21. With 20 valence electrons , nickelocene has the highest electron count of the transition metal metallocenes. 22. With only three valence electrons per boron atom, simple covalent bonding cannot fulfil the octet rule. 23. During most molecular bonding, it is the valence electrons which principally take part in the bonding. 24. This form of iron is very stable structurally because it's valence electron shell is half filled. 25. In ionic compounds, beryllium loses its two valence electrons to form the cation, Be 2 +. 26. A thorium atom has 90 protons and therefore 90 electrons, of which four are valence electrons . 27. The noble gases have full valence electron shells. 28. The typical elemental semiconductors are silicon and germanium, each atom of which has four valence electrons . 29. Acceptor impurity atoms have fewer valence electrons than the atoms they replace in the intrinsic semiconductor lattice. 30. So which one is the valence electrons ?
