Talk:Atomic number

"A chemical element is uniquely identified by its nuclear charge eZ"--I had two years of chemistry in high school, over 20 years ago, so FWIW, this doesn't make any sense to me. It seems to me that "atomic number" is a very basic sort of topic, in which phrases like "its nuclear charge eZ" should be explained, not assumed. Or am I wrong? --Larry Sanger 23:10, 11 June 2008 (CDT)

I don't see your problem (perhaps because I don't know what FWIW stands for) and therefore it is difficult for me to clarify my text. Maybe the following remarks are helpful.

1. The concept of atomic number predates by a century the discovery of the structure of atoms. In the first half of the 19th century it was discovered that the chemical elements can be characterized uniquely by non-negative natural numbers, always denoted by Z. For instance, the element carbon is characterized by Z = 6 and the element phosphorus by Z = 15. For obvious reasons Z was called the atomic number.

2. In 1911 it was discovered by Ernest Rutherford that an atom has a kind of solar structure, something like planets orbiting the sun. The atom consists of a positively charged particle -- for which Rutherford invented the name "nucleus" (the sun) -- and Z negatively charged particles (the planets). The latter particles were already known in 1911 and had been named electrons. The charge of the nucleus turned out to be the century old atomic number Z (times the elementary charge e). It was speculated and soon proved that the charge of the atomic nucleus was caused by the fact that it contains exactly Z positive particles, each of charge e. These positive particles are called protons.

3. Summarizing the above: an atomic nucleus has charge Ze and this charge characterizes uniquely a chemical element. Thus, the carbon nucleus has charge 6e (contains 6 protons) and the phosphorus nucleus contains 15 protons and hence has charge 15e.

As a final remark, I think that it is very good that a non-scientist (in Dutch called an "alpha"; this is not derogatory, people are proud to call themselves typical "alphas") tries to understand a text written by a typical "beta" (beta is slightly derogatory, for the "betas" are the insensitive people that exploit the earth, causing pollution and global warming while doing this.) --Paul Wormer 04:27, 12 June 2008 (CDT)