Exceptions To The Octet Rule In Chemical Structures

The video explores Lewis structures that deviate from the octet rule, including molecules with incomplete and expanded octets. It explains why certain elements like boron and phosphorus can have fewer or more than eight electrons. Examples such as BH3, PCl5, and ICl5 are discussed, along with molecules like NO and NO2 that have odd numbers of electrons, leading to octet rule violations.

What is the main reason BH3 does not follow the octet rule?

• Hydrogen can only form one bond.

• Boron does not have enough valence electrons.

• Boron can only form two bonds.

• Boron has too many electrons.

Which of the following elements cannot have an expanded octet?

• Chlorine

• Sulfur

• Phosphorus

• Carbon

Why can phosphorus have more than eight electrons in its valence shell?

• It is in the second row of the periodic table.

• It is more electronegative than nitrogen.

• It has access to the 3d sublevel.

• It can form only single bonds.

What is the molecular geometry of PCl5?

• Trigonal planar

• Square pyramidal

• Tetrahedral

• Trigonal bipyramidal

In the molecule ICl5, how many lone pairs are present on the iodine atom?

• None

• One

• Two

• Three

What is a key characteristic of molecules with an odd number of electrons?

• They often violate the octet rule.

• They are always unstable.

• They can never form double bonds.

• They always have a complete octet.

In the case of nitrogen monoxide, which atom is more likely to have a complete octet?

• Neither can have a complete octet

• Nitrogen

• Both have complete octets

• Oxygen

Why does nitrogen dioxide (NO2) violate the octet rule?

• Nitrogen can only form two bonds.

• Oxygen can only form one bond.

• It has an even number of electrons.

• It has an odd number of electrons.

In NO2, which atom is most likely to have an incomplete octet?

• The central nitrogen atom

• The oxygen atom with a double bond

• Both oxygen atoms

• Neither, both have complete octets

What is the total number of valence electrons in NO2?

• 15

• 18

• 16

• 17