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Chemistry > Bonding > Flashcards

Bonding Flashcards

1
Q

What is a compound?

A

When different elements join or bond together, you get a compound. The bonding in compounds is either ionic or covalent.

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1
Q

When are ions formed?

A

Ions are formed when atoms are transferred from one atom to another.

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2
Q

Why do elements in the same group form ions with the same charge?

A

They all have the same number of electrons in their outer shell

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3
Q

What is ionic bonding?

A

The electrostatic attraction between positive ions and negative ions

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4
Q

What is the charge and formula of the compound ion: Sulphate?

A

SO4^2-

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5
Q

What is the charge and formula of the compound ion: Hydroxide?

A

OH^-

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6
Q

What is the charge and formula of the compound ion: Nitrate?

A

NO3^-

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7
Q

What is the charge and formula of the compound ion: Carbonate?

A

CO3^2-

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8
Q

What is the charge and formula of the compound ion: Ammonium?

A

NH4^+

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9
Q

What structures do ionic compounds form?

A

They form giant ionic lattices
It is made up of the same basic uni repeated over again

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10
Q

Do ionic compounds conduct electricity?

A

only when molten or aqueous as that is when ions are free to move and carry charge

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11
Q

Why do ionic compounds have high melting points?

A

They are held together by strong electrostatic forces of attraction which requires a lot of thermal energy to break, which leads to high melting and boiling points.

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12
Q

Why do ionic compounds dissolve in water?

A

Water molecules are polar. These charged areas pull ions away from the lattice, causing it to dissolve.

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13
Q

What are molecules?

A

Molecules form when two or more atoms bond together. They are held together by strong covalent bonds.

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14
Q

What is a covalent bond?

A

A covalent bond is an electrostatic force of attraction between the negatively charged shared pair of electrons and the positive nuclei of the atoms.

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15
Q

What kind of structures do covalent bonds make up?

A

Both molecular and Giant
Giant covalent structures have a huge network of covalently bonded atoms. (also called macromolecular structures)

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16
Q

What are the four allotropes of carbon?

A
  • Diamond
  • Graphite
  • Buckminterfullerine
  • Graphene
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17
Q

Why is graphite used as a lubricant?

A

The weak van der Waal forces between the layers are easily broken allowing the layers to slide over one another, making it a good lubricant.

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18
Q

Why is graphite an electrical conductor?

A

The delocalized electrons in graphite are able to move and carry charge.

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19
Q

Why does graphite have a low density?

A

The layers are quite far apart compared to the length of the covalent bonds, so graphite has a low density and is used to make strong, lightweight sports equipment.

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20
Q

Why does graphite have a very high melting point?

A

because of the strong covalent bonds in the hexagon sheets, graphite has a very high melting point (it sublimes over 3900K)

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21
Q

Why is graphite insoluble in any solvent?

A

The covalent bonds in the sheet are too strong to break

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22
Q

What is the structure of diamond?

A

Diamond is made up of carbon atoms. Each carbon atom is covalently bonded to four other carbon atoms. The atoms arrange themselves in a tetrahedral shape.

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23
Q

Due to its strong covalent bonds what properties does diamond have?

A
  • High melting point
  • Diamond is extremely hard
  • vibrations travel easily so it’s a good thermal conductor
  • it cant conduct electricity
  • it won’t dissolve in any solvent
  • You can cut diamond to form gemstones as it reflects light
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24
Q

What is dative covalent bonding?

A

Dative covalent bonding is where both electrons come from one atom.

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25
Q

What are charge clouds?

A

A charge cloud is an area where you have a really big chance of finding an electron pair.

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26
Q

What determines the angles in the shape of a molecule? (valence shell repulsion theory)

A

Electrons are negatively charged so repel one another, so the charge clouds will repel one another as much as they can. Lone pair charge clouds repel more than bonding pair charge clouds. So the greatest angles are between lone pairs of electrons, and bond angles between bonding pairs are often reduced because they are pushed together by lone pairs.

27
Q

How do you calculate the number of lone and bonding pairs on a molecule?

A

1) work out the central atom
2) work out number of outer shell electrons on it
3) add one for every atom it is bonded to
4) divide by 2
5) compare the number of electron pairs to the number of bonds to find the number of lone pairs and the number of bonding pairs

28
Q

What is a molecule called with 2 electron pairs and no lone pairs?

A

linear - 180

29
Q

What is a molecule called with 3 electron pairs and no lone pairs?

A

Trigonal planar - 120

30
Q

What is a molecule called with 3 electron pairs and 1 lone pair?

A

Bent -118

31
Q

What is a molecule called with 4 electron pairs and no lone pairs?

A

Tetrahedral -109.5

32
Q

What is a molecule called with 4 electron pairs and 1 lone pair?

A

Trigonal pyramid -107

33
Q

What is a molecule called with 4 electron pairs and 2 lone pairs?

A

Bent - 104.5

34
Q

What is a molecule called with 5 electron pairs and no lone pairs?

A

Trigonal Bipyramid- 90 and 120

35
Q

What is a molecule called with 5 electron pairs and 1 lone pair?

A

Seesaw - 90 and 120

36
Q

What is a molecule called with 5 electron pairs and 2 lone pairs?

A

T-shaped- 89 and 120

37
Q

What is a molecule called with 6 electron pairs and no lone pairs?

A

Octahedral - 90

38
Q

What is a molecule called with 6 electron pairs and 1 lone pair?

A

Square based pyramid- 90

39
Q

What is a molecule called with 6 electron pairs and 2 lone pairs?

A

Square planar - 90

40
Q

What is electronegativity?

A

An atom’s ability to attract the electron pair in a covalent bond is called electronegativity

41
Q

When are polar bonds formed?

A

The bonding electrons will be pulled towards the atom with the greater electronegativity in a covalent bond. For atoms like carbon and hydrogen with really similar electronegativity, they are essentially non-polar when bonded together.

42
Q

What is a dipole and when are they formed?

A

A dipole is a difference in charge between the two atoms caused by a shift in electron density in the bond.

43
Q

What affects the polarity of a bond?

A

The greater the difference in electronegativity of two atoms- the more polar the bond

44
Q

How do molecules with permanent dipoles interact?

A

There will be weak electrostatic forces of attraction between the delta+ and delta- charges on neighboring molecules

45
Q

What are the three types of intermolecular forces?

A

1) Induced dipole-dipole or van der Waals forces
2) Permanent dipole-dipole forces
3) Hydrogen bonding
(IM forces affect the physical properties of a compound)

46
Q

What are Van der Waal forces?

A

They are found between all atoms and molecules
1) at any moment the elections in charge could be more likely to be on one side than the other- causing a temporary dipole
2) this dipole can cause another temporary dipole in the opposite direction of a neighboring atom and the two dipoles are then attracted together
3) it follows on like a domino effect
4) because the electrons are constantly moving dipoles are constantly created and destroyed

47
Q

What are Van der Waal attractions?

A

When molecules are held together in a lattice it is by weak van der Waals attractions

48
Q

What is the link between Van der Waals and boiling points?

A

1) Not all Van der Waals forces are the same strength- larger molecules have larger electron clouds, meaning stronger van der Waals forces.
2) The shape of molecules also affects the strength of the Van der Waal forces. Long, straight molecules can lie closer together than branched ones- the closer together the two molecules get, the stronger the forces between them are
3) When you boil a liquid, you need to overcome the intermolecular forces, so that the particles can escape from the liquid surface. It stands to reason that you need more energy to overcome stronger intermolecular forces, so liquids with stronger van der Waals forces will have higher boiling points

49
Q

When does hydrogen bonding occur?

A

It only happens when hydrogen is bonded to Nitrogen, fluorine, or oxygen as they are all very electronegative and it creates a polar bond with a high polarity.
Hydrogen has such a high charge density that the hydrogen atoms form weak bonds with lone pairs of electrons on the F N O of other molecules

50
Q

How does hydrogen bonding affect a substance’s boiling and melting points?

A

It increases it because of the extra energy needed to break the hydrogen bonds.

51
Q

Why is ice less dense than water (hydrogen bonds)?

A

As the liquid cools to form ice the molecules make more hydrogen bonds and arrange themselves into a regular lattice structure. In the structure the H2O molecules are further apart on average than the molecules in liquid water- so ice is less dense than liquid water.

52
Q

What structure do metal elements exist as?

A

Giant metallic lattice structures
The outermost shell of electrons in a metal is delocalized forming an ion in a sea of delocalized electrons. The pos metal ions are attracted to the neg sea of delocalized electrons. This is metallic bonding.

53
Q

Why do metals have high melting points?

A

Because of the strong electrostatic attraction between the positive metal ions and the sea of delocalized electrons which require lots of energy to break. The more delocalized electrons per atom the higher the melting point because the bonding will be stronger.

54
Q

Why are metals good thermal conductors?

A

The delocalized electrons can pass kinetic energy to each other, making it a good thermal conductor

55
Q

Why are metals good electrical conductors?

A

Metals are good electrical conductors because the delocalized electrons can move and carry a charge.

56
Q

Why are metals insoluble?

A

because the metallic bonds are too strong to break

57
Q

Why are metals malleable and alloys not?

A

In metals the layers of ions can easily slide over one another while in alloys the difference in size means they can’t

58
Q

What are the physical properties of a solid?

A
  • particles very close together
  • high density
  • incompressible
  • particles vibrate around a fixed point
59
Q

What are the physical properties of a liquid?

A
  • similar density to a solid
  • virtually incompressible
  • particles move about freely and randomly within the liquid, allowing it to flow
60
Q

What are the physical properties of a gas?

A
  • Particles have lots of energy
  • particles are further apart
  • low density
  • very compressible
  • particles move freely and quickly in all directions
  • will diffuse to fill a container
61
Q

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

A

As the 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.

62
Q

What should you look out for when drawing hydrogen bonds?

A

Show all lone pairs
Show all dipoles and all partial charges
Show hydrogen bond from lone pair to hydrogen atom

63
Q

What are AlCl3 dimers?

A

It is a giant ionic lattice
Aluminum metal completes its octet by forming a coordinate/dative bond with the chlorine atom of the other AlCl3 molecule.

64
Q

What are dimers?

A

The product of joining two molecular entities by bonds

65
Q

What scale is electronegativity measured in?

A

The Pauling scale

Chemistry (22 decks)

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