Group 15- The Pnictogens

Question 1

What is the outer electron configuration?

Answer 1

ns2np3

Question 2

Which compounds can N and P form?

Answer 2

They can form trianion nitrides with the oxidation state -3

Question 3

Which oxidisation states are most common?

Answer 3

+5 and +3

Question 4

When are nitrogen(V) compounds possible?

Answer 4

Nitrogen (V) compounds are only possible in compounds containing multiple bonds (e.g. Nitrate ions)
The nitrogen atom has charge +1

Question 5

Describe the different in IE of np and ns

Answer 5

Np ionisation energy is much less than ns as s electrons are held closer to the nucleus

Question 6

Describe the trend in IE

Answer 6

There is a small bump due to the filling of d orbitals

Question 7

Why is N5+ rare?

Answer 7

The high ionisation energy of s electrons in nitrogen means that they tend not to become involved in bonding

Question 8

Why is n triple bond generally unreactive?

Answer 8

The multiple bonds are strong
There is a large homo-lumo gap which prevents oxidation or reduction
It has a low polarisability which prevents attack by electrophiles and nucleophiles

Question 9

Why is P4 more stable than P2 and N2 more stable than N4?

Answer 9

This is because as you do down the group, multiple bond strength decreases
Smaller elements form strong multiple bonds due to good overlap
But smaller elements form weak single bonds due to strong electron repulsions
The reverse is true for large elements