For Aluminium (Al) (atomic number : 13, mass number: 27), which one among the following statements is NOT correct ?
- A.Number of electrons present in Al is 13
- B.Number of protons present in Al is 13
- C.Number of neutrons present in Al is 14
- D.The valency of Al is 2
Correct answer
Explanation
The correct answer is D, The valency of Al is 2. This is false: aluminium has three electrons in its outer shell and loses all three, so its valency is 3.
The electronic configuration of aluminium is 2, 8, 3. By giving up its three outer electrons it reaches the stable configuration of neon and forms the Al3+ ion, which is why its compounds are written as Al2O3 and AlCl3. Aluminium is the most abundant metal in the Earth's crust and is extracted mainly from bauxite by electrolysis.
A is correct because a neutral atom has as many electrons as protons, and the atomic number 13 gives 13 electrons. B is correct because the atomic number is the number of protons, which is 13. C is correct because neutrons equal the mass number minus the atomic number, 27 - 13 = 14.
Exam tip: protons = atomic number, neutrons = mass number - atomic number; Al is 2, 8, 3 with valency 3.
Practice Questions
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- B.'Scale' found in onion
- C.'Tendril' found in pea
- D.'Hair' present in carrot
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- B.Calcium sulphate
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- D.Calcium phosphate
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- B.ovary and ovule, respectively
- C.ovary, no ovule required
- D.ovule, no ovary required
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After fertilisation the ovary of the flower grows into the fruit, and each ovule inside it develops into a seed.
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