How many neutrons are in the element beryllium?
An element is defined as atoms with the same number of protons (and thus electrons). Beryllium has 4 protons and 4 electrons. The number of neutrons can be anything and it is still beryllium. At least three isotopes of Beryllium have been identified but there is only one stable naturally occuring isotope – Beryllium 9. If there are 4 protons, there must be 9 – 4 = 5 netrons in this isotope. The other stable isotope is beryllium 10 with a half life of 2,700,000 years and this must have 6 neutrons. This does not occur naturally but is made in atomic reactors. The other identified isotope is Beryllium – 8 which is made in the same way but immediately splits into two helium nuclei.
