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Chemistry🧪 > P1: Bonding > Flashcards

P1: Bonding Flashcards

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1
Q

Define Electronegativity

A

The tendency/ability an atom to attract the bonding pair of electrons towards itself in a covalent bond.

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2
Q

What element has the highest electronegativity and why?

A
  • Fluorine
  • Has a small atomic radius so less shell shielding, but lots of protons so that it can strongly attract electrons.
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3
Q

What is ionic bonding in terms of electronegativity?

A

Two extremes of electronegativity (opposite) to be pure.

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4
Q

What is covalent bonding in terms of electronegativity?

A

Two almost equal amounts of electronegativity (pure)

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5
Q

What is a covalent bond between?

A

Non metal atoms.

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6
Q

What is an ionic bond between?

A

Metal and non metal atoms

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7
Q

What is a Dative bond?

A

Occurs when one atom provides both of the electrons for the covalent bond.

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8
Q

What does Isoelectronic mean?

A

Different elements, but the same electronic structure

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9
Q

What is a bonding pair?

A

Two shared electrons in a covalent bond

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10
Q

What is a lone pair?

A

Two electrons in a pair, not involved in bonding

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11
Q

Explain the ‘Linear’ shape of a molecule

A
  • Flat, in the plane
  • Bond angle of 180º, as the are repelling as far away as possible
  • 2 bonding pairs
  • 0 lone pairs
  • e.g CO2
         ◦-●-○
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12
Q

Explain the ‘Trigonal Planar’ shape of a molecule

A

-Flat, in the plane
-Bond angle of 120º
-3 bonding pairs
-0 lone pairs
-e.g BF3

-Upside down Y shape

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13
Q

Explain the ‘Tetrahedral’ shape of a molecule

A

-2 bond in the plane, 2 bonds out of the plane
-Bond angle of 109.5º
-4 bonding pairs
-0 lone pairs
-e.g CH4

-so one bond will go towards me, one will go behind

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14
Q

Explain the ‘Octahedral’ shape of a molecule

A

-2 bonds in the plane, 4 bonds out of the plane
-Bond angle of 90º
-6 bonding pairs
-0 lone pairs
-e.g SF6

-Top and bottom in the plane, two towards me, two going behind

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15
Q

Explain the ‘Trigonal Bi-Pyramidal’ shape of a molecule

A

-3 bonds in the plane, 2 out of the plane
-Bond angle of 90º between the top and side bonds, and then 120º between the side bonds
-5 bonding pairs
-0 lone pairs
-e.g PF5

-Top, bottom and left in the plane, one towards, one behind

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16
Q

By what degree does having a lone pair push the other bonds down by?

A

2.5º

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17
Q

How are lone pairs different to bonding pairs in terms of repulsion?

A

-Lone pairs are more compact and closer to the nucleus, which therefore means they provide more repulsion.
-The greatest repulsion comes from two lone pairs, and the weakest is two bonding pairs

18
Q

Describe the ‘Trigonal Pyramidal’ shape of a molecule

A

-3 bonding pairs
-1lone pair
- The lone pair at the top pushes the bond angles down by 2.5º. so its not 109.5º its actually 107º

-Lone pair at the top, one bond in the the plane, one towards, one behind

19
Q

Describe the ‘Square planar’ shape of a molecule

A

-4 bonding pairs
-2 lone pairs
-Still a bond angle of 90º (octahedral) because the lone pairs placement mean the forces even out and don’t change anything

  • Lone pairs at the top and bottom to be as far away from each other as possible, then 2 behind, 2 towards
  • Becomes a flat shape
20
Q

Explain the ‘Non Linear’ shape of a molecule

A

-e.g water
-2 lone pairs
-2 bonding pairs
-2 lone pairs which push the other bonds down, so it can be a straight shape, its bent
- Because these 2 lone pairs are next to each other at the top, their forces add together: 2.5+2.5= 5
-Therefore the bond angle is X-5
-104.5

-An upside down V shape, 2 lone pairs at the top, 2 bonds at the bottom

21
Q

What are the properties of a metallic bond?

A

-Melting point: Very high, electrostatic forces
-Conductivity solid: ✓ free electrons
-Conductivity liquid: ✓ free electrons
-Conductivity aqueous: ✗ insoluble
-Soluble in water: ✗

22
Q

What are the properties of an ionic bond?

A

-Melting point: High, electrostatic forces
-Conductivity Solid: ✗ no free electrons
-Conductivity Liquid: ✓ lattice is broken, ions can move
-Conductivity Aqueous: ✓ ions free to move
-Soluble in water: ✓ water breaks down lattice by getting in-between molecules

23
Q

What are the properties of a simple molecular bond?

A

-Melting point: Low, weak intermolecular forces
-Conductivity Solid: ✗ no free electrons or ions
-Conductivity Liquid: ✗
-Conductivity Aqueous: ✗
-Soluble in water: Depends on the molecule

24
Q

What are the properties of a giant covalent molecule?

A

Melting point: Very high, electrostatic forces
Conductivity Solid: ✗, apart from graphite
Conductivity Liquid: ✗
Conductivity Aqueous: ✗
Soluble in water: ✗, imissible

25
Q

What are the elements that will form a polar bond?

A

Nitrogen (N), Oxygen (O), Fluorine (F),
Chlorine (Cl), Bromine (Br)

-Partially negative

26
Q

Define what a ‘polar bond’ is

A

A covalent bond where the atoms have unequal attraction because one element is more electronegative than the other so is unequal; a dipole.

27
Q

What does lowercase delta (d) mean?

A

Means a partial charge in a polar bond: therefore will be d- or d+

28
Q

How do you show polar bonds?

A

-A partially negative sign (d-) next to the most electronegative element (one of N,O,F,Cl,Br)
-A partially positive sign (d+) next to the other elements
-An arrow going towards the negative (where the energy is going)

29
Q

Describe ‘Van der Waals’ forces (VDW)

A

-AKA induced dipole-dipole forces
-An instantaneous dipole is formed when the electron density in a molecule/atom is in an instant uneven due to movement of electrons, creating a non-permanent dipole.
-This dipole can the induce a dipole in the next molecule along as the two negative charges will repel and create a partial positive charge.
-Occurs in non-polar bonds
-Weakest form of force

30
Q

Describe a ‘permanent dipole-dipole’ force

A

-The attraction of a partial negative charge in one molecule attracting the partial positive charge of another molecule, creating a permanent attraction.
-Occurs in polar bonds

31
Q

Describe ‘hydrogen bonding’ forces

A

-Not an actual bond, its a force
-A hydrogen atom bonded to a very electronegative element with a lone pair, so F, O, N
-The hydrogen will be attracted to the lone pairs, where the force is.
-This is the strongest type of intermolecular force.
-Occurs in polar bonds

e.g H-F attracted to :N-

32
Q

What is the second type of ‘Non-linear/bent’ shape?

A

-2 bonding pairs
-2 lone pairs
-Bond angle: 118

looks like v upside down

33
Q

Explain the ‘Trigonal bi-pyramidal/seesaw’ obscure shape

A

-4 bonding pairs
-1 lone pair
-Bond angle: 102 and 87

lone pair at top, bonding pairs in a fan shape at bottom

34
Q

Explain the ‘T-shaped’ shape

A

-3 bonding pairs
-2 lone pairs
Bond angle: 88

35
Q

Explain the linear obscure shape

A

-3 bonding pairs
-2 lone pairs
-bond angles: 180

2 lone pairs on one side
1 on the other

36
Q

What is a step by step process of predicting a shape of a molecule?

A
  1. Draw dot and cross diagrams
  2. Count number of electron pairs around the central atom
  3. Identify electron pair arrangement
  4. Identify lone pairs and bonding pairs
37
Q

Does electronegativity decrease or increase across a period?

A

Increase

38
Q

Does electronegativity increase or decrease down a group?

A

Decrease

39
Q

Why does Hydrogen have the same electronegativity as carbon (or very similar)?

A

It has no shielding

40
Q

What is the Pauling scale?

A

-A numerical measure of electronegativity
-Higher the value, the more electronegative the element is.

A difference greater than 0.5 is a dipole/polar bond.

41
Q

What are the rules when deciding if a molecule is polar?

A
  1. No polar bonds= not a polar molecule
  2. Polar bonds that are all on one side of central atom= polar molecule
  3. Molecule with all the same type of polar bond e.g C-Cl= not polar, cancel out
  4. Polar bonds, with at least one different type of polar bond= polar molecule

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