1. Which statement best describes why a gas is easily compressible while most solids
are incompressible?
A. The molecules of a gas are much smaller
than those of a solid.
B. The molecules of a solid are not attracted to
one another.
C. The molecules of a gas are much further
apart than those of a solid.
D. The molecules of a solid are much larger
than those of a gas.

C) The molecules of a gas are much further

apart than those of a solid.

14,16 18 reacts with group

explanation:

let the different atoms be x and y. each with four protons and same mass will be represented as follows.

mass number is number of protons + number of neutrons.

            and  

since, it is given that one has a negative charge while the other is neutral. therefore, there will be increase in number of protons and the atom will be represented as follows.

according to periodic table, mass number of beryllium is 9 and it has atomic number 4 so, the atoms will be and .  

the protons and neutrons will be located inside the nucleus whereas the electrons will be revolving around the nucleus.