Question

What do the elements lithium, sodium, and potassium have in common?

Answer 1

Hint : Lithium, sodium, and potassium are all alkali metals. It is the first group of the periodic table and occupies the leftmost side.

Complete Step By Step Answer:
Lithium $(Li)$, sodium $(Na)$ and potassium $(K)$ are part of a group called alkali metals. The other elements of this group are rubidium $(Rb)$, cesium $(Cs)$ and francium $(Fr)$. Francium is a radioactive element and has a very small half-life. All the elements of alkali metals are found in group $1$ of the periodic table. They occupy the leftmost side of the periodic table.
Alkali metals are very reactive metals with potassium being the most reactive of all the elements. They have an electronic configuration of $n{s_1}$. Alkali metals have one electron in their outermost shell and tend to lose one electron to get a valency of $+ 1$. The $+ 1$ valency results in them being the most electropositive elements and due to this reason, they are found in a pure state in nature. They are very soft in their elemental form and react violently with water. The violent reaction of water is due to the fact that they lose an electron to achieve the stable octet of electrons (also called noble gas configuration).
Alkali metals are good reducing agents with lithium being the strongest reducing agent among all the elements. The reducing character decreases on going down from sodium to cesium.
All of them show a characteristic color on heating.

Note :
In some periodic tables, hydrogen is placed just above the alkali metals. However, hydrogen is not considered an alkali metal because it is mostly found as a gas at normal temperature and pressure. Hydrogen can show properties or transform into an alkali metal when it is exposed to extremely high pressure.