Explanation:
Below is an attachment containing the solution.
A vaccum unlike sound,light can travel through any matter including a great vacuum of nothing (space)
<span>Velocity, you divide distance/time </span>
Answer:
a)The approximate radius of the nucleus of this atom is 4.656 fermi.
b) The electrostatic force of repulsion between two protons on opposite sides of the diameter of the nucleus is 2.6527
Explanation:

= Constant for all nuclei
r = Radius of the nucleus
A = Number of nucleons
a) Given atomic number of an element = 25
Atomic mass or nucleon number = 52


The approximate radius of the nucleus of this atom is 4.656 fermi.
b) 
k=
= Coulombs constant
= charges kept at distance 'a' from each other
F = electrostatic force between charges


Force of repulsion between two protons on opposite sides of the diameter



The electrostatic force of repulsion between two protons on opposite sides of the diameter of the nucleus is 2.6527
answer:They are too close to the sun!
Explanation:Because Mercury is so close to the Sun and its gravity, it wouldn't be able to hold on to its own moon. Any moon would most likely crash into Mercury or maybe go into orbit around the Sun and eventually get pulled into it.Same with Venus!