# Which quantum number determines the radius of an atom?

The principal quantum number(n) signifies the distance from the nucleus and the size of an atom.

## Principal quantum numbers

• Principal quantum numbers are denoted by the symbol ‘n’.
• They designate the principal electron shell of the atom.
• Since the most probable distance between the nucleus and the electrons is described by it, a larger value of the principal quantum number implies a greater distance between the electron and the nucleus.
• The value of the principal quantum number can be any integer with a positive value that is equal to or greater than one.
• The value n=1 denotes the innermost electron shell of an atom, which corresponds to the lowest energy state of an electron.