Subject: How can two negatively valent elements combine? eg, ClO2

Elementary chemistry and physics teach us that positively and negatively 
valent elements can combine to form compounds. Completion of electronic shell 
structures are explained as a rational for such compound formations. Then one 
hears about compounds of negatively valent elements such as chlorine dioxide 
that flies in the face of that rational. Can you explain?

Re: How can two negatively valent elements combine? eg, ClO2