Lithium is the third element in the periodic table, and it belongs to Group 1, which is also known as the alkali metals. Being in this group means that lithium has one electron in its outermost shell. This outer electron is what we refer to as a valence electron.
Li (Lithium), with an atomic number of 3, has the electron configuration of 1s² 2s¹. The ‘2s¹’ indicates that there is one electron in the second shell, and since it is in Group 1, we can conclude that the number of valence electrons for lithium is 1.