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An atom of beryllium has 4 protons, 4 electrons, and 5 neutrons. What is its mass number?​

An atom of beryllium has 4 protons, 4 electrons, and 5 neutrons. What is its mass-example-1

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Answer:

D. 9.

Step-by-step explanation:

Mass number of an atom is the sum of the proton number and neutron number. For Be, the protons are 4 and neutrons are 5. So, we get 9 by adding them.

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