The phase change in which a substance changes from a solid to a liquid is
a. freezing.
b. melting.
c. sublimation.
d. condensation.

well off of my head we know that the perfume bottle is most likely opened, or broken. i can also tell it is moving at low and high concentration because it is covering the other side of the room. what we can obtain from this information is it explains why the odor can be detected at the other side of the room.

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.