces between + and -
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
Are ionic or covalent bonds stronger?
covalent bonds form
atoms of similar EN tend to
Do covalent bnonds have electrostatic forces?
No, they form molecules, not ions
a line joining the nuclei of covalently-bonded atoms
when one atom bonds with two other atoms, an angle is formed between two nuclei
the distance between two nuclei.
Is bond length always the same?
No, it varies
Why does bond length vary?
because covalent bonds stretch, bond, vibrate, and rotate.
How do scientisits know about the structure of molecules?
Characteristics of covalent compounds
1. low MP
2. don't conduct electricity
3. less soluable in water
4. don't form crystals- tend to be
brittle solids, liquids, or gases
Metals form crystals when
8-12 atoms of the same metal surround another metal atom
why don't metals want to bond covalently?
they want to lose 1-3 electrons
why don't metals form ionic bonds?
they all have the same attraction for their electrons
metallic bonds form when
metallic atoms crowd together and
their outer energy levels overlap
what cause the characteristics of metals?
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
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
what holds the atoms together in a metallic bond?
1 outer electron
the bond isn't as strong, and the metal is soft
alkaline earth metals
2 outer electrons
bonds are stronger, and the metal is harder
2 outer electrons & 1 or more d electrons
uniformly combine 2 or more metals to form
new and more usable substances
alloys are not a..
chemical change, but rather a physical blending
Cu & Zn
Cu & Sn
Fe & C
Fe, C, Cr, & Ni
42% Ag & 58% Au
Ag & Cu
add the radii of the ions to find the distance between the nuclei
why are ionic radii difficult to measure?
their electron clouds make the distance hard to measure
difference between ionic and covalent bonds
in covalent bonds,
energy levels overlap to share one or more pairs of electrons
H + H = H2
covalent bond lengths are almost always how long in comparison to the atomic radii?
less than the combining radii.
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
van der Waals radius
the distance from the nucleus to the wall or shell from the electron cloud
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