Group 16

Question 1

What types of elements does group 16 contain?

Answer 1

Non-metals, semi-conductors and metallics.

Question 2

What is catenation?

Answer 2

Bonding of the same element in series to form a chain..

Question 3

What is the maximum oxidation state for group 16?

Answer 3

+6.

Question 4

What are the common oxidation states of oxygen?

Answer 4

-2, -1 and 0.

Question 5

What is a triplet ground state?

Answer 5

The idea that the element has two spins of a half, and the total spin is defined as 2s+1 = 3.

Question 6

What are the properties of oxygen when solid or liquid?

Answer 6

Pale blue - at low temperatures.

Question 7

Why is oxygen paramagnetic?

Answer 7

It contains two unpaired electrons in its MO diagram.

Question 8

What is the significance of the higher Zeff in oxygen than nitrogen?

Answer 8

The s orbital is dragged down further in energy than the P - there is no s-p mixing.

Question 9

How is ozone prepared?

Answer 9

Electrical discharge through O2.

Question 10

What is the bond order of o-o bonds in O3?

Answer 10

1.5 - there is a half bond per O-O.

Question 11

What is the bonding in ozone?

Answer 11

The central O is sp2 hybridised - there is a lone pair of electrons in an Sp2 hybrid and a lone pair of electrons in a p orbital. There is a total of 4 electrons in p orbitals.

Question 12

What is the bond length in ozone?

Answer 12

Shorter than a single bond but longer than a double bond.

Question 13

Is oxygen or ozone a stronger oxidising agent?

Answer 13

Ozone - has a higher Eo.

Question 14

Why does elemental S have many allotropic forms?

Answer 14

It has a large number of rings and that can be formed with S-S bonds and the many ways they can pack in the solid state.

Question 15

What happens if you heat S8?

Answer 15

It melts and forms a yellow liquid (119 degrees) and then if it is continued to be heated to 159 degrees the viscosity increases dramatically. THe s8 rings open to form S8 chains. These interact to form S16, S24 etc and then if it is heated further the viscosity decreases again.

Question 16

Why is N2 more stable than P2 is they both have a short triple bond?

Answer 16

THe bond energy of N2 is more than 3x that for a N-N single bond. N-N allotropes are unstable with respect to N2. P2 does not show this property.

Question 17

What happens to atom size down the group?

Answer 17

It increases, and therefore atom-atom contact also increases.

Question 18

What happens to bond strength down the group and why?

Answer 18

As atom size increases, the size of the orbitals also increases and the distance them increases. The bond strength therefore also decreases.

Question 19

Why does the bond energy across the period decrease for N O and F?

Answer 19

The presence of lone pairs and the small size of the atoms causes stronger repulsions.

Question 20

What happens to acidity down a group of EH compounds?

Answer 20

It increases as the bonds are weaker and there is a greater tendency to form H+.

Question 21

Why is S2 made up of two sigma bonds whereas O2 is made up of a sigma and pi?

Answer 21

The pi component for O2 is greater than the sigma component - this is not true for S2 so it is more energetically favourable to have 2 sigma bonds.

Question 22

What happens to the energy differences between s and p orbitals down the group?

Answer 22

The energy difference increases and there is less s-p mixing and the bonds become more p like in character.

Question 23

Why does the boiling point of S to Te increase?

Answer 23

There is more Van der Waal’s forces.

Question 24

What are the properties of water?

Answer 24

The solid has a lower density than the liquid so ice floats, there are least 9 different forms at atmospheric pressure and 0 degrees, hexagonal ice exists.

Question 25

What are the properties of H2O2?

Answer 25

It is a very pale blue liquid with a boiling point of 150 degrees, it is a liquid at room temperature and is more viscous and dense than H20, the oxidation state is -1 and it can be both a strong oxidising and reducing agent.

Question 26

What is the only halide possible for oxygen?

Answer 26

Fluoride.

Question 27

What are the properties of OF2?

Answer 27

It is a colourless gas that is toxic and undergoes rapid decomposition to F2 and O2.

Question 28

What is the boiling point of OF2?

Answer 28

-145 degrees celsius.

Question 29

What are the properties of OFH?

Answer 29

It is a colourless liquid that is very toxic. It decomposes to HF and O2 at room temperature.

Question 30

What is the boiling point of OFH?

Answer 30

29 degrees celsius.

Question 31

How can O2F2 be prepared?

Answer 31

Passing electrical discharge through F2 and O2.

Question 32

What do elements below the top row have the ability to do?

Answer 32

Expand the octet/show hypervalency.

Question 33

What was the old argument for why the second row elements show hypervalency?

Answer 33

Electrons went into d orbitals - this is wrong as there is a huge energy gap.

Question 34

What is the modern idea for why second row elements show hypervalency?

Answer 34

The additional electrons go into non-bonding orbitals.

Question 35

Why is SF6 stable?

Answer 35

The fluorine atoms surrounding the sulfur stop attack at the centre.