Chemical reactions chemical equilibrium occurs when the rates of the reactions
a. equal out in both directions.
b. increase from reactant to product.
c. increase from product to reactant.
d. decrease from reactant to produ

the density(ratio between mass and volume as m/v) decreases from top to bottom in periodic table group as the size increases and nuclear charge decreases. but in periods density increases from left to right as atom size decreases and nuclear charge increases.

1. a)c-14 has two more protons

2. d)they have different numbers of protons, neutrons, and valence electrons; they are all gases at room temperature.

3. c) iron and nickel.