Unit 1 - Structure and Bonding Flashcards

1
Q

Rank these bonding types in order from least to most difference of electronegativity:

Polar covalent, ionic and pure covalent

A

1.Pure Covalent
2. Polar Covalent
3. Ionic

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2
Q

How can ionic bonds be formed?

A

When atoms with a large difference in electronegativity transfer electrons rather than share them.

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3
Q

True or False: The larger the difference in electronegativity, the more ionic in character the bond.

A

True

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4
Q

What do ionic compounds exist as?

A

Crystal lattice structures.

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5
Q

What is a covalent bond?

A

Where 2 positive nuclei share a common attraction for the negatively charged shared pair of electrons.

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6
Q

Explain hydrogen’s diatomic bonding.

A

The two atoms share electrons equally since each hydrogen atom has the same pull on the bonded electrons (same electronegativity).

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7
Q

What is a pure covalent bond/non-polar covalent bond?

A

When there is no difference in the electronegativity of the atoms. The electrons are shared equally and therefore there is no dipole in the bond.

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8
Q

What is a polar covalent bond?

A

When two atoms with different electronegativity values form covalent bonds resulting in an unequal sharing of electrons. This unequal sharing of electron leads to a dipole within the bond – an uneven distribution of charge. The atom with a higher electronegativity, pulls the electrons closer, making it slightly negative and leaving the other atoms slightly positive.

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9
Q

What do polar bonds have within them?

A

Permanent dipole

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10
Q

What is a permanent dipole?

A

A permanent unequal distribution of electrons in a bond.

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11
Q

Why does a molecules polarity depend on its arrangement?

A

Polar molecule contain polar covalent bonds which are not arranged symmetrically and so now negative poles and positive poles exist within the molecule (a permanent dipole).

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12
Q

Why does a molecules polarity depend on its arrangement?

A

Polar molecule contain polar covalent bonds which are not arranged symmetrically and so now negative poles and positive poles exist within the molecule (a permanent dipole).

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13
Q

How can a molecule contain polar bonds yet be non-polar?

A

The polar bonds are arranged symmetrically and so polarity cancels out.

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14
Q

Is water polar or non polar?

A

Polar

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15
Q

What is an experiment to distinguish polar and non-polar liquids?

A
  1. Full burette with liquid being tested.
  2. Charge a plastic rod.
  3. Open the burette and hold the charged rod close to the stream of liquid.

Stream deflects = polar liquid
Stream unaffected = non-polar liquid

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16
Q

What are the types of Van der Waals forces?

A
  1. LDF
  2. Permanent dipole - permanent dipole interactions
  3. Hydrogen bonding
17
Q

What is an intermolecular force?

A

Forces between molecules.

18
Q

What are LDF?

A

The weakest type of Van der Waals force. Occurs between all atoms and molecules.

19
Q

What causes LDF?

A

Constantly moving electrons causing an uneven distribution of electrons and thus the formation of temporary dipoles.

20
Q

True or false:
Larger atom = more electrons = stronger LDF

A

True

21
Q

What is a pd-pdi?

A

The electrostatic attraction between the oppositely charged parts of a dipole of two of more polar molecules. Occurs only between polar molecules.

22
Q

Is this a pd-pdi?

H—Cl- - - - -H—Cl

A

Yes (the dashed line)

23
Q

Why do polar molecules have stronger m.p than non-polar molecules?

A

Pd-pdi are stronger than LDF.

24
Q

What is hydrogen bonding?

A

A special type of pd-pdi. It exists between polar molecules that contain a Hydrogen atom directly bonded to a Fluorine, Nitrogen or Oxygen atom.

25
Q

What is the strongest Van der Waals force?

A

Hydrogen bonding

H bonding = high m.p

26
Q

True or False: Hydrogen bonding is stronger than covalent bonds.

A

FALSE

27
Q

Is this molecule polar or non-polar?

O=O

A

Non-polar.

  1. Both oxygen so electronegativities will be the same.
  2. The molecule is arranged symmetrically.
28
Q

What is the solubility rule?

A

“Like dissolves like.”

29
Q

Explain “like dissolves like.”

A

Polar solvents will dissolve charged/polar/ionic molecules.

Non-polar solvents will dissolve non-polar solutes.

30
Q

True or false: The stronger the Van der Waals forces between a liquid are, the more viscous it will be.

A

True

31
Q

What is viscosity?

A

Thickness.

e.g Oil is more viscous than water.

32
Q

The ____ hydrogen bonds there are, the more _____ it will be.

A
  1. more
  2. viscous
33
Q

Order these forces from most viscous to least.

pd-pdi
H bonding
LDF

A
  1. H bonding
  2. pd-pdi
  3. LDF

(The forces themselves are not viscous but the liquid they make up will be)

34
Q

What elements can be present in H bonds?

A

Hydrogen (necessary)
Fluorine
Oxygen
Nitrogen

35
Q

Are covalent bonds Van der Waals’ forces?

A

No