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Chemistry > AS - Bonding > Flashcards

AS - Bonding Flashcards

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1
Q

What do you get when different elements bond together?

A

A compound.

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2
Q

What is ionic bonding?

A

Electrostatic attraction between oppositely charged ions in a lattice.

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3
Q

What are the simplest ions?

A

Single atoms that have either gained or lost electrons to achieve a full outer shell of electrons.

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4
Q

What are compound ions?

A

Ions made up of groups of atoms with an overall charge.

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5
Q

What are the formulas for the following compound ions:

  1. Sulfate ion
  2. Hydroxide ion
  3. Nitrate ion
  4. Carbonate ion
  5. Ammonium ion?
A

Sulfate - SO4^2-

Hydroxide - OH-

Nítrate - NO3-

Carbonate - CO3^2-

Ammonium - NH4+

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6
Q

What is the overall charge of any compound?

A

0

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7
Q

What are ionic crystals?

What is a lattice?

A

Giant lattices of ions.

A lattice is a regular structure.

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8
Q

What type of structure does sodium chloride have? Describe this.

A

A giant ionic lattice structure. Where the Na+ and Cl- ions altérnate in a cube shaped lattice.

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9
Q

What does the structure of ionic compounds determine?

A

Their physical properties.

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10
Q

Explain the conductivity, solubility and melting points of ionic compounds.

A
  1. They conduct electricity when they’re molten or dissolved but not when they’re solid:
    The ions in a liquid are free to move and carry a charge but in a solid, ions are fixed in place by strong ionic bonds.
  2. High melting points:
    Giant ionic lattices are held together by strong electrostatic forces. It takes lots of energy to overcome these forces.
  3. Tend to dissolve in water:
    Water molecules are polar so the positive and negatively charged ions in the lattice can be pulled away by the polarity of water.
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11
Q

What are molecules?

A

Two or more atoms bonded together.

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12
Q

When does covalent bonding occur?

A

Between non-metals in a molecule.

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13
Q

What is a single covalent bond?

A

A shared pair of electrons between two atoms.

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14
Q

What do multiple covalent bonds contain?

A

Multiple pairs of electrons.

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15
Q

What is another name for a giant covalent structure?

A

A macro molecular structure.

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16
Q

Why can carbon atoms form macromolecular structures?

A

Because each carbon atom can form four strong, covalent bonds.

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17
Q

Describe and explain the structure of graphite.

A

Carbon atoms are arranged in sheets of flat hexagons covalently bonded with three bonds each. The fourth outer electron of each carbon atom is delocalised and found between the hexagonal sheets.

The sheets of hexagons are bonded together by weak van der Waals forces.

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18
Q

State and explain the properties of graphite and how these are related to its structure.

A
  1. Weak bonds between the layers in graphite are easily broken so the sheets can slide over each other - used as a dry lubricant/in pencils.
  2. Can conduct electricity as the delocalised electrons are free to move and carry a charge.
  3. Very high melting point due to the strong covalent bonds.
  4. Insoluble in any solvent. As covalent bonds in sheets are too strong to break.
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19
Q

Describe the structure of diamond.

A

Made up of carbon atoms, each covalently bonded to four other carbon atoms. The atoms arranged themselves in a tetrahedral shape. It is a macromolecular structure.

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20
Q

State and explain the properties of diamond, related to its structure.

A
  1. Very high melting point due to strong covalent bonds.
  2. Extremely hard due to covalent bonds.
  3. Good thermal conductor as vibrations easily travel through stiff lattice.
  4. Can’t conduct electricity as all electrons are held in localised bonds.
  5. Won’t dissolve in any solvent due to covalent bonds.
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21
Q

What is another name for a co-ordinate bond?

A

Dative covalent bond.

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22
Q

What is a co-ordinate bond?

A

Contains a shared pair of electrons with both electrons supplied by one atom.

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23
Q

How is a co-ordinate bond represented?

A

Using an arrow, point away from the donor atom.

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24
Q

Describe and explain metallic bonding.

A

Involves attraction between delocalised electrons and positive ions arranged in a giant metallic lattice.

The outermost shell of electrons of a metal atom is delocalised so the electrons are free to move about the metal.

The positive metal ions are attracted to the delocalised negative electrons. They form a lattice of closely packed positive ions in a sea of delocalised electrons.

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25
Q

State and explain the properties of metals, related to their structure.

A
  1. High melting points because of the strong electrostatic attraction between positive metals and the delocalised sea of electrons.
  2. Number of delocalised electrons per atom affects the melting point. The more there are, the stronger the bonding will be and higher the melting point.
  3. Good electrical conductors as delocalised electrons can move and carry charge.
  4. Insoluble due to strength of metallic bonds.
26
Q

Explain the structure of iodine.

A

Simple covalent/molecular where atoms of iodine are covalently bonded together but there are only weak VDWs forces between the molecules.

27
Q

Explain the properties of iodine related to its structure.

A
  1. Low melting point as this involves breaking weak intermolecular forces, not the covalent bonds.
  2. Does not conduct electricity as electrons are not free to move and carry a charge.
28
Q

Describe hydrogen bonding and explain when it occurs.

A

Only occurs when hydrogen is covalently bonded to fluorine, nitrogen or oxygen.

F, N and O are all very electronegative, so they draw bonding electrons away from the H atom. The bond is so polarised, and hydrogen has such a high charge density (because it’s so small) that the hydrogen atoms form weak bonds with lone pairs of electrons on the F, N, or O atoms of other molecules.

29
Q

Explain the structure of ice and how this relates to its density.

A

As liquid water cools to form ice, the molecules make more hydrogen bonds and arrange themselves into a regular lattice structure. In this structure, the H2O molecules are further apart than the molecules in liquid water.

So ice is less dense than liquid water.

30
Q

What does molecular shape depend on?

A

The number of pairs of electrons in the outer shell of the central atom.

31
Q

What are bonding pairs of electrons?

A

These are pairs of electrons shared between two atoms in a covalent bond.

32
Q

What is a lone pair of electrons?

A

A pair of electrons which are not shared.

33
Q

Bonding pairs and lone pairs of electrons exist as charge clouds. What are charge clouds?

A

An area with a high chance or finding an electron pair (electrons are always moving).

34
Q

How do pairs of electrons in the outer shell of atoms arrange themselves and why?

A

As far apart as possible to minimise repulsion.

35
Q

Which repels more, a lone or bonding pair of electrons?

A

A lone pair of electrons.

36
Q

State which type of bonding has the greatest angle, to the type of bonding with the smallest angle.

A

Lone-pair/lone-pair angles are the biggest.

Lone-pair/bonding-pair angles are the second biggest.

Bonding-pair/bonding-pair angles are the smallest.

37
Q

Outline the steps used to predict the shape of a molecule, including if you’re dealing with an ion.

A
  1. Work out which is the central atom (the atoms that all the other atoms are bonded to).
  2. Use the periodic table to work out the number of electrons in the outer shell of the central atom.
  3. Add one to this number for every atom that the central atom is bonded to. (If dealing with an ion, then add 1 for each negative charge on the ion or subtract 1 for each positive charge).
  4. Divide by 2 to find the number of electron pairs on the central atom.
  5. Compare the number of electron pairs to the number of bonds to find the number of lone and bonding pairs on the central atom.
38
Q

What is the bond angle and name of the angle with a molecule with two electron pairs and no lone pairs of electrons.

A

Linear.

180 degrees.

39
Q

What is the bond angle and name of this for a molecule with three electron pairs and no lone pairs?

A

Trigonal planar.

120 degrees.

40
Q

What is the bond angle and name of this for a molecule with 4 electron pairs but no lone pairs?

A

Tetrahedral.

109.5 degrees.

41
Q

What is the bond angle and name of this for a molecule with three bonding pairs and one lone pair of electrons?

A

Trigonal pyramidal.

107 degrees.

42
Q

What is the bond angle and name of this for a molecule with 2 bonding and 2 lone pairs of electrons?

A

Bent.

104.5 degrees.

43
Q

What are the bond angles and name of this type for a molecules with five electron pairs and no lone pairs?

A

Trigonal bipyramidal.

90 and 120 degrees.

44
Q

What are the bond angles and name of this type for a molecule with four bonding pairs and one lone pair of electrons?

A

Seesaw.

87 and 102 degrees.

45
Q

What is the bond angle and name of this for a molecule with three bonding and two lone pairs of electrons?

A

T-shaped.

88 degrees.

46
Q

What is the bond angle and name of this for a molecule with six bonding and no lone pairs of electrons?

A

Octahedral.

90 degrees.

47
Q

What is the bond angle and name of this type for a molecule with four bonding and two lone pairs of electrons?

A

Square planar.

90 degrees.

48
Q

What is electronegativity?

A

The power of an atom to attract the pair of electrons in a covalent bond.

49
Q

What will the electron distribution in a covalent bond be between elements with different electronegativities? What does this produce?

A

Unsymmetrical.

This produces a polar covalent bond and may cause the molecule to have a permanent dipole.

50
Q

What is the most electronegative element?

A

Fluorine.

51
Q

Why is a covalent bond between two atoms of the same element non-polar?

A

Because the atoms have equal electronegativities so the electrons are equally attracted to both nuclei.

52
Q

What is a dipole?

A

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

53
Q

The greater the difference in electronegativity, the ____ _____ the bond.

A

More polar.

54
Q

Are intermolecular forces stronger or weaker than covalent, ionic or metallic bonds?

A

Much weaker.

55
Q

What are the three types of intermolecular forces I need to know?

A
  1. Induced dipole-dipole or VDWs forces
  2. Permanent dipole-dipole forces
  3. Hydrogen bonding
56
Q

When are VDWs forces present?

A

They are found between all atoms and molecules.

57
Q

What physical state is iodine at room temperature?

A

Solid.

58
Q

Describe VDWs forces and how they occur.

A

Electrons in charge clouds are always moving very fast. At any moment, the electrons are likely to be more to one side than the other. At this moment, the atom has a temporary dipole.

This dipole can cause another temporary dipole in the opposite direction of a neighbouring atom, and so on with the next atom. The dipoles are attracted to each other at that instant.

These dipoles are being created and destroyed all the time as electrons are constantly moving. But the overall effect is for the atoms to be attracted to one another.

59
Q

What affects the strength of VDWs forces?

A

Larger molecules have larger electron clouds so stronger VDWs.

The shape of molecules - long, straight molecules can lie closer together than branched molecules so have stronger VDWs.

60
Q

Why do liquids with stronger VDWs forces have higher boiling points?

A

Because when you boil a liquid, you have to overcome the intermolecular forces so that particles can escape from the liquid surface. You need more energy to overcome stronger intermolecular forces.

Chemistry (34 decks)

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