The graph of a logarithmic function is shown below

This represents the function : y = log₆ (x).
Proof:
Rewrite this logarithmic function into an exponential form:

 y = log₆ (x)  ↔ x = 6^y

On the graph we see 2 major points A(1,0) and B(6,1). Plug them in x=6^y
1 = 6⁰ = 1 (true)

6 = 6¹ True, then this confirm that the graph equation is  y = log₆ (x)

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