What is the atomic number for helium?

1 Answer
Apr 2, 2016

The nucleus of the helium atom contains 2 massive, positively charged particles. Thus, Z, the atomic number = 2.

Explanation:

Z is simply the number of protons, massive, positively charged particles, present within the nucleus. Z thus defines the identity of the element: Z=1, hydrogen; Z=2, helium; Z=3, lithium;.................Z=80, mercury.

You do not have to remember these numbers, because in every exam you ever sit you should be provided a copy of the Periodic Table, which lists all the elements in order of atomic number. Of course, you still have to be able to use the table.

Given the examples, Z=1, hydrogen; Z=2, helium; Z=3, lithium;.................Z=80, mercury, how many electrons does each neutral element contain? Why?