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Higher Chemistry > Bonding and Structure > Flashcards

Bonding and Structure Flashcards

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1
Q

what is metallic bonding

A

The attraction between positively charged ions in a sea of delocalised electrons

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2
Q

why can metals conduct electricity

A

The delocalised electrons are free to move in the solid lattice. These mobile electrons can act as charge carriers in the conduction of electricity or in the conduction of heat.

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3
Q

what happens to the strength of metallic bonding as you go across a period

A

bond strength increases

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4
Q

what happens to the strength of metallic bonding as you go down a group

A

bond strength decreases

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5
Q

why does metallic bond strength increase going across a period

A

The number of electrons in the outer shell increases, so the atoms are smaller, meaning of electrons are closer to the core

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6
Q

why does metallic bond strength decrease going down a group

A

The number of electron shells is increasing so atoms are larger mean in the electrons are further away

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7
Q

what does the increasing bond strength going across a period explain

A

the increasing melting and boiling points in metals going across a period

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8
Q

what does the decreasing bond strength going down a group explain

A

the decreasing melting and boiling pints in metals going down a group

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9
Q

what are the noble gases

A

single atoms (monatomic)

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10
Q

why is no value given for the atomic radii of the noble gases

A

because noble gases are unreactive, so don’t form bonds

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11
Q

what are intramolecular bonds

A

bonds within the molecule (covalent, ionic)

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12
Q

what are intermolecular bonds

A

bonds between the molecules (van der waals)

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13
Q

what types of intermolecular forces of attraction do non metals and monatomic gases contain

A

London Dispersion Forces (LDF’s)

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14
Q

what is a temporary dipole

A

when electrons in an atom become unevenly distributed

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15
Q

what happens to the strength of LDFs as the size of the atom increases

A

their strength increases

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16
Q

what happens to the boiling point of the noble gases as you go down the group

A

The boiling point increases as the size of the atom increases. This happens because the LDFs increase with increasing numbers of electrons. More electrons means bigger the dipole, so the stronger LDFs

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17
Q

what is the molecular formula of carbon

A

C60

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18
Q

what is the molecular formula of sulfur

A

S8

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19
Q

what is the molecular formula of phosphorous

A

P4

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20
Q

what is the boiling point of covalent molecular substances described to be

A

low

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21
Q

what bonding exists within covalent molecular substances

A

strong covalent

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22
Q

what bonding exists between the molecules of covalent molecular substances

A

intermolecular forces

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23
Q

why is the melting/boiling point of covalent molecular substances so low

A

because only very weak LDFs/intermolecular forces exist between the particles and these require little energy to break. resulting in low, melting and boiling points.

24
Q

what bonds do the halogens contain

A

strong intramolecular forces (covalent bonds) but weak intermolecular forces

25
Q

why do the halogens have low melting and boiling points

A

the weak intermolecular forces are easily overcome

26
Q

what happens to the boiling point of the halogens as you go down the group

A

the boiling point increases

27
Q

why does the boiling point of the halogens increase as you go down the group

A

As a size of the halogen atom increases, there is a greater number of electrons this means a greater number of LDFs between the molecules. The more LDFs present the more energy required to break them.

28
Q

what are fullerenes

A

a form of Carbon exist as covalent molecules, are a large family of carbon cage molecules, each made up of rings of carbon atoms.

29
Q

elements that exist as covalent networks

A

Carbon (diamond, graphite)
Boron
Silicon

30
Q

what is a polymorph

A

Different forms of the same element, for example, carbon in the form of diamond and graphite

31
Q

why does diamond not conduct

A

Because all of the four of the electrons on the carbon atoms are used in the bonding, so there are no delocalised electrons

32
Q

why does graphite conduct

A

because only three outer electrons in the carbon atom are used in bonding so each carbon atom has one outer electron not used in bonding. These electrons are delocalised so graphite can conduct

33
Q

why is diamond so difficult to break

A

The bonds around each carbon atom are in a tetrahedral shape (3D) this makes diamond strong. To cut a break, diamond means breaking laws of covalent bonds (intramolecular) This requires a lot of energy so it is difficult to break

34
Q

why is graphite brittle

A

The bonds within graphite are arranged in layers between the layers are very weak LDFs. To cut our break time and means breaking the weak LDFs so it is easier to cut or break.

35
Q

what elements exits as solid covalent molecular

A

sulphur and phosphorus

36
Q

what elements exists as covalent networks

A

Carbon in the forms of diamond and graphite, boron and silicon

37
Q

what is ionic bonding

A

The attraction between positive and negative ions

38
Q

what is covalent bonding

A

The attraction of the shared electrons for the nuclei of both the bonded atoms

39
Q

why do ionic compounds have high melting and boiling points

A

because separating the ions in the lattice, involves the breaking of strong ionic bonds (intramolecular) which means high melting points

40
Q

why do covalent molecular solids have low melting points

A

Because separating molecules involved little energy as they’re only weak intermolecular forces between the molecules

41
Q

why do covalent network compounds have high melting points

A

Because melting them involves breaking the network of strong covalent bonds (intramolecular), which means lots of energy is required

42
Q

what is electronegativity

A

A measure of the attraction an atom involved in a bond has for the electrons in a bond

43
Q

what happens to electronegativity as you move along a period

A

it increases

44
Q

what happens to electronegativity as you go down group

A

It decreases

45
Q

why does electronegativity increase going across the period

A

going across the period, the nuclear charge increases this pulls the electron shell closer to the nucleus as a result, the electronegativity increases

46
Q

why does the electronegativity decrease as you go down group

A

because going to the group, the nuclear charge increases the number of electron shells also increases as a result of shielding and an increase in distance between the outer shell of electrons and the nucleus, electronegativity decreases

47
Q

what is a non polar covalent bond

A

where within a bond the electrons are equally shared due to the same electronegativity values.

48
Q

what is a polar covalent bond

A

A bond between two different atoms where the electrons are not shared equally, the electrons in the bond will be closer to the more electronegative atom, due to the difference in electronegativity. This produces a permanent dipole between molecules in an atom.

49
Q

what does a greater difference in electronegativity mean

A

The greater the difference in electronegativity, the more polar the bond will be

50
Q

why is CCl4 non polar

A

within this molecule there is polar bonding, but it is not a polar molecule. This is because they have a negative charges at both ends of the nucleus, so it is a nonpolar molecule as the charges are symmetrical.

51
Q

how do molecules with a permanent dipole attract each other?

A

through dipole-dipole interactions, these are stronger than LDFs

52
Q

why are the boiling points of NH3, H20 and H2F higher then expected

A

Because they contain hydrogen bonding

53
Q

what is hydrogen bonding

A

It’s a special type of dipole-dipole interaction that occurs in compounds, which of hydrogen atoms bonded to very electronegative elements such as N, O, and F. Hydrogen bonds are stronger than LDFs and permanent dipoles but weaker than covalent and ionic bonds

54
Q

what does hydrogen bonding cause

A

It causes melting and boiling points and viscosity of a chemical to be higher than expected

55
Q

what is viscosity

A

Viscosity is a measure of a thickness

56
Q

what does high viscosity mean

A

High viscosity means strong, intermolecular forces are present

57
Q

what does ‘Like Dissolves Like’ mean

A

it means that polar an ionic substances tend to dissolve in polar solvents, so a nonpolar substance will not dissolve in a polar solvent only in a non polar solvent. For example, water is able to dissolve sodium chloride as they are both polar molecules.

Higher Chemistry (7 decks)

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