# Student Projects/Problems on atomic number and atomic mass number

**Problems on atomic number and atomic mass number**
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**Introduction**
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An Atom consists of protons, neutrons and electrons. Atomic number is nothing but the total number of protons present on an atom. Atomic mass number is the sum of the total number of protons as well as neutron. So it can be said that mass number is the total number of nucleons. The number of protons is equal to number of electron in neutral atom. The number of neutron is the difference between atomic mass number and atomic number.

**Problems:**
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Compute the number of protons, neutrons and electrons in the given elements.

**a) P (A=31, Z=15)**
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**Given:** Atomic number of Phosphorus = 15, Atomic mass number of Phosphorus= 31. Therefore the number of protons = 15. The number of electrons = 15 (The number of protons = the number of electrons in a neutral atom. The number of neutrons= Atomic mass number – atomic number. I.e. Number of neutrons= A-Z = 31-15 =16. So the number of neutrons = 16

**b) K (A=39, Z=19)**
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**Given:** Atomic number of Potassium= 19, Atomic mass number of Potassium = 39. Therefore the number of protons = 19. The number of electrons = 19 (The number of protons = the number of electrons in a neutral atom. The number of neutrons= Atomic mass number – atomic number. I.e. Number of neutrons= A-Z = 39-19=20. So the number of neutrons = 20.