3.2.4 Period 3

What is periodicity?

repeating pattern of chemical and physical properties of element in the periodic table

Describe the trend in atomic radius of P3 going across

decreases

number of protons and nuclear charge increases

more electrons but shielding is negligible as each electron enters the same energy level

the EFA between the nucleus and electrons increases so atomic radius decreases

Describe first ionisation energy trend of P3 going across

increases

more protons so nuclear charge increases

force of attraction between nucleus and outer electron increases

negligible increase in shielding as each successive electrons enters the same energy level

so more energy is needed to remove the outer electron

State element in P3 that has higher first ie

argon

Describe trend in electronegativity as you go across P3

nuclear charge increases

atomic radius decreases

more electrons but increase in shielding is negligible as each extra electron enters the same energy level

so bonding electrons are more attracted to the nucleus

Q: Explain why the melting point of aluminium is higher than the melting point of sodium

aluminium has a greater charge (+3 vs +1) and is smaller so it has greater EFA between delocalised electrons and lattice of ions which requires more energy to break

Describe mp and bp of silicon (3)

high as atoms are held together by many strong covalent bonds in a giant covalent structure.

a lot of energy is needed to break these bonds

Describe structure of phosphorus, sulfur and argon

molecular

strong covalent bonds between atoms

low mp bp due to weak van Der Waals forces between molecules

what does phosphorous exist as?

p4

what does sulfur exist as?

s8

Why does sulfur have a higher melting point than phosphorous?

more electrons and is bigger so it has stronger van Der Waals forces between the molecules so more energy is needed to overcome them

Q: Why is the melting point of silicon much greater than the melting point of sulfur?

silicon has a giant coolant structure and sulfur has a molecular structure

more energy is needed to break the many strong covalent bonds between atoms of silicon than is needed to break the van Der Waals forces between the sulfur molecules