What is the common valency of hydrogen in most compounds?

The common valency of hydrogen in most compounds is 1. This is because hydrogen has one electron in its outermost shell (1s orbital), and it tends to either lose or gain one electron to achieve a stable electron configuration similar to that of the noble gas helium (He). In most compounds, hydrogen forms one covalent bond with another atom, sharing one electron with it. This is true for many common compounds such as water (H2O), hydrogen chloride (HCl), and methane (CH4). However, it is essential to note that there are exceptions where hydrogen can have a valency other than 1, such as in the case of metal hydrides where hydrogen acts as a hydride ion (H-) with a valency of -1.