What si unit is used to measure the number of representative particles in a substance? a. kilogram b. ampere c. kelvin d. mole

D. Mole

Explanation: A unit is defined as the standard of reference chosen to measure  any physical quantity.

A. Kilogram is the S.I unit of mass.

B. Ampere is the S.I unit of electric current

C. Kelvin is the S.I unit of temperature.

D. Mole is the S.I unit of mole of a substance. A mole is the amount of substance which contains as any elementary entities as there are atoms in 0.012 kg of carbon-12.

yes it is balanced

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.