Determine si son ciertas o falsas estas afirmaciones; si al- guna es falsa, corríjala de modo que sea verdad: (a) el nú-
cleo tiene la mayor parte de la masa y ocupa la mayor
parte del volumen de un átomo; (b) todos los átomos de
un elemento dado tienen el mismo número de protones;
(c) el número de electrones de un átomo es igual al núme-
ro de neutrones de ese átomo; (d) los protones del núcleo
del átomo de helio se mantienen unidos por una fuerza
llamada fuerza nuclear fuerte.

a is the correct answer

hydrocarbons are organic compounds that contain only hydrogens and carbons. they can be saturated (those which contain only carbon-carbon single bonds) or unsaturated (those which contain carbon-carbon double or triple bonds) in nature. hydrocarbons can undergo several reactions like substitution, elimination etc.  

on substituting one or more hydrogen atoms in hydrocarbon it results in the formation of haloalkane. as the halogen atoms are large compared to the carbon and hydrogen atoms, due to which the molecular weight increases and the bond become polar because of presence electronegative halogen atom and results in the increase in boiling point of the haloalkane.

thus, the correct option is (b) that is the boiling point of the new compound increases on substituting a hydrogen atom with a halogen in a hydrocarbon.

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.