Chemical Bonding

Front 1

Define Lewis diagram

Back 1

A structural formula in which valence electrons are represented by dots or crosses.

Front 2

Define valence electron

Back 2

The electrons in the highest energy level of an atom in which there are electrons.

Front 3

Define a chemical bond

Back 3

A mutual attraction between two atoms resulting from the simultaneous attraction between their nuclei and outer electrons.

Front 4

Which is smaller: energy of two bonded atoms or energy of individual atoms? What does this result in?

Back 4

The energy of the combined atoms is smaller. This results in higher stability in bonded atoms.

Front 5

How do atoms make more than 4 bonds?

Back 5

One of the electrons in a lone pair in a 3s or 3p orbital can move to the 3d orbital.

Front 6

Give an example of: 1) an element that can form 5 bonds and 2) an element that can form 6 bonds.

Back 6

1) phosphorus (5 bonds) -e.g. PCl5

2) sulphur (6 bonds) -e.g. SF6

Front 7

What is the difference between a single bond and multiple bonds?

Back 7

Atoms joined by single bonds can rotate around the bond, whereas atoms joined by multiple bonds are held in a fixed position.

Front 8

Give examples of atoms that cam form: 1) double bonds and 2) triple bonds

Back 8

1) oxygen

2) nitrogen

Front 9

Give the formula and couper diagram for hydrogen cyanide.

Back 9

HCN

Front 10

How are dative covalent bonds formed?

Back 10

Dative covalent bonds are formed by the overlapping of a filled orbital containing a lone pair with the empty orbital of another atom or ion.

Front 11

Give two examples of when dative covalent bonds are formed.

Back 11

When an H+ ion joins to a water molecule to form H3O+.

When an H+ ion joins to an ammonia molecule to form the ammonium ion, NH4+.

Front 12

Show, by means of a Lewis diagram, how H3O+ is formed.

Back 12

Front 13

Show, by means of a Lewis diagram, how the ammonium ion is formed.

Back 13

Front 14

Define a covalent bond

Back 14

The sharing of electron between two atoms to form a molecule.

Front 15

Define a molecule.

Back 15

A group of two or more atoms covalently bonded and that function as a unit.

Front 16

Why can two He atoms not form a chemical bond?

Back 16

Different atoms with paired valence electrons (lone pairs) cannot share these 4 electrons to make a bond, according to the rules of bond formation.

Front 17

Define a bonding pair

Back 17

A pair of electrons that is shared between two atoms

Front 18

Define a lone pair

Back 18

A pair of electrons in the valence shell of an atom that is not shared with another atom.

Front 19

What does the shape of a molecule depend on?

Back 19

The number of bonding electron groups and lone pairs on the central atom.

Front 20

What shape, bond angle, and symmetry (yes/no) will a molecule with 1 bonding pair have?

Back 20

Linear, 180°, asymmetrical

Front 21

What shape, bond angle, and symmetry (yes/no) will a molecule with 2 bonding pairs have?

Back 21

Linear, 180°, symmetrical

Front 22

What shape, bond angle, and symmetry (yes/no) will a molecule with 3 bonding pairs have?

Back 22

Trigonal planar, 120°, symmetrical

Front 23

What shape, bond angle, and symmetry (yes/no) will a molecule with 4 bonding pairs have?

Back 23

Tetrahedral, 109°, symmetrical

Front 24

What shape, bond angle, and symmetry (yes/no) will a molecule with 5 bonding pairs have?

Back 24

Trigonal bi-pyramid, 120° in the plane and 90° at top and bottom, symmetrical

Front 25

What shape, bond angle, and symmetry (yes/no) will a molecule with 6 bonding pairs have?

Back 25

Octahedral, 90°, symmetrical

Front 26

What shape, bond angle, and symmetry (yes/no) will a molecule with 3 bonding pairs and one lone pair have?

Back 26

Pyrammidal, 107,5°, asymmetrical

Front 27

What shape, bond angle, and symmetry (yes/no) will a molecule with 2 bonding pairs and 2 lone pairs have?

Back 27

Angular, 109°, asymmetrical

Front 28

Define electronegativity

Back 28

A measure of the tendency of an atom in a molecule to attract bonding electrons

Front 29

Define non-polar bond

Back 29

A bond in which the electron density is shared equally between the two atoms.

Front 30

Define polar covalent bond

Back 30

A bond in which the electron density is shared unequally between the two atoms

Front 31

In which region of difference in electronegativity will a bond be ionic?

Back 31

EN > 2,1

Front 32

In which region of difference in electronegativity will a bond be polar covalent?

Back 32

EN > 1

Front 33

EN < 1

Back 33

Very weakly polar covalent

Front 34

EN = 0

Back 34

Pure covalent / non-polar covalent

Front 35

2 vases for non-polar molecules

Back 35

When there are non-polar bonds (EN = 0)

When there are polar bonds, but the molecule is symmetrical

Front 36

Define bond energy

Back 36

The energy needed to break one mole of compound's molecules into separate atoms.

Front 37

Define bond length

Back 37

The average distance between the nuclei of two bonded atoms.

Front 38

What is the relationship between bond energy and bond length?

Back 38

Bonds with a shorter bond length require more energy to break then bonds with a longer bond length. (As bond length increases, bond energy decreases.)

Front 39

What is the relationship between the strength of a chemical bond and the length of the bond between two atoms?

Back 39

If the force if attraction between two atoms is strong, the nuclei will come very close together, resulting in a short bond length.

Front 40

What is the relationship between the strength of a chemical bond and the size of the bonded atoms?

Back 40

The bond length between larger atoms is longer than the bond length between smaller atoms. Therefore, larger atoms will have weaker bonds.

Front 41

What is the relationship between the strength of a chemical bond and the number of bonds between the atoms?

Back 41

Bond strength increases as the number of bonds between atoms increases.

Front 42

What is happening at point 1?

Back 42

The atoms are far apart, there is no interaction between them and the potential energy is almost zero.

Front 43

What is happening at point 2?

Back 43

As the atoms approach, the potential energy decreases because the nucleus from one atom attracts the electron cloud from the other.

Front 44

What is happening at point 3?

Back 44

The lowest energy level value means this is the most stable position and the atoms bond by sharing electrons.

Front 45

What is happening at point 4?

Back 45

The atoms approach too closely. There is repulsion between the nuclei; the potential energy rises, so this is not a stable position. The atoms return to position 3.

Front 46

What do d and E represent?

Back 46

d - bond length

E - bond energy