1) Explain what is meant by exceptional stability of an atom? Why are some elements like copper are exceptionally stable?
2) How can you say that when there is a positive sign on any element, it looses an electon and when there is negative sign on any element, it gains an electron?
Copper,silver and goldhave a single outer electron. This seems disadvantageous, energy-wise, until you look at the orbitals the electrons are in. The lone electron is in an S-orbital. This orbital is thushalf full(since s-orbitals can contain 2 electrons), whereas all the other orbitals in copper, silver and gold are filled, and hence exceptionally stable. After a full orbital, the next most stable orbital is a half full one.
Take copper, for example. If it followed the arrow diagram, it would have the outer orbitals 4s2 3d9, with a full orbital, and an orbital that is neither full nor half full. Copper actually has 4s1 3d10, a half full orbital and a full one, which provides higher stability to the atoms.
ans 2)
when there is a positive sign on any element, it looses an electon and when there is negative sign on any element, it gains an electron
you can also understand it by a example like
when you take loan from bank you are taking money from them and you have to repay them just like this take in electron case when you give electron to some one you are in good condition (+) and whenever you take electron from someone you are in debt means you have to give it like in bank case so you are not in good case so electron become (-)ve
hopes it works for you coz it works with me