1.4- Periodicity

Question 0

What is the trend of atomic radii across a period?

Answer 0

Decrease, because the increased number of protons create a more positive charge attraction for electrons which are in the same shell and similar shielding

Question 1

What do s, p, d and f blocks correspond to?

Answer 1

Which orbitals the highest energy electrons are in

Question 2

Trend in melting and boiling points across period 3?

Na, Mg, Al, Si, Cl, S, P, Ar

Answer 2

Na, Mg, Al- Metallic bonding. Strong bonding, gets stronger the more electrons there are in the outer shell that are released to the sea of electrons. A smaller positive centre also makes the bonding stronger. High energy is needed to break the bonds

Si is macromolecular so many strong covalent bonds between atoms and high energy needed to break these covalent bonds so very high melting and boiling points

Cl2, S8 and P4- simple molecular. Weak van der Waals between molecules so little energy needed to break them- low melting and boiling points

S8 has a higher melting point than P4 because it has more electrons so stronger van der Waals

Ar is monoatomic so weak van der Waals between atoms