Which is an example of a covalent bond? there are fewer than 16 valence electrons in 2 chlorine atoms, but they form a stable bond. chlorine accepts 1 electron from calcium to form a stable bond. ions in a bar of pure iron are surrounded by a large number of valence electronsnextreset?

The correct choice should contain the word "share." Electrons are shared in a covalent bond. In an ionic bond, atom(s) take an electron giving it (them) a negative charge and other atom(s) lose an electron giving it them a positive charge.

I happen to know that the chlorine molecule Cl2 is covalent ===> C 

A good answer would have been: 

Water, 2 hydrogen atoms and one oxygen atom SHARE valence electrons.

The activity series is shown in the attached picture. if the element is below the other, then you can displace the other. following the activity series as a guide, the reactions are as follows: nickel and aluminum chloride3 ni + 2 alcl₃  → 3 nicl₂ + 2 albarium and copper bromideba + cubr  →  no reaction because cu is less oxidizable than bapotassium nitrate and aluminum3 kno₃ + al  → al(no₃)₃ + 3 ksodium phosphate and zincnaso₄ + zn  → znso₄ + na