1.1 Periodicity

Question 1

How are elements arranged in the periodic table?

Answer 1

In order of increasing atomic number

Question 2

What are the covalent molecular elements?

Answer 2

H₂ , N₂ , O₂ , F₂ , I₂, Cl₂ , Br₂, P₄ , S₈ and fullerenes (eg C₆₀)

Question 3

What elements are covalent networks?

Answer 3

Boron, Carbon (diamond and graphite), Silicon.

Question 4

What are the monatomic elements?

Answer 4

The noble gases

Question 5

What is covalent radius a measure of?

Answer 5

The size of an atom

Question 6

What is the covalent radius?

Answer 6

The distance between an atoms nucleus and it’s outershell.

Question 7

How can trends in covalent radius across periods and down groups be explained?

Answer 7

in terms of the number of occupied shells, and the nuclear charge

Question 8

What is the trend in covalent radii across a period?

Answer 8

Covalent radii decreases across a period as there is an increase in the number of protons (and nuclear charge), This increasing nuclear charge means the electrons are pulled in more tightly, closer to the nucleus which makes the atom decrease in size.

Question 9

What is the trend in covalent radii down a group?

Answer 9

-increases
1. An extra shell of electrons is added therefore the electrons are further away from the nucleus.
2. Filled inner electron shells ‘screen/shield’ outer electrons from the attractive force of the nucleus therefore there’s less of an attraction between the nucleus and outer electrons so atomic radii increases.

Question 10

What is the first ionisation energy?

Answer 10

the energy required to remove one mole of electrons from one mole of gaseous atoms.

Question 11

What do the second and subsequent ionisation energies refer to?

Answer 11

The energy required to remove further moles of electrons

Question 12

What are the trends in ionisation energy across a period.

Answer 12

• 1st ionisation energy increases
• As there is an increase in the number of protons (nuclear charge) electrons are pulled in more tightly making them harder to remove

Question 13

What are the trends in ionisation energy down a group?

Answer 13

-decreases
1. there’s an extra shell of electrons added and electrons are further from the nucleus, the attraction of the nucleus for the electron becomes less and its easier to pull it away.
2. Filled inner electron shells ‘screen/shield’ outer electrons from attractive forces of the nucleus. Causing less of an attraction between the nucleus and outer electrons - making it easier to remove.

Question 14

Atoms of different elements have…

Answer 14

Different attractions for bonding electrons

Question 15

What is electronegativity a measure of?

Answer 15

The attraction an atom involved in a bond has for the electrons of the bond.

Question 16

What are the trends in electronegativity across a period?

Answer 16

-increases
- More protons are being added to the nuclei of atoms - increasing nuclear charge. This results in greater attractions between positively charged nucleus and negatively charged bonding electrons.

Question 17

What are the trends in electronegativity down a group?

Answer 17

-decreases
1. With every extra shell of electrons added, bonding electrons are further from the nucleus. The increase in distance reduces attraction between nucleus and bonding electrons.
2. Filled inner electrons ‘shield’ bonding electrons from nucleus reducing attractive force between positive nucleus and negative bonding electrons.