Answer:
Column 17 halogens
Explanation:
To answer the question we need to know the following;
What are valence electrons?
- Valence electrons are outermost electrons in the outermost energy level of an atom of any element.
What are halogens?
- Halogens are group 7 elements that have seven valence electrons. They include, chlorine, fluorine, iodine, etc
What is the reactivity of halogens?
- Halogens are the most reactive non-metals in the periodic table. They react by gaining one electron to attain a stable configuration.
Endothermic reactions are reactions that require heat in the course of the process. The heat of reaction in this case is positive which means the energy of the products is greater than the energy of the reactants. In this case, the answer to this problem would have to be <span>1. must be greater than the required ΔH </span>
Answer:
smallest is O then Se then K then Cs.
Explanation:
These trends exist. elements tend to get smaller as it completes it's shell since there is more attraction when it is complete. plus the further down the periodic table you go the bigger it is. there are more electrons which repulse each other and make it bigger.
Hmm, I am not quite sure but if I am probably your best bet so I'd go with, either B or D.
