The four sp$^3$ hybrid orbitals arrange themselves as far apart as possible, forming a tetrahedral geometry.

sp$^3$ hybrid orbitals from each carbon atom

Question 1

Which of the following statements best describes the shape and orientation of an sp$^3$ hybrid orbital as found in methane (CH$_4$)?

Accepted Answer

It is tetrahedral and oriented at 109.5° angles to each other.

Question 2

How many valence electrons does phosphorus have, and how many hydrogen atoms does it bond to in phosphine (PH$_3$) to achieve an octet?

Accepted Answer

Phosphorus has 5 valence electrons and bonds to 3 hydrogens.

Question 3

Which of the following best explains why a carbon-carbon double bond (as in ethylene) is stronger and shorter than a single bond (as in ethane)?

Accepted Answer

A double bond consists of one sigma ($\sigma$) and one pi ($\pi$) bond, increasing electron density between the carbons.

Question 4

Which hybridization and bond angle are found in the carbon atom of formaldehyde (CH$_2$O)?

Accepted Answer

sp$^2$ hybridization, 120°

Question 5

In the context of molecular orbital theory, what is the result of combining two hydrogen 1s atomic orbitals to form H$_2$?

Accepted Answer

One bonding and one antibonding molecular orbital are formed.

Question 6

Which of the following best describes the electron configuration of carbon in its ground state?

Accepted Answer

$1s^2\ 2s^2\ 2p^2$

Question 7

Which statement about the formation of a covalent bond is correct?

Accepted Answer

A covalent bond forms when two atoms share a pair of electrons, resulting in a lower energy state.

Question 8

Which of the following is true about the number of lobes and their orientation in a p orbital?

Accepted Answer

A p orbital has two lobes oriented along a straight line, with different algebraic signs.

Question 9

Which of the following best explains why the bond angle in methane (CH$_4$) is 109.5°?

Accepted Answer

The four sp$^3$ hybrid orbitals arrange themselves as far apart as possible, forming a tetrahedral geometry.

Question 10

In acetylene (C$_2$H$_2$), what is the hybridization of the carbon atoms and how are the bonds formed between them?

Accepted Answer

sp hybridization; one sigma ($\sigma$) and two pi ($\pi$) bonds

Question 11

Which of the following best describes the difference between a sigma ($\sigma$) bond and a pi ($\pi$) bond?

Accepted Answer

A sigma bond is formed by head-on overlap of orbitals, while a pi bond is formed by sideways overlap of p orbitals.

Question 12

Which of the following is the correct electron configuration for nitrogen (N) in its ground state?

Accepted Answer

$1s^2\ 2s^2\ 2p^3$

Question 13

A molecule of ethane (C$_2$H$_6$) is formed by the overlap of which orbitals between the two carbon atoms?

Accepted Answer

sp$^3$ hybrid orbitals from each carbon atom

Question 14

Which of the following statements about the energy released or absorbed during bond formation and breaking is correct?

Accepted Answer

Energy is released when a bond forms and absorbed when a bond breaks.

Question 15

Which of the following best describes the electron-dot (Lewis) structure for chloromethane (CH$_3$Cl)?

Accepted Answer

Carbon is bonded to three hydrogens and one chlorine, with chlorine having three lone pairs.

Question 16

Which of the following is a correct statement about the maximum number of electrons in the second shell of an atom?

Accepted Answer

The second shell can hold a maximum of 8 electrons.

Question 17

Which of the following best explains why the 4s orbital is filled before the 3d orbital in electron configurations?

Accepted Answer

The 4s orbital is lower in energy than the 3d orbital.

Question 18

In a line-bond (skeletal) structure, what does a vertex (intersection of two lines) typically represent?

Accepted Answer

A carbon atom with the appropriate number of hydrogens to complete four bonds.

Question 19

Which of the following is true about the orientation of sp$^2$ hybrid orbitals in ethylene (C$_2$H$_4$)?

Accepted Answer

They are arranged in a plane at 120° angles to each other.

Organic Chemistry: Structure and Bonding (Chapter 1 Study Notes)

Study Guide - Practice Questions