Bonding 1 Ionic, Metalic, & Covalent

Question 1

Hypothesis by Lewis

Answer 1

Atoms react (by forming ions or sharing electrons) in order to obtain the electronic configuration of a noble gas (for maximum stability)

Question 2

Lewis Dot Structures

Answer 2

• The periodic table allows us to determine the likely reactivity of atoms
• We can use Lewis dot structures to keep track of the valence electrons in an atom
• Elements in the same group have the same valence electronic configuration, and so, the same number of dots
• If an atom has more than four valence electrons, then the electrons are paired up (but not before!)
• The number of valence electrons (and thus the number of dots) is equal to the group number

Question 3

Lewis Dot Structure Exception

Answer 3

Helium - Is in group 8 which means it should have 8 valence = 8 dots but it does NOT
Helium = 2 dots

Question 4

Ionic Bond

Answer 4

The electrostatic force that holds the oppositely charged ions together in an ionic compound, or ions with completely different electronegativities

Question 5

Lattice Energy

Answer 5

• The energy required to separate 1 mol of a solid ionic crystalline compound into its gaseous ions
• We can measure the stability of an ionic solid by lattice energy

Question 6

Coulomb’s Law

Answer 6

If we know the structure of the ionic compound, we can calculate the lattice energy by using Coulomb’s Law

Question 7

Coulomb’s Law Formula

Answer 7

      rLi-F Since one of the charges is negative, this value will always be < 0 (there will always be attraction)

Question 8

Trends in Lattice Energies

Answer 8

• Ions with greater charge create lattices with a higher lattice energy (from Coulomb’s law)
• Smaller ions get closer together, increasing the interaction between them (and thus the lattice energy)
• Melting points tend to increase with lattice energy

Question 9

Covalent Bond

Answer 9

A bond in which two electrons are shared by two atoms EQUALLY

Question 10

True or False: Compounds that contain only covalent bonds are
called covalent compounds

Answer 10

TRUE

Question 11

Lone Pairs

Answer 11

Nonbonding electrons are called lone pairs (they are single electrons)

Question 12

Covalent Bonds and Lewis Structures

Answer 12

• Covalent bonding between atoms only involves the valence electrons
• Covalent compounds can be shown by drawing Lewis structures, which are a molecular extension to the Lewis dot symbols for atoms

Question 13

Lewis Structure Define:

Answer 13

A representation of covalent bonding in which shared electron pairs are shown either as lines or as pairs of dots between two atoms, and lone pairs are shown as pairs of dots on individual atoms

Question 14

Multiple Bonds

Answer 14

• Atoms can be held together by more than one electron pair
• Known as multiple bonds, which
  are bonds formed when two atoms share two or more pairs of electrons
• If two electron pairs are shared, it is called a double bond; if three pairs are shared it is a triple bond
  Ex: Double bond (Carbon dioxide)
  Ex: Triple bond (Nitrogenous gas)

Question 15

Lone Pair Exception

Answer 15

Carbon Monoxide

Question 16

True or False: It always takes energy to break a bond?

Answer 16

TRUE

Question 17

Corollary Defined

Answer 17

Energy is released when a bond is formed

Question 18

Bond Dissociation Energy

Answer 18

Amount of energy required to break a mole of bonds of a certain type

Question 19

Higher bond dissociation energy =

Answer 19

= stronger chemical bond

Question 20

Polar Covalent Bonds Defined

Answer 20

A pair of electrons is unequally shared between two atoms

Question 21

Nonpolar Covalent Bonds Defined

Answer 21

Two atoms share a pair of electrons with each other

Question 22

Electronegativity and Bonding

Answer 22

Atoms that are = to or > that 1.7 means its ionic

Question 23

Octet Rule

Answer 23

Main-group elements tend to bond in a way that each atom has eight electrons in its valence shell, giving it the same electronic configuration as a noble gas

Question 24

Formal Charge Defined

Answer 24

The electrical charge difference between the valence electrons in an isolated atom and the number of electrons assigned to that atom in a Lewis structure

Question 25

Formal charges can also be used to distinguish between different possible Lewis structures for a molecule:

Answer 25

1) A structure with no formal charges is preferred over one with formal charges 2) Structures with smaller formal charges (± 1) are preferred over those with larger ones (± 3) 3) More stable structures should have negative formal charges on the more electronegative atoms

Question 26

Resonance Defined

Answer 26

The use of two or more Lewis structures to represent a particular molecule

Question 27

Exceptions to the Octet Rule

Answer 27

– Incomplete octet – Odd number of electrons – More than 8 electrons around the central atom

Question 28

Incomplete Octet

Answer 28

- In some compounds the number of electrons surrounding the central atom is less than 8 - This mostly happens with elements on the left side of the periodic table when they form molecular compounds (for our purposes just Be, B, and Al)

Question 29

Odd-Electron Molecules

Answer 29

- Some molecules contain an odd number of electrons - These molecules cannot obey the octet rule for all atoms, since at least one atom must have an unpaired electron - These are paramagnetic, and are sometimes called (free) radicals - Many radicals are highly reactive

Question 30

Expanded Octet

Answer 30

- Second-period atoms cannot have more than 8 valence electrons around the central atoms, but atoms in the third (and below) periods can - Ex: SF6 - All six of sulphur’s valence electrons form bonds with fluorine

Question 31

Metallic Bonding

Answer 31

The electron-sea model to describe the bonding In metals