Bonding Flashcards

1
Q

What is an ionic bond?

A

An ionic bond is the electrostatic force of attraction between a positively charged ion and a negatively charged ion formed by electron transfer.

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2
Q

What is a covalent bond?

A

A covalent bond is the electrostatic force of attraction between a shared pair of electrons and their nuclei.

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3
Q

Why do ionic compounds have such high melting/boiling points?

A

Ionic compounds contain strong ionic bonds and is arranged in a lattice of positive and negative ions which requires lots of energy to overcome and hence has a high melting/boiling point.

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4
Q

Why is the melting point of MgO higher than that of NaCl?

A

The melting points are smaller when the ions are smaller (smaller atomic radius) or have higher charges.

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5
Q

What is Dative Covalent Bonding/Co-ordinate Bonding?

A

A dative covalent bond forms when the shared pair of electrons in the covalent bond come from only one of the bonding atoms.

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6
Q

What is Metallic bonding?

A

The electrostatic attraction between positive metal ions and negative delocalised electrons. ‘Positive metal ions in a sea of delocalised electrons’

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7
Q

When and why do Ionic compounds conduct electricity?

A

Ionic compounds conduct electricity when molten or aqueous as the ions can move freely and carry a charge.

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8
Q

What are the properties of ionic compounds and why?

A

They are brittle as when the layers slide over each other the ions line up with like charge ions and repel.

Ionic compounds conduct electricity when molten or aqueous as the ions can move freely and carry a charge.

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9
Q

What are the properties of Metallically bonded compounds?

A

They can conduct electricity as they have delocalised electrons which are free to move and carry a charge.

They are ductile and malleable as the layers can slide over each other without repelling and so can be drawn into wires or into other shapes.

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10
Q

What 3 factors effect the strength of a metallic bond?

A
  1. The number of protons/The strength of the nuclear attraction
  2. The size of the ion (The smaller the ion the greater stronger the bond)
  3. The number of delocalised electrons (The more delocalised electrons the stronger the bond)
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11
Q

What are the 5 ways to explain shape of a compound?

A
  1. State number of bonding pairs and lone pairs of electrons.
  2. State that electron pairs repel and try to get as far apart as possible
  3. If there are no lone pairs state that the electron pairs repel equally.
  4. If there are lone pairs of electrons, then state that lone pairs repel more than bonding pairs.
  5. State the actual shape and bond angle.
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12
Q

In what order do the following have the greatest repulsion from greatest to weakest: Bond-Bond, Lone-Lone and Lone-Bond?

A

Lone-Lone>Bond-Lone>Bond-Bond

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13
Q

What is electronegativity?

A

Electronegativity is the relative tendency of an atom to form a covalent bond in a molecule to attract electrons in a covalent bond to itself.

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14
Q

What are the 3 factors which effect electronegativity?

A
  1. The proton number (as proton number increases so does electronegativity).
  2. The atomic radius (as the atomic radius decreases the electronegativity increases).
  3. As the amount of shielding increases the electronegativity decreases.
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15
Q

What is the most electronegative element?

A

Fluorine

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16
Q

What difference on the Pauling scale creates an ionic bond?

A

1.9+

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17
Q

What difference on the Pauling scale creates a polar covalent bond?

A

0.4-1.8

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18
Q

What difference on the Pauling scale creates a non-polar covalent bond?

A

0.0-0.4

19
Q

What is a polar covalent bond?

A

A polar covalent bond has an unequal distribution of electrons in the bond and produces a charge separation.

20
Q

When is a molecule polar?

A

A molecule is polar when all of the electronegativities are pulling equally around a central atom and has a net 0

21
Q

When is a covalent bond polar?

A

A bond is polar when the difference in electronegativity is between 0.4-1.8.

22
Q

What are the three types of intermolecular forces?

A
  1. Van der Waals forces (induced dipole)
  2. Permanent dipole-dipole
  3. Hydrogen bonding
23
Q

What intermolecular forces are the strongest in order?

A
  1. Hydrogen bonding
  2. Permanent dipole dipole
  3. Van der Waals forces
24
Q

Why do the boiling points of halogens increase down the group?

A

As proton number increases the number of electrons increases and so does the size of the molecules. This creates greater Van der Waals forces and so requires more energy to overcome those intermolecular forces.

25
Q

Why do branch chain alkanes have lower boiling points than straight chain alkanes?

A

They have a larger surface area and their shape is slightly irregular and so cannot tessellate well enough so the Van der Waals forces aren’t as strong as they could be.

26
Q

What are the only three elements which can form hydrogen bonds?

A

Nitrogen, Oxygen and Fluorine

27
Q

Explain the boiling points of H2O, H2S, H2Se and H2Te?

A

As the elements move down the group, their atomic number increases and so they have greater Van der Waals forces and so require more energy to overcome those forces. Water is the exception however as it contains hydrogen bonds which require more energy to overcome than any of the intermolecular forces.

28
Q

When do hydrogen bonds form?

A

A hydrogen atom is bonded to a very electronegative atom will produce a strong partial positive charge and will have a lone pair of electrons and so will have hydrogen atoms attracted to the N/O/F atoms.

29
Q

How do Van der Waals forces work?

A

The distribution of charge in a molecule is always changing and if at one point the electrons all move to one side it will form a dipole and cause a chain reaction to other like molecules. The larger the molecule, the greater the strength of the Van der Waals forces.

30
Q

What should you look out for when drawing hydrogen bonds?

A
  1. Show all lone pairs
  2. Show all dipoles and all partial charges
  3. Show hydrogen bond from lone pair to hydrogen atom
31
Q

Linear

A

180 degrees

2 bond pairs

0 lone pairs

32
Q

Trigonal planar

A

120 degrees

3 bond pairs

0 lone pairs

33
Q

Tetrahedral

A

109.5 degrees

4 bonding pairs

0 lone pairs

34
Q

Trigonal pyramidal

A

107 degrees

3 bonding pairs

1 lone pair

35
Q

Trigonal Bipyramidal

A

90 degrees and 120 degrees

5 bonding pairs

0 lone pairs

36
Q

See-Saw

A

119 and 89 degrees

4 bonding pairs

1 lone pair

37
Q

Trigonal Planar/T-shape

A

120 degrees

3 bonding pairs

2 lone pairs (opposite each other)

38
Q

Octahedral

A

90 degrees

6 bonding pairs

0 lone pairs

39
Q

Square planar

A

90 degrees

4 bonding pairs

2 lone pairs

40
Q

Square Pyramidal

A

89 degrees

5 bonding pairs

1 lone pair

41
Q

Why is ice less dense than water?

A

The hydrogen bonding holds the water molecules away from each other.

42
Q

Bent

A

118 degrees

2 bonding
1 lone

43
Q

Bent 2 lone

A

104.5 degrees
2 bonding
2 lone