If the first two orbits of an atom are completely filled with electrons and no electron is there in the third shell, then the atomic number of the element is ________.
A
10
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B
2
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C
18
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D
32
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Solution
The correct option is A 10 The maximum number of electrons that a shell can accommodate is given by 2n2.
The table given below shows the maximum number of electrons present in the first three shells:ShellShell number, nMaximum number of electronsK 12L28M318 - As the first two shells are completely filled, the number of electrons present in the element is 10.
- The atomic number of a neutral element = number of protons = number of electrons present in the orbits.
- Hence, the atomic number of the element is 10.