Electrons and Bonding

Number of electrons in the first 4 shells

• First shell = 2

• Second shell = 8

• Third shell = 18

• Fourth shell = 32

Atomic orbital

A region around the nucleus that can hold up to 2 electrons with opposite spins

Describe the shape of an s-orbital

Spherical

Describe the shape of a p-orbital

Dumbbell

Number of s-orbitals in an s sub-shell

1

Maximum number of electrons an s sub-shell can hold

2

Number of p-orbitals in a p sub-shell

3

Maximum number of electrons a p-subshell can hold

6

Number of d-orbitals in a d sub-shell

5

Maximum number of electrons a d sub-shell can hold

10

Number of f-orbitals an f sub-shell

7

Maximum number of electrons an f sub-shell can hold

14

How are orbitals filled?

Each orbital has one electron then they are paired up

Ionic bonding

The strong electrostatic attraction between positive and negative ions

Describe the structure of giant ionic lattices

Oppositely charged ions strongly attracted in all directions

Why do ionic compounds have high melting and boiling points?

• Strong electrostatic attraction between oppositely charged ions

• Requires lots of energy to overcome forces

Why can ionic compounds conduct electricity when molten but not when solid?

• Solid = ions are in fixed position & aren’t free to move to carry charge

• Molten = ions are free to move and can carry charge

Covalent bond

Strong electrostatic attraction between shared electron pair and the nuclei of the bonded atoms

Dative covalent bond

• The shared pair of electrons has been supplied by 1 atom only

• Electrons originally were a lone pair on the atom

Average bond enthalpy

• Measurement of covalent bond strength

• The larger the average bond enthalpy, the stronger the covalent bond