A) ambos pertencem ao 5o período da Tabela Periódica; b) X é um metal de transição interna;
c) Y é um metal de transição externa;
d) ambos possuem, respectivamente, números atômicos iguais a 38 e 40;
e) X pertence à família 2 e Y, à família 4 da Tabela Periódica.

A

Explanation:

n+h→nh3

we must remember that nitrogen and hydrogen are both diatomic molecules in their standard gas form. this adjusts the equation to

n2+h2→nh3

now we need to adjust coefficients in order to balance the atoms on each side of the equation. currently we have 2 atoms of nitrogen and 2 atoms of hydrogen on the reactant side and 1 atom of nitrogen and 3 atoms of hydrogen on the product side.

we can balance the hydrogens by placing a coefficient of 2 in front of ammonia and a coefficient of 3 in front of the hydrogen.

n2+3h2→2nh3

this gives us 6 hydrogen on each side and coincidentally the nitrogens now equal 2 on each side.