Beryllium has a nucleus composed of protons and neutrons. given the data, how many neutrons are in a typical beryllium nucleus?

The molar mass of an element mostly consists of the protons and neutrons (electrons are a few thousand times lighter).  The atomic number of of Be is 4, meaning it has 4 protons (# of protons is what defines an element, change that, change the element).  Since it has 4 protons and its weight is around 9, there are then typically 9-4= 5 neutrons.  The fact that the weight is actually 4.012182 means that in a large sample there are a small percentage of other isotopes.

It won't lose or gain electrons if it's a covalent bond it shares the electrons with another atom or atoms. if it is an ionic bond it will lose the 3 electrons on the outer shell and become a positively charged ion.  credit goes to @sunshinebaby of answers.yahoo.com.