Why Do Larger Atomic Nuclei Require More Neutrons?

[nathan17]

Radioactivity Justification

1. The problem statements, all variables and given/known data
1a. Justify the appropriate charge and mass number values for an electron, a positron, a neutrino and an antineutrino.

1b. Justify the appropriate charge and mass number values for a gamma ray.

1c. Using the properties of the attractive nuclear force and the repulsive electrostatic force between protons, discuss the reason for the increase in the neutron-to-proton ratio of stable nuclei as the atomic number increase.

Homework Equations

N.A

The Attempt at a Solution

I'm not really sure on how to go about these questions, I am currently on school holidays and the end of year exams keep getting closer and closer so I really want to try get as much work as possible done to ensure that I get a pass in my subjects.

For the first two I think that I am supposed to justify using the laws of conservation (energy, momentum, nucleons, charge (?)) but I don't know how.

For the third question, I'm not sure, but is this correct:
When the mass of the nucleus increases the number of protons increase. Due to this increase, the electrostatic repulsive force increases, this force is long ranged. The addition of neutrons provide an attractive force to increase the spacing between protons, which reduces the average repulsive force per proton

If anyone could shed some light onto this for me, I would greatly appreciate it!

I appologise if I have posted in the wrong section, but seeing how this relates somewhat to coursework (The curriculum statement questions) I figured this would be the best place.

Thankyou,
Nathan

 

[member 553083]

.Answer:1a. Electron: Charge = -1, Mass number = 0; Positron: Charge = +1, Mass number = 0; Neutrino: Charge = 0, Mass number = 0; Antineutrino: Charge = 0, Mass number = 0. These values are determined by the conservation laws of energy, momentum and charge. 1b. Gamma Ray: Charge = 0, Mass number = 0. Gamma rays have no charge and no mass, as they are composed of pure energy and are not particles. 1c. As the atomic number increases, the ratio of neutrons to protons in a nucleus must increase in order to balance the attractive nuclear force and the repulsive electrostatic force between protons. This is necessary in order to achieve a stable nucleus. The addition of neutrons provides an attractive force, which increases the spacing between protons, and thus reduces the average repulsive force per proton.