There is no single person who is credited with the discovery of Mercury. Mercury is one of the five planets that can be seen in the night sky without using a telescope or binoculars. The planet Mercury has been known since ancient times and was observed for thousands of years by the people of many different cultures.
Answer:
Ions are formed when atoms lose or gain electrons in order to fulfill the octet rule and have full outer valence electron shells. When they lose electrons, they become positively charged and are named cations. When they gain electrons, they are negatively charged and are named anions.
Explanation:
It's called a compound because different elements are held together by a chemical bond.
When a metal reacts with an acid, say HCl, it reacts with the H+ atoms of the acid to produce H2 gas and chloride ions. Since pH is the negative log of H+ concentration, then it would sensibly decrease because it was used up. The metal oxide would form a coating over the metal. However, as the reaction proceeds, the acid corrodes the metal and exposes a purer surface removing the coating. Thus increasing the concentration of H+.