Lithium, represented as 73Li, has a total of 3 electrons in its neutral state. To determine the valence electrons, we need to look at its electron configuration.
For lithium (Li), the electron configuration is 1s2 2s1. This tells us that lithium has 2 electrons in the first shell and 1 electron in the second shell. The electrons in the outermost shell (the second shell, in this case) are called valence electrons. Therefore, lithium has 1 valence electron.
In terms of group number, lithium is located in Group 1 of the periodic table, which is also known as the alkali metals group. This group contains elements that have similar properties and all have one electron in their outermost shell, making them highly reactive.