Question

Using the word stable, how do you explain why the alkali metals tend to lose 1 valence electron?

Answer 1

The atoms can lose their outermost valence electrons to form a cation. The metal generally forms cation. The stable word means that the atom or ion follows octet rule, meaning it contains 8 electrons in the valence shell.

Complete step by step answer:
In the periodic table almost all the elements are not stable in nature and because of this they can react with other elements to form new products. The term “stable” means that the atom contains 8 electrons in the outermost orbitals. These electrons are known as valence electrons as they part in bond formation with the other atom to form molecules.
The atom loses electrons or gains electrons to form a stable configuration. They lose electrons to form cation and gain electrons to form anion.
The alkali metals contain elements lithium, sodium, potassium, rubidium, caesium and francium. If we see the electronic configuration of all the alkali metal, we see that the outermost orbital contains one electron. So they lose their one electron to form a cation and a stable configuration.
Lithium (Li): $[He]2{s^1}$
Sodium (Na): $[Ne]3{s^1}$
Potassium (K): $[Ar]4{s^1}$
Rubidium (Rb): $[Kr]5{s^1}$
Caesium (Cs): $[Xe]6{s^1}$
Francium (Fr): $[Rn]7{s^1}$

Note:
In the periodic table only group 18 elements are stable in nature, as they cannot react with other elements they are monatomic in nature. These elements are called noble gases or inert gases. You can see that when one electron is removed from the electronic configuration the ion acquires the configuration of the noble gas.