Which of the following species has
(a) equal numbers of neutrons and electrons;
(b) protons, neutrons, and electrons in the ratio 9: 11: 8;
(c) a number of neutrons equal to the number of protons plus one-half the number of electrons?
24mg2+, 47cr, 60co3+, 35cl-, 124sn2+, 2266th, 90sr petrucci, ralph h.. general chemistry (p. 63). pearson education. kindle edition.

see explanation...

Explanation:

                               Mg⁺²-24                     Co⁺³-60                     Clˉ-35    

Protons (p⁺)                12                                 27                             17              

Neutrons (n⁰)             12                                 33                             18              

Electrons (eˉ)             10                                 24                             18              

                                  (c)                                 (b)                            (a)

                         12/2 : 12/2 : 10/2      27/3 : 33/3 : 24/3        #n⁰ = 18

                             6    :    6   :    5          9  :   11  :   8             #eˉ = 18

it is the most commonly accepted one

substituting a hydrogen atom with a halogen in a hydrocarbon:

- the single bond remains single. a is wrong.

- the bond with hydrogen is as strong as with a halogen. c is wrong

- a hydrocarbon is saturated if there is no double bond. we do not know that so d is wrong.

- carbon will always have four valence electrons. e is wrong.

by elimination, the correct answer is b. the boiling point of the new compound increases.