S-block

The s-block is one of the four large sections of the periodic table of elements. It is classified according to the type of orbital (electron region) into which its outermost electrons enter. In s-block elements, the outermost electron enters an s orbital of the outermost shell.

An s orbital can hold at most two electrons. Therefore the s-block contains only two groups: group 1 and group 2. Hydrogen and helium are also commonly included, though both have chemical properties distinct from the other elements in their respective groups.

Elements present

Group 1 is called the alkali metals: lithium, sodium, potassium, rubidium, cesium, and francium. Group 2 consists of the alkaline earth metals: beryllium, magnesium, calcium, strontium, barium, and radium. Hydrogen and helium are gases, not metals.

Chemical properties

S-block metals have low ionization energy, meaning electrons are easily removed from them, making them highly reactive. Group 1 elements form ions with a charge of +1, while group 2 elements form ions with a charge of +2. Their reaction with water produces hydrogen gas and an alkaline solution, particularly in group 1.

As one descends a group, atomic size increases and ionization energy decreases. Consequently, reactivity increases further down. Because of their high reactivity, these elements do not occur in nature in their pure form; they are found only in compounds and minerals.

Uses and significance

Sodium and potassium play important roles in the functioning of living cells, including the transmission of nerve signals. Calcium is a component of bone. Lithium is used in rechargeable batteries, and magnesium is employed in lightweight alloys.