Question 6
In a crystal of sodium chloride, how many chloride ions surround each sodium ion?
The right answer is the one marked above.
Six. The ions pack into a three-dimensional lattice in which every sodium ion has six chloride neighbours and every chloride ion has six sodium neighbours.
One is the tempting answer, because the formula is NaCl — but that formula gives a ratio, not a pairing. A charge attracts in every direction at once, so an ion is never bonded to just one partner.