What is the approximate measure of angle r? just making sure if i'm correct! explain

It's actually 46.4°;
Angles in a triangle add up to 180°;
Angle T is 90° (right angle);
This means angle R + angle I  = 90°;
From the picture, we can see that angle R seems to be slightly larger than angle I;
In order for this to be case, angle R must be greater than 45°;
72.5° is incorrect as it would mean angle I would be only 17.5°, which is far slimmer than angle R and it is clear from the image that this is not the case;
Therefore the only other option for R is 46.3°.

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