GROUP 1 ALKALI METALS
26 January 2021
16:58
Physical properties:
● Low density
● Soft
● Low m.p
Ionisation energy decreases as you go down the group.
● More shielding due to more energy shells.
● Larger atomic radius, so outer electrons further from nucleus
● Therefore weaker electrostatic force of attraction between the outer
electrons and the nucleus.
This also explains the increased reactivity down the group, as its easier to lose the
outer electron down the group.
Ionic radius is smaller than atomic radius as they have lost an electron shell.
● More attraction between nucleus and electrons.
Powerful reducing agents as they give up electrons to form +1 ions.
Reactions with water:
2Li(s) + 2H2O(l) ---> 2LiOH(aq) + H2(g)
● With lithium, reaction is steady, giving steady steam and bubbles of hydrogen.
● With sodium, reaction is slightly violent, it melts forming a shiny bead which
skates around the surface of water.
● With potassium, reaction is very violent, the hydrogen catches fire and the
potassium burns with a lilac flame.
Reactions with chlorine form colourless (white) ionic chlorides.
2M(s) + Cl2(g) ---> 2MCl(s)
● All group 1 metals react violently with chlorine.
GROUP 2 ALKALINE EARTH METALS
, 26 January 2021
19:15
Atomic radius increases down the group, as there's an increasing number of electron
shells.
The ionisation energy decreases as you go down the group.
● Increased shielding.
● Greater distance from outer electron and nucleus.
● Weaker force of attraction
Reactivity increases down the group.
Melting point decreases as you go down the group.
● Ions become bigger and less packed together.
● Increased shielding.
● Increased atomic radius, further distance between nucleus and delocalised
electrons.
● Weaker electrostatic force of attraction, weaker metallic bonds.
REACTIONS OF THE GROUP 2 ELEMENTS
26 January 2021
20:31
Group 2 elements are reducing agents as they readily lose electrons to form 2+ ions.
Reactions with oxygen:
2M(s) + O2(g) ---> 2MO(s)
● Mg, burns very brightly with an intense white flame.
● Ca, burns brightly with a red flame.
● Ba, burns in excess air or oxygen with a green flame, forms a peroxide - BaO2
Group 2 metals form white oxides.
Reactions with water:
M(s) + 2H2O (l) ---> M(OH)2(aq) + H2(g)
● Mg, reacts very slowly with cold water. Much more rapidly on heating in
steam to produce MgO.
● Ca, initially calcium hydroxide dissolves, but solubility is low, solution become
saturated and white precipitate appears.
● Ba, reacts fast and is soluble.
Reactions with chlorine:
M(s) + Cl2(g) ---> MCl2(s)
All form white chlorides.
26 January 2021
16:58
Physical properties:
● Low density
● Soft
● Low m.p
Ionisation energy decreases as you go down the group.
● More shielding due to more energy shells.
● Larger atomic radius, so outer electrons further from nucleus
● Therefore weaker electrostatic force of attraction between the outer
electrons and the nucleus.
This also explains the increased reactivity down the group, as its easier to lose the
outer electron down the group.
Ionic radius is smaller than atomic radius as they have lost an electron shell.
● More attraction between nucleus and electrons.
Powerful reducing agents as they give up electrons to form +1 ions.
Reactions with water:
2Li(s) + 2H2O(l) ---> 2LiOH(aq) + H2(g)
● With lithium, reaction is steady, giving steady steam and bubbles of hydrogen.
● With sodium, reaction is slightly violent, it melts forming a shiny bead which
skates around the surface of water.
● With potassium, reaction is very violent, the hydrogen catches fire and the
potassium burns with a lilac flame.
Reactions with chlorine form colourless (white) ionic chlorides.
2M(s) + Cl2(g) ---> 2MCl(s)
● All group 1 metals react violently with chlorine.
GROUP 2 ALKALINE EARTH METALS
, 26 January 2021
19:15
Atomic radius increases down the group, as there's an increasing number of electron
shells.
The ionisation energy decreases as you go down the group.
● Increased shielding.
● Greater distance from outer electron and nucleus.
● Weaker force of attraction
Reactivity increases down the group.
Melting point decreases as you go down the group.
● Ions become bigger and less packed together.
● Increased shielding.
● Increased atomic radius, further distance between nucleus and delocalised
electrons.
● Weaker electrostatic force of attraction, weaker metallic bonds.
REACTIONS OF THE GROUP 2 ELEMENTS
26 January 2021
20:31
Group 2 elements are reducing agents as they readily lose electrons to form 2+ ions.
Reactions with oxygen:
2M(s) + O2(g) ---> 2MO(s)
● Mg, burns very brightly with an intense white flame.
● Ca, burns brightly with a red flame.
● Ba, burns in excess air or oxygen with a green flame, forms a peroxide - BaO2
Group 2 metals form white oxides.
Reactions with water:
M(s) + 2H2O (l) ---> M(OH)2(aq) + H2(g)
● Mg, reacts very slowly with cold water. Much more rapidly on heating in
steam to produce MgO.
● Ca, initially calcium hydroxide dissolves, but solubility is low, solution become
saturated and white precipitate appears.
● Ba, reacts fast and is soluble.
Reactions with chlorine:
M(s) + Cl2(g) ---> MCl2(s)
All form white chlorides.
