According to hund's rule, when electrons occupy orbitals of equal energy, one electron enters each orbit until a. there are two electrons in each orbital. b. electron velocities become constant. c. all the orbitals contain one electron, with opposite spins. d. all the orbitals contain one electron, with spins parallel.

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.

answerca air mass;