Question

An atom has a total of 18 electrons.

a)What is the principal quantum number of the outermost shell? In detail

b)How many electrons does the outermost shell shell contain? In detail

Answer 1

Electronic configuration of the atom with 18 electrons = 1s²2s²2p⁶3s²3p⁶.

Principal quantum

The principal quantum number, nn, designates the principal electron shell. Because n describes the most probable distance of the electrons from the nucleus, the larger the number n is, the farther the electron is from the nucleus, the larger the size of the orbital, and the larger the atom is. n can be any positive integer starting at 1, as n=1n=1 designates the first principal shell (the innermost shell). The first principal shell is also called the ground state, or lowest energy state. This explains why nn can not be 0 or any negative integer, because there exists no atoms with zero or a negative amount of energy levels/principal shells

Principal quantum number of the outermost shell = n = 3

As you can see from the electronic configuration electrons in the outermost shell is 8