Question

What periodic trends of reactivity occur with the alkali metals?

Answer 1

In chemistry, reactivity is a measure of how readily a substance undergoes a chemical reaction. All alkali metals have only one electron in their valence shell. Alkali metals tend to lose this electron when they participate in reactions.

Complete answer:
The alkali metals are lithium (Li), sodium (Na), potassium (K), rubidium (Rb), cesium (Cs), and francium (Fr). These elements constitute the first group of the periodic table. All alkali metals have their outermost electron in the s-orbital and thus they correspond to the s-block.
The properties of the alkali metals are similar to each other as expected for elements in the same family. The alkali metals have the largest atomic radii and the lowest first ionization energy in their respective periods.
Although all alkali metals have one valence electron in their valence shell, there are slight differences in the reactivity order of elements on going down the group. As we move down the group, the atomic number and number of shells also increase. The outermost electrons become farther away from the nucleus.
As a result, the shielding effect increases, and the valence electrons are more loosely bound to the nucleus. Thus these valence electrons are now easily available to take part in a reaction and the reactivity of the element is said to be increased.
Hence, the reactivity of alkali metals increases on moving down the group.

Note:
The shielding effect is the effect produced by inner orbital electrons that come and hinder the path of nuclear charge and thus shields the outermost electrons. So, the more the number of inner electrons, the more will be a shielding effect and more easily the outermost electron can escape from the atom.