Answer:

1. Atoms of an element with the same mass number make up an isotope of the element

2. Nitrogen has an atomic number of 7 ( Z = 7 ) because it has 7 prestons in it's nucleas.

Some nitrogen atoms have an atomic mass number of 15 ( A = 15).

3. Boron is a chemical element with the symbol B and atomic number 5.

5. 9

Step-by-step explanation:

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