The charge of a nucleus is positive because protons are found inside the nucleus while electrons are on shells outside of it. there are three terms because of the different locations of the electrons and what they do. ex. shielding electrons shield the valence electrons from the strong pull of the nucleus
A and D
Density is mass over volume, if mass decreases or volume increases density decreases
Atomic number is same number as the protons...
Neutrons = Mass number - Atomic number ( protons)
Electrons are same number as protons unless the element has a charge..
If it has a charge of +2 it means that the element has 2 less electrons than the neutral atom. If it has a charge of -2 it means that the element has 2 more electrons than what it is supposed to..
