2(a) Group 1 (Alkali metals)

what are the group 1 metals?

lithium, sodium, potassium, rubidium, caesium, francium

properties of the group 1 metals (4)

how do they change as you go down the group?

soft - can be cut with a knife, get softer as you go down the group

relatively low densities - first 3 are less dense than water, they get denser as you move down the group

low melting points - decrease as you move down the group due to decreasing attractive forces between outer electrons and positive ions because as more electron shells are added, the electrons get further away from the nucleus

very reactive - only need to lose 1 electron to become stable

what type of ions do the group 1 metals form?

1+ ions

how does reactivity change in the group?

reactivity increases as you go down the group

explain the reactivity trend in the group 1 metals

as you go down the group, more electron shells are added

this means that the outer shell electron gets further away from the nucleus

the electrostatic forces of attraction are therefore weaker, meaning that the outer shell electron can be lost more easily

the alkali metals therefore get more reactive as you go down the group

what do the group 1 metals form when they react in water?

alkalis

what is the formula for group 1 metals reacting with water?

what is the equation for group 1 metals reacting with water?

Group 1 metal + water → metal hydroxide + hydrogen

2M_(s) + 2H₂O_(l) → 2MOH_(aq) + H_2(g)

(where M is Li, Na, K, Rb or Cs)

they form alkalis in water

what observations are made when group 1 metals react with water, and how do they change? (4)

fizzing/effervescence that intensifies

metal moves on the surface of the water with increasing speed

the metals dissolve faster

potassium burns with a lilac flame

what do the group 1 metals form when they react with air?

metal oxides

they tarnish in air

what is the formula for group 1 metals reacting with air?

group 1 metal + oxygen → metal oxide

4M_(s) + O_2(g) → 2M₂O_(s)