Define what is meant by the electronegativity of an atom and explain how and why it varies from left to right across a period of the periodic table. Q 3(b) [65 Marks] (i) The diatomic molecule C2 is known to be diamagnetic. Draw a molecular-orbital diagram for C2, clearly labelling the atomic and molecular orbitals, and use it to explain why C2 is diamagnetic. (ii) Give the definition of the bond order of a diatomic molecule and use it to determine the bond order of C2.