Indium is located in group 13 of the periodic table. This means that it has three valence electrons. The number of valence electrons is important because it determines how an element will react chemically, particularly in terms of forming bonds with other elements.
In more detail, indium’s electronic configuration is [Kr] 4d10 5s2 5p1, which shows that the electrons in the outermost shell contribute to its chemical properties. Since it has three electrons in its outermost shell (two in the 5s and one in the 5p subshell), this confirms that indium belongs to group 13, where elements typically have three valence electrons.