U2S1 periodicity

Question 1

What do atoms in the same period have the same number of

Answer 1

Electron shells

Question 2

What do atoms in the same group have the same of

Answer 2

Electrons in outer shell so therefore have similar properties

Question 3

What happens to atomic radius across a period

Answer 3

• decreases
• positive charge of nucleus increases so electrons pulled closer to nucleus

Question 4

Why does graph of melting point across a period look like it does

Answer 4

• Na, Mg, Al - melting point increases as more delocalised electrons
• Si - macromolecular
• P, S, Cl - molecular substances so depends on van der waals forces

Question 5

What happens to first ionisation energy across a period

Answer 5

• increases
• due to increasing attraction between outer shell electrons and nucleus