INORGANIC CHEM - PERIODICITY Flashcards
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
