Answer:
D is the answer because I think it is right plus I know they don't use two off them
Hydrogen and Helium cannot bond together. Put aside the inertness of helium (or all noble gases), bond formation is only favored when the final state of the two elements is more stable than their initial state. ... Helium compounds has some predictions though none of them contain only those two elements.
Answer:Use an excess of ethane
Explanation:
The halogenation of alkanes is a substitution reaction. All the hydrogen atoms in the alkanes could be potentially substituted. How ever the reaction can be controlled by using an excess of either the alkane or the halogen. If the aim (as it is in this question) is to minimize the yield of halogenated alkanes, an excess of the alkane (in this case, ethane) is used.
The answer is Ra
Atomic number for Be is 4
Atomic number for Mg 12
Atomic number for Ra 88
Atomic number for Ba 56