Create a rule about how many valence electrons an atom will have

Most of the elements have their 8 electrons in its outermost shell this shell is called valence shell.

The most of elements containg 8 electrons to their valence shell are mostly stable in nature and rule obey octet rule the is 3n subshell surrounds 18 electrons.

e. g Nobel gases shows octet rules.

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.