Which one of the following is a balanced equation?
o a. 2nh3 (g) + 3mg (s) - 3h2 (g) + mg3n2 (s)
ob. 4nh3 (9) + mg(s)* - h2(g) + mg3n2 (s)
oc. nh3 (9) + mg (s) - h2 (9) + mg3n2 (s)
o d. ca (s) + 02 (9) - 2cao (s)

OA is a balanced equation.

Explanation: For an equation to be balanced, the number of atoms and the total charge of each element in the reaction, of the product and reactant side must be the same.

Considering OA; 6 atoms of nitrogen is present in the reactant side. Shifting to the product side, 6 atoms of nitrogen is also present. Taking the other element in the reaction into account, the number of atoms of each element balances on both sides.

since the atomic number is the number of protons in the nucleus, as we move to the left on the periodic table, the electrostatic pull between the nucleus and the valence electron shell decreases. as we move down a group (vertical column), the valence shell energy level gets further and further from the nucleus.