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Chemistry > Shapes of molecules/bonding and structure > Flashcards

Shapes of molecules/bonding and structure Flashcards

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1
Q

What is an ionic bond?

A

An electrostatic attraction between oppositely charged ions (metal and non-metal)

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2
Q

What must an ionic dot-and-cross diagram include?

A

Square brackets and the charge of the ion must be shown

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3
Q

What is a covalent bond?

A

An electrostatic attraction between the nuclei of the bonded atoms and a shared pair of electrons (two non-metals)

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4
Q

How many bonding pairs of electrons would O = O have?

A

2

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5
Q

What is a dative covalent bond?

A

Where one of the atoms supplies both of the electrons to the covalent bond

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6
Q

What symbol is used to represent extra electrons causing charge in a negative ion?

A

Triangle

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7
Q

How is the shape of a molecule determined?

A

By the number of electron pairs in the outer shell of the central atom (bonding and lone)

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8
Q

What is an intermolecular force?

A

An attractive force between neighbouring molecules

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9
Q

What are the 3 types of intermolecular force?

A
  1. Induced dipole-dipole/London
  2. Permanent dipole-dipole
  3. Hydrogen bonding
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10
Q

Which types of molecule have London/permanent dipole-dipole/hydrogen forces?

A

London - all molecules
Permanent dipole-dipole - polar molecules
Hydrogen - molecules with O-H, H-N or H-F bonds

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11
Q

What is a permanent dipole?

A

When two atoms of different electronegativities are bonded together

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12
Q

How do induced dipole-dipole forces form?

A
  1. Uneven distribution of electrons within each molecule (random movement)
  2. Creates an instantaneous dipole
  3. Induces a dipole in the neighbouring molecule
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13
Q

Why does boiling point increase from Cl2 to Br2 to I2?

A
  1. All have induced dipole-dipole forces between molecules
  2. Going down the group, no. electrons increases which increases the strength of the IMF
  3. Require more energy to break
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14
Q

What must you do when drawing a hydrogen bond?

A
  1. Include dipoles
  2. 180° angle
  3. Draw bond from the lone electron pair
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15
Q

What is the definition of a hydrogen bond?

A

A stronger dipole-dipole attraction between a hydrogen atom on one molecule and a lone pair of electrons on a highly electronegative atom on a different molecule

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16
Q

What is the definition of electronegativity?

A

The ability an atom has to attract the bonding pair of electrons in a covalent bond

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17
Q

Which elements have more electronegativity?

A

Those at the TOP RIGHT of the Periodic table (N, O, F)

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18
Q

What is a non-polar bond?

A

Where the atoms are identical and so their electronegativities are equal

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19
Q

What is a polar bond?

A

Where the atoms are different so one will be more electronegative than the other

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20
Q

What makes a MOLECULE polar?

A

If it has polar bonds and is not symmetrical

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21
Q

What makes a molecule symmetrical?

A

If there are no lone pairs and all of the bonds are the same

22
Q

What happens if a molecule is symmetrical?

A

The dipoles cancel out

23
Q

Which particular bond is always non-polar?

A

C-H

24
Q

What are the 2 anomalous properties of H2O?

A
  1. Relatively high boiling point - stronger hydrogen bonds need to be broken
  2. Ice less dense than water - molecules are held further apart by hydrogen bonds in a lattice
25
Q

What is the shape and bond angle of a molecule with 2 bonding pairs?

A

Linear, 180°

26
Q

What is the shape and bond angle of a molecule with 3 bonding pairs?

A

Trigonal planar, 120°

27
Q

What is the shape and bond angle of a molecule with 4 bonding pairs?

A

Tetrahedral, 109.5°

28
Q

What is the shape and bond angle of a molecule with 6 bonding pairs?

A

Octahedral, 90°

29
Q

How are lone pairs different to bonded pairs?

A

They repel more

30
Q

What is the shape and bond angle of a molecule with 3 bonding pairs and 1 lone pair?

A

Pyramidal, 107°

31
Q

What is the shape and bond angle of a molecule with 2 bonding pairs and 2 lone pairs?

A

Non-linear, 104.5°

32
Q

Why is SF6 octahedral?

A
  1. It has 6 bonding pairs of electrons around sulfur

2. Electron pairs repel each other

33
Q

Why is NH3 pyramidal?

A
  1. It has 3 bonding pairs and 1 LONE PAIR of electrons around nitrogen
  2. Electron pairs repel each other and lone pairs REPEL MORE than bonding pairs
34
Q

What are bonding pairs called instead when the molecule has double bonds?

A

Bonding regions

35
Q

In what types of compound are ionic bonds found?

A

Metal and non-metal

36
Q

In what types of compound are covalent bonds found?

A

Non-metal and non-metal

37
Q

What is the definition of a giant ionic lattice?

A

A regular and repeating structure of oppositely charged ions

38
Q

What do “giant” and “simple” mean in terms of lattices?

A 
Giant = made up of ATOMS
Simple = made up of MOLECULES
39
Q

What does “like dissolves like” refer to?

A

Polar solutes dissolving in polar solvents and non-polar solutes dissolving in non-polar solvents

40
Q

What is metallic bonding?

A

A strong electrostatic attraction between positive metal ions and the sea of delocalised electrons

41
Q

What is a giant metallic lattice?

A

Metal ATOMS held together as a lattice of positive ions surrounded by a sea of delocalised electrons

42
Q

Why are metals good conductors of electricity?

A

They have mobile charge carriers (delocalised electrons)

43
Q

Do ionic compounds have a high melting point?

A

Yes - large amounts of energy needed to break many strong bonds

44
Q

Do ionic compounds conduct electricity when solid?

A

No - ions are held firmly in place so no mobile charge carriers

45
Q

Do ionic compounds conduct electricity when molten/aqueous?

A

Yes - ions are free to move (so mobile charge carriers)

46
Q

What structure and IMFs does iodine (I2) have?

A

Simple covalent lattice (made up molecules), induced dipole-dipole forces (not polar)

47
Q

What are the properties of GIANT IONIC lattices?

A
  • High melting points (strong ionic bonds)
  • High solubility in polar solvents, low solubility in non-polar solvents
  • Low electrical conductivity when solid, high electrical conductivity when molten/aqueous (mobile charge carriers)
48
Q

What are the properties of SIMPLE COVALENT lattices?

A
  • Low melting points (weak induced dipole-dipole forces between molecules)
  • High solubility in polar solvents if molecule is polar, high solubility in non-polar solvents if molecule is non-polar
  • Low electrical conductivity when solid and molten/aqueous (no mobile charge carriers)
49
Q

What are the properties of GIANT COVALENT lattices (diamond, graphite/graphene, Si and SiO2)

A
  • High melting points (atoms bonded covalently)
  • Low solubility in polar/non-polar solvents
  • Low electrical conductivity when solid or molten/aqueous (except for graphite - delocalised electrons)
50
Q

What are the properties of GIANT METALLIC lattices?

A
  • High melting points (metallic bonds)
  • Low solubility in polar/non-polar solvents (bonds aren’t easily broken)
  • High electrical conductivity when solid and molten/aqueous (delocalised electrons are free to move)

Chemistry (29 decks)

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