Group 2

Group 2 of the periodic table is called the alkaline earth metals.


Group 2 contains the elements:

  • Beryllium , Be
  • Magnesium, Mg
  • Calcium, Ca
  • Strontium, Sr
  • Barium, Ba
  • Radium, Ra

Properties

The members of group 2 have two valence electrons. They behave similarly to the alkali metals, based on the fact that they will donate two electrons (instead of one) to reach a noble gas shell. It is harder to donate two electrons at the same time compared to one, which makes the alkaline earth metals of group 2 not react as easily as the alkali metals of group 1.

Reactions

The alkaline earth metals do not react with as many substances as the alkali metals do. They take part of approximately the same reactions, but react much more slowly (if at all).

Just as the alkali metals, they react with halogens:

\(\mathrm{Mg(s) + Cl_2(g) \longrightarrow \:MgCl_2(s)}\)

They also react with water:

\(\mathrm{Ca(s) + 2H2O(l) \longrightarrow \:CaOH_2(aq) + H_2(g)}\)

A higher water temperature is required for the reaction to take place. The reactions are not as fast or explosive as of the alkali metals. To compare, we can look at the reaction between calcium and water, and the reaction between potassium and water. These are just side by side in the periodic system. The reaction of calcium is much slower, and doesn't generate enough heat to ignite the hydrogen gas.

If we expose the alkaline earth metals to air, a protective layer of oxide is created, which prevents further oxygen from penetrating the metal, thus stopping the process of rusting:

\(\mathrm{2Ca(s) + O_2(g) \longrightarrow \:2CaO(s)}\)

Abundance in nature

Magnesium ions, calcium ions, and strontium ions are common in nature. Beryllium and radium is not commonly present.

Magnesium ions are needed for the function of or enzymes, and is also used in chlorophyll, which is an important component of the plant photosynthesis. Calcium ions are needed to build our skeleton, and is used as a signal substance in our cells.

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