The valence electrons of element 12 (Mg) are in the 3s orbital. Valence electrons are the electrons in the outermost energy level (or shell) of an atom. In the case of magnesium, which has an atomic number of 12, the electron configuration is 1s2 2s2 2p6 3s2. This means that magnesium has 2 electrons in its 3s orbital, which is its outermost energy level. The 3s orbital is located in the third energy level (or shell) of the magnesium atom. The 1s and 2s orbitals are located in the first and second energy levels, respectively, and the 2px and 2py orbitals are also located in the second energy level. Valence electrons are important because they are involved in chemical bonding and reactions. In the case of magnesium, having 2 valence electrons in its 3s orbital allows it to form chemical bonds with other atoms by either losing or sharing those electrons. Therefore, the valence electrons of element 12 (Mg) are in the 3s orbital, which is located in the outermost energy level of the atom.