What is the difference between a mixture, compound, element and pure substance

mixture = when two or more substances combine without making a new substance.

compound = elements that are bonded together chemically

element = the simplest form of matter that cannot be broken down

pure substance = a substance made up of one compound

basically the differences are their definitions :D

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.