Copper is used instead of gold because gold is way to expensive and not practical.
That would be called the atom itself since it consists of the nucleus and one or more electrons
It's neither since the copper isn't changing at all. Electrons are just flowing through the copper atoms.
To be in a neutral state (which it normally is since it is a noble gas) it must have two electrons spinning around its nucleus.
Strontium. They both have two electrons in their outermost energy level, however since the electrons are farther from the nucleus in Strontium than in Calcium, Strontium is more readily able to shed these two electrons to achieve a more stable state with it's outermost energy level being complete (with 8 electrons).
An ion that has three more protons in the nucleus than there are electrons outside the nucleus will have a charge of +3.
The isotope nitrogen-13 (n-13) has an atomic number of 7, meaning it has 7 protons in its nucleus. Since it is neutral, it also has 7 electrons orbiting the nucleus. Therefore, nitrogen-13 has 7 electrons.
Ruthenium (Ru) has 44 protons and 57 neutrons in its nucleus. Since it is a neutral atom, it also has 44 electrons surrounding the nucleus.
The charge of an atom's nucleus is determined by the number of protons it contains since protons have a positive charge. In this case, with 11 protons, the nucleus has a total charge of +11. Electrons, which are negatively charged, balance this charge, but they are not part of the nucleus. Therefore, the charge of the nucleus remains +11, regardless of the number of electrons present.
Since the electrons are negatively charged and the nucleus is positively charged due to presence of protons, they attracted towards each other by the electrostatic force of attraction and thus electrons keep revolving around the nucleus and do not run away
That's actually not quite how it works, you're probably going by an outdated model of the atom. It is true that the probability of finding the electron at a larger distance from the nucleus tends to be larger for electrons with higher energy... the reason why should be fairly obvious: they have more energy to overcome the electromagnetic attraction between the (negative) electron and the (positive) nucleus.
A single chlorine atom has 17p+ (Protons) and 17e- (Electrons). Chlorine will form a 171- anion by gaining one electron, completing the valence shell as an octet.
Carbon-14 has 6 protons and 8 neutrons in its nucleus, making it an isotope of carbon. Since it is a neutral atom, it also has 6 electrons, which balance the positive charge of the protons in the nucleus.