2.1.2 Physical Properties of Period 3 Elements
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Explain why phosphorus has a lower melting point than sulphur.
• phosphorus exists as P₄ whilst sulphur exists as S₈ • sulphur is bigger than phosphorus (more electrons) • sulphur has stronger Van Der Waals forces • so more energy is required to break the intermolecular forces of sulphur
State & explain the general trend in first ionisation energy across period 3.
generally increases as across the period: → increasing nuclear charge → similar shielding → stronger attraction between outer e- & nuclues → more energy required to overcome
Why is the 1st ionisation energy of aluminium less than that of magnesium?
• the Al electron is in a 3p orbital • the Mg electron is in 3s orbital • 3p has a higher energy than 3s
Why is the 1st ionisation energy of krypton greater than that of bromine?
• Krypton has more protons • its outer electrons are in the same shell • stronger attraction between e- & nucleus • requires more energy
Explain why the 1st ionisation energy of sulfur is less than that of phosphurus.
• in sulfur, the electrons start pair up in 3p orbital • this causes repulsion • therefore requires less energy to remove the e-
State & explain the general trend in atomic radius energy across period 3.
increases across the period: → increasing nuclear charge → similar shielding → stronger attraction between outer e- & nucleus → (shells are pulled in more)
State & explain the general trend in conductivity across period 3.
decreases across the period: → Na-Al are metals → Si-Ar are non-metals → non-metals cannot conduct electricity as they have no free electrons