INORGANIC CHEM - PERIODICITY
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What is periodicity?
the repeating patterns of atomic, physical, and chemical properties of elements as you move across periods in the periodic table
Describe the trend in atomic radius across a period
decreases
Explain the trend in atomic radius across a period
• no. of protons increases • nuclear charge increases • stronger forces of attraction between nucleus and valence electrons • electrons pulled closer to the nucleus
How do melting and boiling points generally change across a period?
• increase up to group 4 • decrease from group 5
Why do melting and boiling points increase across a period from group 1-3?
• nuclear charge increases • atomic radius decreases • metal ions have stronger charge • stronger electrostatic forces of attraction between +vely charged metal ions and delocalised electrons • stronger metallic bonding • more energy required to overcome forces
Why does silicon have the highest melting and boiling point in period 3?
• giant covalent structure • strong covalent bonds between Si molecules • require lots of energy to overcome
Why do melting and boiling points generally decrease across a period from group 5-8?
• non-metals • simple molecular structure • van der waals forces are weak • require little energy to overcome
Why does P have lower melting and boiling points than S?
• S forms S8 molecules whereas P forms P4 molecules • S8 molecules have more/stronger van der waals forces than P4 molecules
Why does Ar have a very low melting and boiling point?
• noble gases are monatomic • very weak van der waals forces between atoms
Describe the trend in ionisation energy across a period
increases
Explain the trend in ionisation energy across a period
• increased nuclear charge • greater force of attraction between nucleus and outer electron • same amount of shielding