A centrifuge was used to separate a sample into its components. What conclusion about the sample can be formed based on the technique used? ( not heterogenous) It was a pure substance.
It was a compound.
It was a homogeneous mixture

answer; i believe that the correct answer is (a); a large rock being weathered by wind and rain;

i believe it is-

d.) gravity pulled particles of dust and gas together to form planets.

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.