If you build an atom using two protons, two neutrons, and two electrons, two electrons what have you built an atom of?

1 Answer
Nov 30, 2016

Well, you have made a helium atom.......


The number of protons is crucial in detemining the identity of the atom (or element). If the atom contains 2 protons, 2 positively charged nuclear particles, then #Z=2#, and the element is helium by definition.

The number of electrons determine if the element is neutral or charged. And since the number of electrons equals the number of proton, this element is uncharged.

Finally, the nucleus may contain various numbers of neutrons, massive #"nucular"# particles of neutral charge. Given different number of neutrons, isotopes of a given element (and therefore given #Z#) may arise. The number of protons and neutrons is superscripted to the left of an elemental symbol.

Here you have a NEUTRAL isotope of helium, which we would represent as #""^4He#, which is almost 100% abundant. Why don't I have to specify #Z#, or the number of electrons?