Chapter 1.2: Lewis Model of Bonding

Question 1

What is an atom or group of atoms bearing a positive charge?

Answer 1

cation

Question 2

Define nonbonding electrons

Answer 2

valence electrons not involved in forming a covalent bond; unshared pairs or lone pairs

Question 3

What group of elements have exceptions to the octet rule?

Answer 3

Group 3A elements

Question 4

What is energy added or released when an electron is added to an atom or molecule?

Answer 4

electron affinity

Question 5

What is a measure of the force of an atom’s attraction for electrons?

Answer 5

electronegativity

Question 6

Define bond length

Answer 6

the distance between atoms in a covalent bond in picometers

Question 7

Define electron affinity

Answer 7

energy added or released when an electron is added to an atom or molecule

Question 8

Why does electronegativity decrease down a group?

Answer 8

• Decreases down a group because the increasing distance of the valence electrons from the nucleus results in a lower attraction between the nucleus and these electrons

Question 9

What is the distance between atoms in a covalent bond in picometers?

Answer 9

bond length

Question 10

Why does electronegativity increase within a period?

Answer 10

• Increase within a period because of the increasing positive charge on the nucleus results in a greater force of attraction for the atom’s valence electrons

Question 11

Define electronegativity

Answer 11

a measure of the force of an atom’s attraction for electrons

Question 12

What is group 1A-7A elements react to achieve an outer shell of eight valence electrons?

Answer 12

octet rule

Question 13

What is attraction between oppositely charged ions?

Answer 13

ionic interaction

Question 14

How are ions formed?

Answer 14

• Ions are formed by the transfer of electrons from the valence shell of an atom of lower negativity to the valence shell of an atom of higher electronegativity
• Ions form when difference in electronegativity is 1.9 or greater

Question 15

What are Dative bonds?

Answer 15

o Construction of a Lewis structure from neutral groups or atoms to achieve an octet gives rise to bonds where the two electrons come from only a single groups or atom while the other group or atom involved in that bond does not contribute any electrons. Such bonds are referred to as dative or coordinate covalent

Question 16

Define formal charge

Answer 16

the charge of an atom in a polyatomic ion or molecule

Question 17

What are valence electrons not involved in forming a covalent bond; unshared pairs or lone pairs?

Answer 17

nonbonding electrons

Question 18

Define cation

Answer 18

an atom or group of atoms bearing a positive charge

Question 19

Define bond dipole moment

Answer 19

a measure of the polarity of a covalent bond; the product of the charge on either atom of a polar bond times the distance between the atoms

Question 20

What is a chemical bond formed between two atoms by sharing one or more pairs of electrons?

Answer 20

covalent bond

Question 21

What is a covalent bond between atoms whose difference in electronegativity is between 0.5 and 1.9?

Answer 21

polar covalent bond

Question 22

Define bonding electrons

Answer 22

valence electrons involved in forming a covalent bond (shared electrons)

Question 23

What is the formula for formal charge?

Answer 23

o Formal Charge = number of valence electrons in the neutral, unbonded atom – (all unshared electrons + one half of all shared electrons)

Question 24

What is an atom or group of atoms bearing a negative charge?

Answer 24

anion

Question 25

What are different compounds with same molecular formula?

Answer 25

isomers

Question 26

Define isomer

Answer 26

different compounds with same molecular formula

Question 27

Define polar covalent bond

Answer 27

a covalent bond between atoms whose difference in electronegativity is between 0.5 and 1.9

Question 28

Describe the period trend of electronegativity

Answer 28

 Generally, increase from left to right on Periodic Table and decrease from top to bottom

Question 29

What are the guidelines of drawing Lewis Dot Structures?

Answer 29

 Determine the number of valence electrons in the molecule or ion
 Determine the connectivity (arrangement) of atoms in the molecule or ion
 Connect the atoms with single bonds
 Each pair of electrons shared between two atoms is shown as a single line between the atoms. Each unshared pair of electrons is shown as a pair of dots

Question 30

What is a polar covalent bond?

Answer 30

o Bonds may be partially ionic and partially covalent (aka polar covalent bond)

Question 31

Define nonpolar covalent

Answer 31

a covalent bond between atoms whose difference in electronegativity is less than 0.5

Question 32

What is a covalent bond between atoms whose difference in electronegativity is less than 0.5?

Answer 32

nonpolar covalent

Question 33

Define covalent bond

Answer 33

a chemical bond formed between two atoms by sharing one or more pairs of electrons

Question 34

What are valence electrons involved in forming a covalent bond (shared electrons)?

Answer 34

bonding electrons

Question 35

Define octet rule

Answer 35

group 1A-7A elements react to achieve an outer shell of eight valence electrons

Question 36

What is a measure of the polarity of a covalent bond; the product of the charge on either atom of a polar bond times the distance between the atoms?

Answer 36

bond dipole moment

Question 37

Define anion

Answer 37

an atom or group of atoms bearing a negative charge

Question 38

Define ionic interaction

Answer 38

attraction between oppositely charged ions

Question 39

What is the charge of an atom in a polyatomic ion or molecule?

Answer 39

formal charge