Hi, brother or sister. me to answer to this question. this two question is most important and me. 1) how does being puncture ( on time) show responsibility? why 2) reliable people can be counted on to do what is expected of them. why is hard to be reliable. i don't those word meaning and that why i am asking you guys to me to answer to question.

b is the correct answer

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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.

            and  

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.