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In helium nucleus there are:

  1. 2 positron, 2 neutrons
  2. 2 protons, 2 neutrons
  3. 2 protons, 2 neutrons, 2 electrons
  4. 2 protons, 2 electrons

Answer (Detailed Solution Below)

Option 2 : 2 protons, 2 neutrons
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Detailed Solution

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CONCEPT:

In an atom's notation, ZXA ; z is an atomic number and A is the mass number.

No. of protons Z 

No of neutrons = A - Z 

EXPLANATION:

The helium atom is presented by 2He4

Z = 2 and A = 4

No. of protons Z = 2

No of neutrons = A - Z = 2

So the correct answer is option 2.

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