unit 2 section 1 periodicity

Question 1

what is the general trend in melting points across period 3

Answer 1

there is a general increase from sodium(Na) to silicon(si) and then there is a general decrease as you go from silicon(si) to argon(ar)

Question 2

why does the melting point increase from sodium to aluminium

Answer 2

there melting points increase as you go along as the metal-metal bonds become stronger, this is because the metal ions have an increasing positive charge, an increasing number of delocalised electrons and an decreasing radius

Question 3

why does silicon have a high melting point

Answer 3

this is because silicon is macromolecular, with a tetrahedral structure. it contains strong covalent bonds which requires alot of energy to break those covalent bonds.

Question 4

why does the melting point decrease as you go from phosphorus to argon

Answer 4

this is because they are simple covalent molecules and their melting point depends on there weak van der waals forces which are easy to overcome

Question 5

why does sulfur have a higher melting point than phosphorus and chlorine

Answer 5

this is because sulfur is a bigger molecule than chlorine and phosphorus which means it has stronger van der waals forces

sulfur- s8 (largest)
chlorine - Cl2 (middle)
phosphorus - P (smallest)

Question 6

why does argon have the lowest boiling point

Answer 6

this is because argon exists as individual atoms, therefore it has weak van der waals