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Higher Chemistry > UNIT 1 > Flashcards

UNIT 1 Flashcards

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1
Q

idescribe the trend in covalent radii when moving from left to right across the periodic table

A

as you move across periods the atoms get smaller

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2
Q

explain the trend in covalent radii when moving from left to right across the periodic table

A

bigger nuclear charge due to more protons, this pulls electron shells closer and therefore covalent radii is smaller

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3
Q

describe the trend in covalent radii when moving down groups.

A

as you move down a group the size of atoms get bigger

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4
Q

explain the trend in covalent radii when moving down groups.

A

atoms get bigger as you go down a group as extra shells of electrons are shielded from nuclear charge by inner shells of electrons. as you move down a group shielding increases

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5
Q

explain the difference in size between atoms that are on opposite sides of the periodic table?

A

the atom on the left is bigger due to the smaller number of protons it possesses. the atom on the right is smaller due to the bigger number of protons it possesses which leads to an increased nuclear charge, the increased nuclear charge pulls electron shells closer together hence the smaller size.

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6
Q

what is meant by ionisation energy?

A

energy required to remove 1 mol of electrons from the outer shell of one mol of atoms in a gaseous state

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7
Q

is ionisation energy exothermic or endothermic?

A

endothermic as it requires input of energy as energy is needed to strip electrons away

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8
Q

explain why the second ionisation energy of an alkali metal is bigger than that of the halogen in the same period

A

in alkali metals, the second electron is removed from a shell closer to the nucleus in alkali metals. this means that it is more exposed and requires more energy

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9
Q

why is there no fourth ionisation energy of lithium?

A

as lithium only has 3 electrons

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10
Q

which 3 elements have the lowest ionisation energy and why?

A

Li, Na and K have the lowest ionisation energy as they have the smallest nuclear charge in each period (so largest atoms) that means electrons are not so tightly held so take less energy to remove

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11
Q

which two elements have the highest ionisation energy and why?

A

He and Ne as they are in group 0 and have the biggest nuclear charge (smallest atom in period.) meaning that electrons are held tighter and take more energy to remove

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12
Q

what is the trend in electronegativity when moving from left to right across the periodic table?

A

electronegativity increases as increased nuclear charge so stronger attraction for bonding electron. this pulls the bonding electron closer

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13
Q

what is the trend in electronegativity when moving down a group?

A

electronegativity decreases as shielding increases. extra shells of electrons shield bonding e- from nuclear charge so weaker attraction

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14
Q

explain the difference in electronegativity between two atoms in the same period? (e.g lithium and fluorine)

A

Li (closer to left) is smaller in terms of electronegativity as it has a smaller nuclear charge and F (closer to right) is bigger in terms of electronegativity as it has a larger nuclear charge.

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15
Q

what is a covalent bond?

A

a covalent bond is a result of two positive nuclei being held together by the common attraction for the shared pair of negative electrons.

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16
Q

in a covalent bond what is shared?

A

in a covalent bond the atoms share a pair of electrons

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17
Q

how are polar covalent bonds formed?

A

polar covalent bonds are formed when the attraction for the bonding pair of electrons is different

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18
Q

explain how hydrogen chloride is an example of polar bonding

A

Chloride has a higher electronegativity and therefore pulls the shared pair of electron closer to it. this creates the partial change which forms a dipole

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19
Q

what are the properties of diamond?

A

covalent network
high melting/boiling point
doesnt conduct electricity

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20
Q

what are the graphites properties?

A

covalent network
high melting/boiling point
can conduct electricity because of free e^1

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21
Q

what are the properties of fullerine?

A

covalent molecules

lower mp/bp

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22
Q

what is ionic bonding?

A

the movement of bonding electron from an atom with low electronegativity to an atom with high electronegativity is complete = > ions are formed

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23
Q

how to tell if a molecule is polar?

A

if it contains non symmetrical bonds and has polar bonds

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24
Q

how to tell if a molecule is non-polar?

A

it contains non-polar bonds

contains polar bonds but arranged symmetrically

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25
Q

what do the van der waals interactions do?

A

these allow all molecular elements and compounds (and monatomic elements) to change state

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26
Q

what are the three types of van der waal interactions?

A

london dispersion forces
permanent dipole - PDI - PDI
Hydrogen bonding

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27
Q

which WDV force is the weakest?

A

london dispersion forces

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28
Q

how are london dispersion forces formed?

A

they are formed due to electrostatic attractions between temporary and induced dipoles which form due to the movement of electrons in atoms and molecules

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29
Q

what does the strength of london dispersion forces depend on?

A

the force of LDF is related to the number of electrons within the atom/molecule.

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30
Q

how is a temporary dipole formed?

A

if the electrons are on the same side of the atom at the same time, this forms a temporary dipole

31
Q

how are induced dipoles formed?

A

temporary dipoles can cause induced dipoles in adjacent atoms as the negatively charged electrons of one atom repels the similarly charged electrons of the other atom

32
Q

what are PD-PDI interactions?

A

an intermolecular force between polar molecules. it is stronger than LDF but weaker than H bonding

this is when polar molecules display attractions between the oppositely charged ends of the molecules.

33
Q

what are hydrogen bonds?

A

these are the strongest van der waal force (but weaker than covalent bonds) and are a type of PD-PDI. a bond is only a hydrogen bond if hydrogen and N O F are bonded

34
Q

electronegativity of hydrogen and what does this mean?

A

hydrogen has very low electronegativity and N O F have very high electronegativity that means that these bonds will be highly polar

35
Q

how do you tell if a molecule is LDF?

A

if the molecule is non polar and not a metal or covalent - usually elements

36
Q

what does it mean for LDF reaction if the number of electrons increase?

A

Generally, as number of electrons increases, strength of LDF increases

37
Q

how do hydrogen bonds affect boiling points?

A

more hydrogen bonds between molecules

leads to an increase in viscosity and increased boiling point/melting point.

38
Q

are boiling/melting points higher for polar or non-polar molecules?

A

boiling point of polar substances are higher than non-polar substances with a similar number of electrons because of the stronger intermolecular forces in polar substances PD-PDI and H bonding in polar substances.

39
Q

how does viscosity work？

A

as molecule size increases, viscosity increases

40
Q

solubility of polar and non-polar elements?

A

Polar molecules are usually soluble in Polar solvents. So polar molecules and ionic substances are usually soluble in water. While non-polar molecules are usually soluble in non-polar substances.

41
Q

what is water used as?

A

H20 - polar solvant

42
Q

density of water?

A

ice is less dense than water due to hydrogen bonding. More stable hydrogen bonds in solid ice but there is fewer hydrogen bonds in liquid water

ice holds hydrogen bonds a certain distance apart.

43
Q

miscibility meaning?

A

Miscibility is the ability for two liquids to mix together

44
Q

miscibility in polar/non-polar substances

A

· Polar liquids are normally miscible with each other (alcohol and water)

· Non-polar liquids are immiscible with polar liquids (oil and water)

45
Q

properties of group one

A

alkili metals

  • One electron in the outside shell
  • Form a 1+ ion by losing 1 electron
  • React with water to form hydrogen gas and make the water alkali
  • Reactivity increases as we move down a group
46
Q

properties of group two

A

alkali earth metals

  • Two electrons in the outside shell
  • Form a 2+ ion by losing 2 electrons
  • React with water but not as reactive as group 1
  • Reactivity increases as we move down the group
47
Q

what is electronegativity?

A

A measure of attraction an atom has to its bonding electrons

48
Q

properties of metallic bonding?

A

. Only occurs in metal elements

· Strong – takes a lot of energy to break

· Positive ions in a ‘sea of delocalised electrons’

  • an electrostatic force of attraction between the positive metal ions and the negative delocalised electrons.
49
Q

properties of covalent bonding?

A

· Non- polar

· Occurs in diatomic gases, covalent molecular and covalent network molecules

· (two) positive nuclei sharing a pair of electrons

50
Q

delocalised electrons are…?

A

delocalised electrons are free to move around

51
Q

structure of metal?

A

metallic lattice

52
Q

structure of covalent network?

A

giant covalent lattices (covalently bonded together)

53
Q

what type of force occurs between diatomic gasses?

A

diatomic molecules held together by London dispersion forces. they are covalent molecular

54
Q

structure of monotomic gasses?

A

non-bonding, unreactive gases, individual atoms joined by weak London dispersion forces.

they are stable atoms. They have fuller outer energy levels so they do not usually form molecules with other atoms

They have low melting and boiling points as they are easily separated by overcoming the weak forces of attraction between the atoms.

55
Q

what type of bonding occurs in covalent molecular solids?

A

discrete covalently bonded molecules held by weak London dispersion forces

56
Q

properties of polar covalent bonds?

A

· Polar covalent bonds are formed when the attraction for the bonding pair of electrons is different

  • a bond is polar if they have a reasonable difference in electronegativity (0.5 or more)
57
Q

what is a reducing agent?

A

A substance that is itself oxidised causing another substance to be reduced.It is an electron donor

58
Q

what is an oxidising agent?

A

A substance that is itself reduced causing another substance to be oxidised.It is an electron acceptor

59
Q

where in the data booklet will you find strong oxidising agents?

A

The strongest oxidising agents are at the bottom of the left-hand column of the electrochemical series

60
Q

where on the data booklet will you find strong reducing agents?

A

The strongest reducing agents are at the top of the right-hand column of the electrochemical series

61
Q

if an element is highly electronegative it is an _____

A

an oxidisng agent

62
Q

in a redox equation what is cancelled out?

A

electrons

63
Q

what is a discrete molecule?

A

Discrete covalent molecules are small groups of atoms held together by strong covalent bonds inside the molecule and weak intermolecular forces between the molecules.

64
Q

what are properties of a covalent network?

A
  • contains carbon diamond, carbon graphite, boron and silicon
  • have very high melting/boiling points as energy is needed to overcome strong covalent bonds
  • layers are attached to each other by LDF
  • only graphite can conduct electricity due to delocalised electrons
65
Q

properties of covalent molecular?

A
  • small electrons attracted to each other through LDF
  • has lower mp/bp than covalent networks and metals due to weak LDF
  • contains carbon fullerene, sulphur, diatomic molecules/the halogens and phosphorus
66
Q

properties of monatomic?

A
  • noble gasses

- solid and liquid noble gases are formed when the atoms are attracted to neighbouring atoms through LDF

67
Q

bonding continuum

A

ionic covalent pure covalent
< ———————————————————->
larger diff in a small difference
electronegativity. in electronegativity

68
Q

how are ions formed?

A

they are formed by an atom losing electrons and another gaining electrons

69
Q

ionic lattice

A

a giant structure consisting of thousands of oppositely charged ions

70
Q

qualities of ionic compounds?

A
  • high mp/bp as lots of energy is needed to break the strong ionic bonds
  • non-conductors as solid but can be as liquid as ions are free to move
  • soluble in polar substances because ionic compounds breakdown into charged ions when added to the solvent
71
Q

qualities of polar covalent compounds?

A
  • mp/bp = ionic > polar > non-polar
  • non-conductors
  • soluble in polar substances
72
Q

qualities of non-polar covalent compounds?

A
  • low mp/bp due to weak LDF
  • non-conductors
  • soluble in non-polar substances
73
Q

where can polar and non-polar bonds exist?

A

in covalent bonds

74
Q

how are ions formed?

A

by losing/gaining electrons

Higher Chemistry (3 decks)

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