Saturday, 23 October 2010

Electronic Structure In Shells

L.O. Define what a shell is.
L.O. Understand how they’re filled.
L.O. Explain and Describe the different types of bonding.

Neil’s idea of Levels became outdated and out-fashioned because it was too simple. This is when the idea of Shells came in.
Shells are groups of orbitals.
This is a more complex concept because the levels idea only includes distance measurements – but no shape or location values …etc
N=1 is the first shell. Contains 2 electrons.
N=2 is the second shell. Contains 8 electrons.
N=3 is the third shell. Contains 18 electrons.
Etc
You can only get S orbitals in n=1.
You can only get S and/or P orbitals in n=2.
You can only get S and/or P and/or D orbitals in n=3.
Etc
Atomic Number
N=1
N=2
N=3
N=4
Hydrogen
1
1



Helium
2
2



Lithium
3
2
1


Beryllium
4
2
2


Boron
5
2
3


Carbon
6
2
4


Nitrogen
7
2
5


Oxygen
8
2
6


Fluorine
9
2
7


Neon
10
2
8


Sodium
11
2
8
1

Magnesium
12
2
8
2

Aluminium
13
2
8
3

Silicon
14
2
8
4

Phosphorus
15
2
8
5

Sulfur
16
2
8
6

Chlorine
17
2
8
7

Argon
18
2
8
8

Potassium
19
2
8
8
1
Calcium
20
2
8
8
2
Scandium
21
2
8
9
2
Titanium
22
2
8
10
2
Vanadium
23
2
8
11
2
Chromium
24
2
8
12
1
Manganese
25
2
8
13
2
Iron
26
2
8
14
2
Cobalt
27
2
8
15
2
Nickel
28
2
8
16
2
Copper
29
2
8
18
1
Zinc
30
2
8
18
2
Gallium
31
2
8
18
3
Germanium
32
2
8
18
4
Arsenic
33
2
8
18
5
Selenium
34
2
8
18
6
Bromine
35
2
8
18
7
Krypton
36
2
8
18
8

n.b. The Group Number of an element is equal to the amount of electrons in its outermost shell.
Ionic Bonding
Covalent Bonding
Metallic Bonding
A metal, and a nonmetal
2 non metals
2 metals
Gain or loss of electrons
Sharing electrons
Sharing electrons
The objective of any bonding process is for atoms to become stable via filling their outermost shells.

Polarity & Electronegativity

The electron pairs shared between two atoms are not necessarily shared equally.
Bond polarity is a useful concept for describing the sharing of electrons between atoms.
A non-polar covalent bond is one in which the electrons are shared equally between two atoms.
A polar covalent bond is one in which one atom has a greater attraction for the electrons than the other atom. If this relative attraction is great enough, then the bond is an ionic bond.
Electronegativity of an atom is its ability to attract electrons to itself.
Dative bonding is when one element in a compound donates both electrons required for the bond to take place.
An example of this is Nitrous Oxide.
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