Question

if a +2 ion has 18 electrons, what element is it? argon (ar) calcium (ca) sulfur (s) chlorine (cl)

Explanation:

Step1: Determine the number of electrons in the neutral atom

A +2 ion means the atom has lost 2 electrons. If the ion has 18 electrons, then the neutral atom has \(18 + 2=20\) electrons.

Step2: Relate the number of electrons to the atomic number

In a neutral atom, the number of electrons is equal to the atomic number. So the element has an atomic number of 20.

Answer:

Calcium (Ca)