Which one of the following statements is correct?
- A.The number of electrons in alpha particle is 2.
- B.The coordination number of EDTA is 6.
- C.The charge of beta (β) particle is +2.
- D.Both carbon and silicon form ionic compounds.
Correct answer
Explanation
The correct answer is B. EDTA is a hexadentate ligand: one EDTA ion binds a metal ion through six donor atoms, so it forms complexes with coordination number 6.
EDTA, ethylenediaminetetraacetate, carries two nitrogen atoms and four carboxylate oxygen atoms, and all six can attach to the same metal ion, wrapping around it like a claw. Such ring-forming ligands are called chelating agents. Because the complexes are very stable, EDTA is used to measure water hardness by titrating calcium and magnesium ions, to treat lead poisoning, and to preserve food and cosmetics.
A is wrong because an alpha particle is a helium nucleus with two protons and two neutrons and no electrons, so its charge is +2. C is wrong because a beta particle is a fast electron with charge -1. D is wrong because carbon and silicon, with four valence electrons, share electrons and mostly form covalent compounds, not ionic ones.
Exam tip: alpha = He nucleus, +2, no electrons; beta = electron, -1; gamma = no charge; EDTA = hexadentate (6).
Practice Questions
View allThe potential difference between the terminals of an electrical heating device is 40 V, when it draws a current of 2 A from the source. Which one of the following is the correct value of current drawn by the heating device if the potential is increased to 140 V?
- A.7 A
- B.5 A
- C.4 A
- D.2 A
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- B.2 only
- C.Both 1 and 2
- D.Neither 1 nor 2
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- B.Short-sight defect can be corrected by a converging spectacle lens.
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- C.Refraction
- D.Dispersion
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