Answer:
All elements in the same A group will have the same number of
valence electrons.
Explanation:
Group A has 1 valence electrons.
This question is incomplete. Luckily, I found the same problem which is shown in the attached picture. To answer the question, we must know how the size and charge affect the lattice energy. The answer is: lattice energy increases with the increasing charge of the ions, and decreasing radius of the atoms.
<em>Therefore, the ranking would be: A < B < C</em>.
Control rods are used<span> in </span>nuclear<span> reactors to </span>control<span> the fission rate of uranium and plutonium. They are composed of chemical elements such as boron, silver, indium and cadmium that are capable of absorbing many neutrons without themselves fissioning.</span>
Answer: The missing coefficient is 2.
Explanation:
According to the law of conservation of mass, mass can neither be created nor be destroyed. Thus the mass of products has to be equal to the mass of reactants. The number of atoms of each element has to be same on reactant and product side. Thus chemical equations are balanced.

As in the products, there are 2 atoms of sodium, thus there will be 2 atoms of of sodium in the reactant as well. This will balance the number of hydrogen and oxygen atoms as well.
Thus the missing coefficient is 2.