The atomic mass of the^4He atom is 4.002603 u. How many protons, neutrons, and e

Question

The atomic mass of the^4He atom is 4.002603 u. How many protons, neutrons, and electrons does this (neutral) one atom of helium have? What are the atomic number and mass number? What is the ground state configuration of its electrons, what quantum numbers n and I do they have, and name an allowed transition for one of the electrons if alone. Find the binding energy of the^4He nucleus. Consider^3He instead, which is radioactive (a beta emitter). What real function (it also describes quantum-tunneling wavefunctions) describes the number of atoms that remain as a function of time?

Explanation / Answer

a)

number of protons = 2

number of neutrons = 4 - 2 = 2

number of electrons = 2

b)

atomic number = 2

mass number = 4

c)

electron configuration : He - 1s2

quantum numbers :

n = 1

l = 0

d)

mass of protons = 2 x 1.0073 = 2.0146

mass of neutrons = 2 x 1.0087 = 2.0174

mass of He = 2.0146 + 2.0174 = 4.032

mass defect = actual - calculated

= 4.002603 - 4.032

= 0.029397 amu

binding energy = mass defect x 931.5

= 0.029397 x 931.5

= 27.38 MeV

binding energy per nucleon = 27.38 / 4 = 6.85 MeV

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