How are atoms of the same element with different mass numbers called?

Isotopes

Explanation:

Isotopes are the same element with different masses because of the different number of neutrons. Also, the element doesn't change. If we change the protons, the element will change and then it won't be an isotope. Hope it helps!

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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.