Chemical Bonding

Question 1

Chemical Bonds

Answer 1

the attractive forces that hold together atoms in most molecules

Question 2

Intramolecular Bonds

Answer 2

hold atoms together as molecules and include ionic and covalent bonds

Question 3

Intermolecular Forces

Answer 3

weaker bonds that hold together molecules

Question 4

Octet rule

Answer 4

• states that an atom tends to bond with other atoms until it has eight electrons in its outermost shell, thereby forming a stable electron configuration similar to that of the noble gas neon
• exceptions: hydrogen, helium, lithium, beryllium, boron, phosphorus and sulfur

Question 5

Ionic Bonding

Answer 5

• one or more electrons from an atom with a smaller ionization energy are transferred to an atom with a greater electron affinity, and the resulting ions are held together by electrostatic forces
• the electrostatic force of attraction between the charged ions
• they form crystal lattices consisting of arrays of positive and negative ions in which the attractive forces between ions of opposite charge are maximized, while the repulsive forces between ions of like charge are minimized
• have high melting and boiling points due to the strong electrostatic forces between the ions

Question 6

Covalent Bonding

Answer 6

• an electron pair is shared between two atoms

- have low melting points and do not conduct electricity in the liquid or aqueous states

Question 7

Polar Covalent Bonds

Answer 7

• the bond is partially covalent and partially ionic
• occurs between atoms with small differences in electronegativity
• the bonding electron pair is not shared equally but is pulled more toward the element with the higher electronegativity

Question 8

Cation

Answer 8

the atom that loses electrons becomes a positively charged ion

Question 9

Anion

Answer 9

the atom that gains electrons becomes a negatively charged ion

Question 10

Bond Order

Answer 10

the number of shared electron pairs between two atoms

Question 11

Bond Length

Answer 11

• the average distance between the two nuclei of the atoms involved in the bond
• as the number of shared electron pairs increases, the two atoms are pulled closer togehter, leading to a decrease in bond length

Question 12

Bond Energy

Answer 12

• the energy required to separate two bonded atoms

- increases as the number of shared electron pairs increases

Question 13

Bonding Electrons

Answer 13

the shared valence electrons of a covalent bond

Question 14

Non-boding electrons

Answer 14

the valence electrons not involved in covalent bond

Question 15

Lone electron pairs

Answer 15

the unshared electron pairs

Question 16

Lewis structure

Answer 16

-represent the bonding and non-bonding electrons in a molecule

Question 17

Lewis dot symbols

Answer 17

contains the symbol of an element and one “dot” for each valence electron in an atom

Question 18

Steps for assigning a Lewis structure to a molecule

Answer 18

1. Count all the valence electrons of the atoms. The number of valence electrons of the molecule is the sum of the valence electrons of all atoms present
2. Write the skeletal structure of the compound. The lease electronegative atom is the central atom. Draw single bonds between the sentral atom & the atoms surrounding it.
3. Complete the octets (8 valence electrons) of all atoms bonded to the central atom
4. Place any extra electrons on the central atom to form double or triple bonds
5. Finally, bonds are drawn as lines rather than pairs of dots

Question 19

Formal charge

Answer 19

V - 1/2 (Nbonding - Nnonbonding) or
V - (# of sticks + # of dots)

• a lewis structure with small or no formal charges is preferred over a Lewis structure with large formal charges
• a lewis structure in which negative formal charges are placed on more electronegative atoms is more stable than one in which the formal charges are placed on less electronegative atoms

Question 20

Resonance Structures

Answer 20

when molecules have two or more non-identical Lewis structures

Question 21

Polar molecule

Answer 21

a molecule that has such a separation of positive and negative charge

Question 22

Nonpolar covalent bond

Answer 22

• occurs between atoms that have the same electronegativities
• the bonding electron pair is shared equally such that there is no separation of charge across the bond
• occur in diatomic molecules such as H2, Cl2, O2, and N2

Question 23

Coordinate Covalent Bond

Answer 23

• the shared electron pair comes from the lone pair of one of the atoms in the molecule
• typically found in Lewis acid-base compounds

Question 24

Lewis acid

Answer 24

a compound that can accept an electron pair to form a covalent bond

Question 25

Lewis base

Answer 25

a compound that can donate an electron pair to form a covalent bond

Question 26

Valence shell electron-pair repulsion (VSEPR)

Answer 26

• uses Lewis structures to predict the molecular geometry of covalently bonded molecules
• steps that are used to predict the geometric structure of a molecule using the VSEPR theory:

1. Draw the Lewis structure of the molecule
2. Count the total number of bonding and nonbonding electron pairs in the valence shell of the central atom
3. Arrange the electron pairs around the central atom so that they are as far apart from each other as possible
4. Determine the bond angle, accounting for the additional repulsion due to nonbonding electrons, which pushes any bonding pairs slightly closer together.

Question 27

Bonding orbital

Answer 27

occurs when the signs of two atomic orbitals are the same

Question 28

Antibonding Orbital

Answer 28

when the signs of two atomic orbitals are different

Question 29

Sigma bond

Answer 29

when two orbitals of different atoms overlap head-to-head

Question 30

Pi bond

Answer 30

when parallel p orbitals interact

Question 31

van der Waals forces

Answer 31

forces not due to interactions of ions or hydrogen bonding

Question 32

van der Waals forces

Answer 32

forces not due to interactions of ions or hydrogen bonding

Question 33

Dipole-Dipole Interactions

Answer 33

present in the solid and liquid phases but become negligible in the gas phase because the molecules are generally much farther apart

Question 34

Hydrogen Boning

Answer 34

• strong form of dipole-dipole interaction
• have unusually high boiling points compared with compounds of similar molecular weight that do not hydrogen bond
• important in the behavior of water, alcohols, amines, and carboxylic acids

Question 35

Dispersion Forces

Answer 35

• the attractive interactions of short-lived dipoles

- generally weaker than other intermolecular forces

Question 36

Carbon-Carbon bonding

Answer 36

-can be categorized on length and energy level as well as hybridization