Someone me with these two. i'll give you brainliest and 25 mathematicians out there

Hello LovingAngel!

To find the slope, you can use the formulas  as well as . I am using the latter to calculate and ensuring my answer with the former. 

[Note: (x,y) is the format for ordered pairs]

First pair:  value 1:(1,5) and value 2:(2,8) 
-> ->  or 3. 

The slope for (1,5) and (2,8) is 3(/1). 

Second pair: value 1: (3,1) value 2 (3,-1)

->  -> 
Slope for the second pair is -2/0

Checking work with 
1. Slope: 3/1, meaning rise (y) +3 and run (x) +1.  (1,5) -> (1+1,5 + 3) -> (2,8) ✔
2. Slope: -2/0, meaning rise (y) -2/drop (y) 2 and run 0. (3,1) -> (3 + 0, 1 + -2) -> (3,-1) ✔

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