What are radioactive tracers used for

Radioactive tracers are widely used to diagnose industrial reactors, for instance by measuring the flow rate of liquids, gases and solids.

Explanation:

Radioactive tracers are widely used to diagnose industrial reactors, for instance by measuring the flow rate of liquids, gases and solids. A radioactive tracer is a chemical compound in which one or more atoms have been replaced by a radioisotope.

heres the link for more information

https://www.iaea.org/topics/radiotracers#:~:text=Radioactive%20tracers%20are%20widely%20used,been%20replaced%20by%20a%20radioisotope

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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.