A hydrogen atom has 1 valence electron. Valence electrons are the electrons in the outermost shell of an atom, and they play a crucial role in chemical bonding and reactions.
Hydrogen is the first element in the periodic table, with an atomic number of 1. This means it has only one electron in its single electron shell. Since this electron is in the outermost shell, it is considered a valence electron.
Understanding the number of valence electrons in an atom is essential for predicting how it will interact with other atoms. In the case of hydrogen, its single valence electron allows it to form bonds with other elements, such as oxygen in water (H2O) or carbon in hydrocarbons.