Answer:
2,7 m
Explanation:
You can solve this doing an energy balance:
![m*g*h-\frac{1}{2} *m*v^{2} =41,7[J]](https://tex.z-dn.net/?f=m%2Ag%2Ah-%5Cfrac%7B1%7D%7B2%7D%20%2Am%2Av%5E%7B2%7D%20%3D41%2C7%5BJ%5D)
Solving this equation to get h:

Replacing the values and solving brings to 2,7 m
That element is manganese. As they are in same horizontal row (period) and are next to each other. That is why they show same properties.
Hope this helps xox :)
<span>Answer:
Correct answers are- Electron affinity decreases; Cl has 7 valence electrons but Na has only 1. So Na is going to lose its e, Cl is going to gain an e.</span>