The governing body shall elect the number of directors provided in the certificate of incorporation of the corporation for staggered terms of office. At the time of the election of the first board, the governing body shall divide the directors into three groups containing as nearly equal whole numbers as may be possible. The first term of the directors included in the first group shall be two years; the first term of the directors included in the second group shall be four years; the first term of the directors included in the third group shall be six years; and, thereafter, the terms of all directors shall be six years; provided, that if at the expiration of any term of office of any director a successor shall not have been elected, then the director whose term of office shall have expired shall continue to hold office until his successor shall be so elected.