What is the position of an element in the periodic table if its electron configuration is 1s2 2s2 2p6 3s2 3p5? it's a group 5a element. it's a group 6a element. it's a group 3a element. it's a group 7a element.

If you look at the configuration, you can see that there are less than 18 electrons (count the last numbers).  In fact, there is one less than 18: 17.  Because 18 is Argon, a noble gas, you can see that you have an element from the 17th group, or Group 7A.