Which one of the following pairs are isoelectronic? a) Mn^2+ and Ar b) Zn^2+ and

Question

Which one of the following pairs are isoelectronic? a) Mn^2+ and Ar b) Zn^2+ and Cu^2+ c) Na^+ and K^+ d) Cl^- and S c) K^+ and Cl^- What is the formal charge on the bromine atom of a) +1 b) -1 c) +2 d) -2 e) 0 What is wrong with the following structure? a) More lone pairs need to be drawn in the structure. b) A second period element cannot have more than 8 electrons in its outer shell. c) The structure would result in a less electronegative element having a more positive formal charge. d) A structure could be drawn that would result in fewer nonzero formal charges.

Explanation / Answer

69. Formal Charge = [no.of valence electrons] -[non bonded electrons+no.of bonds]

Valence electrons of Br = 7 (4s24p5)

Non bonded electrons = 4

No.of bonds = 3

Formal Charge = 7-(4+3) = 7-7 = 0 option e.

70.

Carbon has 4 valency.so it can only form max 4 bonds as it has 4 valency to fill to have 8 electrons in its outermost orbital.thus option B is correct here which says a second period element cannot have more than 8 electrons in its outer shell.5 bonds means 5*2=10 electrons which is not possible.

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