N shell will have maximum of ________ electrons.
- A.2
- B.8
- C.16
- D.32
Correct answer
Explanation
The correct answer is D, 32. The N shell is the fourth shell (n = 4), and the most electrons a shell can hold is given by the formula 2n², so 2 × 4² = 32. The shells around the nucleus are named K, L, M and N for n = 1, 2, 3 and 4, and the same formula gives them room for 2, 8, 18 and 32 electrons. This is the Bohr–Bury scheme taught in Class 9. One more rule is often tested with it: the outermost shell of an atom cannot hold more than 8 electrons, which is why potassium is written 2, 8, 8, 1 and not 2, 8, 9. A is wrong because 2 is the capacity of the K shell. B is wrong because 8 is the capacity of the L shell. C is wrong because 16 is not the capacity of any shell; the M shell holds 18. Exam tip: remember 2n², so K = 2, L = 8, M = 18 and N = 32.
Practice Questions
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- A.Galileo
- B.Martin Luther
- C.Johannes Kepler
- D.Copernicus
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In 1609 Kepler showed that the planets move around the Sun in elliptical orbits, with the Sun at one focus of the ellipse.
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- C.Urea is produced from digestion of starch.
- D.Urea is produced in lung and kidney.
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- A.Condenser-Objective lens-Eyepiece-Body tube
- B.Objective lens-Condenser-Body tube-Eyepiece
- C.Condenser-Objective lens-Body tube-Eyepiece
- D.Eyepiece-Objective lens-Body tube-Mirror
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- B.Haemoglobin of RBC can carry both oxygen and carbon dioxide.
- C.Haemoglobin of RBC can carry only carbon dioxide.
- D.Haemoglobin is only used for blood clotting and not for carrying gases.
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- B.Histones are proteins that are present in nucleus in association with DNA.
- C.Histones are proteins associated with lipids in the cytosol.
- D.Histones are proteins associated with carbohydrates in the cytosol.
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