Group 2 Alkaline Earth Metals

Group 2

 The elements in Group 2 are the Alkali Earth Metals. All the elements in this group have 2 electrons on their outer shells. They are in the “s” block. The oxidation state of each of these elements is 2+ because they lose 2 electrons from their outer shells when ionised i.e. their valance electrons are in the ‘s’ orbital.

Group 2 is like group 1 in its trends but it is less reactive.

Trends in Chemical properties

Group 2 elements have an oxidation state of 2+. In compounds too.

General equation for group 2 metals reacting with water:

              M_(s) + H₂O_(l)      à   M(OH)_{2 (aq)}+ H_2(g)

Half equations:  M    à  M²⁺ + 2e^-

                            H₂O + 2e^- à  2OH^- +H₂

Group 2 elements are reducing agents. (donate 2 electrons) – oxidised

 Down group 2 reactivity goes up as there is more shielding to the outer electrons due to the increasing number of shells and therefore an increasing atomic radius and therefore it is easier for them to lose electrons. Because of the increasing number of shells, the pull from the nucleus is weaker.

Magnesium is near the top of the group. It is less reactive due to less shielding and a stronger pull from the nucleus. It won’t react with cold water, but it will react with steam as more energy is provided by the hot steam and activation energy is reached.

The most reactive element in group 2 is radium as it has the largest atomic radius and it requires the least energy to ionise. Because it has the highest number of electrons in the group, it has the highest number of shells and a lot of shielding from the nucleus. This means that during a reaction these 2 electrons are easily lost.

 Trends in Physical properties

Ionisation energy

The first and second ionisation energies decrease as it goes down the group due to the increase in shells and atomic radius. This causes for there to be more shielding and therefore the force of attraction is weaker from the outer electrons to the nucleus. Less energy is required to remove the first and second electron.

 Atomic radius

The atomic radius goes up because more electron shells are added as more electrons are added.

Melting points

The melting points decrease as you go…