What are the protons, neutrons, and electrons for a sulfur(2-) anion with a mass number of 33?

1 Answer
anor277
Dec 11, 2016

Well, number of protons is easy. It's #"sulfur, Z = 16",# so there are 16 #"nucular protons"#.

Explanation:

If there are 16 positively charged particles, there must be 16 negatively charged particles in the #"neutral"# element. We have #S^(2-)#, and thus there must be #18# electrons associated with the ion.

And neutrons for #""^33S#? Well, the electrons are along for the ride, and have zero rest mass. The mass of an atom, to a first approximation, is the number of massive, nuclear particles, i.e. the number of #"protons and neutrons"#. We have #16# nuclear protons, so there MUST BE #17# #"neutrons"#, i.e.

#33_("the mass number")=16_("protons")+17_("neutrons")#.

Are you happy with this? If you think it is simple, it should be, but many students are unconvinced by this apparent simplcity.

From where did I get these numbers?

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