Estimate: -√82
a. -9, 0
b. -9, 9
c. -9
d. 9

The answer is:  [C]:  " -9 " .


Note:  The square root of a positive number will be a positive number.  The negative value of a positive number will be a negative number only.  That leaves us with "Answer choice:  [C]:  "-9" .    Also, we know that the square root of 81 is "9" ;  so the square root of "82" is close to "9" ;  so the negative value of "-9" would be close to that value;  so among the answer choices given, this value, "-9", makes sense.

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