PLEASE HELP! Chemistry! Can anyone help find me the answer key if there is one? Or explain to me what number of bonding sides around of central atom means? And Coordination # of electron sites around the central atom?

This is what my chemistry teacher had us do.

Explanation:

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.