Chemistry- Periodicity ❤️

How are elements classified

• In s, p, or d block, according to which orbitals the highest energy electrons are in

Which is period 2 and 3

Period 2- row beginning with Li

Period 3- row beginning with Na

Describe and explain the trend in atomic radius across a period

• Decreases

• Nuclear charge increases across the period

• Shielding is similar as the no of energy levels is the same

• The attraction between the nucleus and outer shell is increasing therefore attracting it closer

Describe and explain the trend in first ionisation energy

• general increase across the period

  • Nuclear charge is increasing

  • Shielding remains similar

  • Atomic radius is decreasing

  • Therefore the electron is more strongly atttracted to the nucleus

Trend in melting and boiling points across period 3 and period 2

Na to Al- metallic bonding- number of delocalised electrons increases per atom increases & ionic radius decreases increasing nuclear charge and increasing charge density

Sillicon- macromolecular- strong covalent bonds between atoms which require a lot of energy to overcome

P to Cl- simple molecular: weak vdw forces between molecules so little energy is needed to break them- low mp and bp

Sulfur (S8) has a higher melting pointt than phosphorus (P4) as it has more electrons so has stronger vdw forces between molecules

Ar is monoatomic- weak vdw forces between atoms