I've been really struggling with these. can someone assist with this?

When dealing with little odds you must know one part and the whole part. For number 1 a fraction , 7 is a part of a 11 which is the whole. For 2 a percent, 6% part and 100% whole, here you had to know that for 6% to exist there had to be a 100% . For 3 a ratio, the first number is part (2) and the second is whole (7). Look at pic for all work.

Element 17 is chlorine it is a group 7 element(halogen) and belongs to period 3 of the periodic table

Iagree that is the answer to the question