What type of bond does HCl form?
"Hydrogen has +1 valency and chlorine has -1 valency. So, they share a single electron and form a single covalent bond between them. "
Chlorine is -1, meaning it has one extra electron. Hydrogen is +1, meaning it requires one electron to fill its valence (if only) shell. therefore HCl is an ionic bond where hydrogen is stealing one electron from chlorine.
If Hydrogen gas is chemically combined with Chlorine gas, Hydrogen chloride is formed: H2 (g) + Cl2 (g) ---> 2 HCl (g) The bond is covalent (the atoms share electrons) and polar (Chlorine is more electronegative). Hydrogen chloride gas will dissolve in water and disassociate into ions: HCl ---> H+ (aq) + Cl- (aq)