A proton weighs 1.007276 amu , a neutron weighs 1.008665 amu, and an electron weighs 5.486×10−4 amu. What is the expected mass of a beryllium-9 nucleus, based on the total mass of its protons and neutrons?

1 Answer
Jun 12, 2016

Answer:

This question is similar to "you buy 5 lemons at $0.33 each and 5 oranges at $0.45 each. How much change do you have from $5-00 ?#

Explanation:

You have a #""^9Be# atom, #Z=5#. There are 5 protons, and 4 neutrons, and 5 electrons. Why?

#"Mass"# #=# #(5xx1.007276+4xx1.008665+5xx5.486xx10^-4)" amu"# #=# #??" amu"#.

The mass of the electron is probably insignificant with respect to the mass of the nuclides. It would not be with respect to the binding energy, which I suppose is the next question.

You might have got a quicker and more sophisticated answer in the physics forum.