Mendeleev's arrangement of the periodic table was in order of increasing . A. atomic number
B. atomic mass
C. neutron number
D. valence electron number

B. atomic mass

Explanation:

He arranged the elements into rows in order of increasing mass so that elements with similar properties were in the same column.

i believe you are right for all except the 3rd ( look at sqdancefan his answer is much better)

a. energy is absorbed in the reaction.

if in a given reaction the energy of products is greater than the energy of reactants it means that reaction is endothermic and during the reaction, the energy is absorbed by reactants. in an endothermic reaction, the products have more stored chemical energy than the reactants. and in this reaction the reactants are more stable than products before the compounds with less energy are always more stable.