Here's why:
* They are both in the same group (Group 1, Alkali Metals) of the periodic table. This means they have the same number of valence electrons (1), which are the electrons involved in chemical bonding.
* Similar reactivity: Both sodium and potassium are highly reactive metals, readily forming cations with a +1 charge. They react violently with water and are strong reducing agents.
* Similar ionization energies: They have similar first ionization energies, meaning it takes a similar amount of energy to remove an electron from each atom.
Note: While lithium (Li) is also an alkali metal, its properties are slightly different due to its smaller size and stronger attraction to its valence electron.
