What is changes in a chemical reaction

The chemical reaction produces a new substance with new and different physical and chemical properties. Matter is never destroyed or created in Chemical reactions. The particles of one substance are rearranged to from a new substance. The same number of particles that exist before the reaction exist after the reaction

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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.

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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.