Final answer:
Elements in the same group of the periodic table have the same number of valence electrons, resulting in similar chemical properties. Based on their relative positions in the periodic table, lithium and sodium would have the same number of valence electrons.
Step-by-step explanation:
Elements in the same column of the periodic table, also known as a group, have the same number of valence electrons. For example, the alkali metal group consists of elements like lithium and sodium, which each have one valence electron. So, based on their relative positions in the periodic table, lithium and sodium would have the same number of valence electrons. The similarity in chemical properties among elements in the same group is due to their shared number of valence electrons.