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CHEM 2.0 > Atomic structure, the periodic table, bonding, properties of matter > Flashcards

Atomic structure, the periodic table, bonding, properties of matter Flashcards

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1
Q

what is a chemical bond?

A

a force of attraction

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2
Q

describe a covalent bond

A

pair of electrons are shared between non-metal atoms to gain full outer shells

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3
Q

what is the IMF between molecules in simple covalent substances?

A

weak

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4
Q

what is the usual state of simple covalent substances and why?

A

gases and liquids - IMF broken in state change

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5
Q

what is the BP of simple covalent substances?

A

low BP

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6
Q

what is the charge of simple covalent substances?

A

neutral charge (doesn’t conduct electricity)

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7
Q

what is the formula type used for simple covalent substances?

A

molecular

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8
Q

a bigger molecule has what type of IMF and MP?

A

stronger intermolecular forces - higher melting point

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9
Q

what is the state of giant covalent substances?

A

solids

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10
Q

what is the MP of giant covalent substances?

A

very high melting point

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11
Q

what is the atomic structure of giant covalent substances?

A

all atoms bonded to others by strong covalent bonds which must be overcome to boil/melt these substances

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12
Q

what is the formula type of giant covalent substances?

A

empirical

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13
Q

describe a metallic bond

A
  • atoms in metals are tightly packed in layers - giant 3D lattices
  • outer electron(s) from each atom is delocalised & is able to move through the structure
  • each metal ions is equally attracted to delocalised electrons by electrostatic forces of attraction
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14
Q

describe an ionic bond

A
  • metals react with non-metals
  • electrons are transferred from the outer shell of metal atoms to the non-metal atoms, to get a full valence shell
  • strong electrostatic force of attraction between oppositely charged ions
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15
Q

what are the properties of ionic substances?

A
  • high melting points as there are strong forces between ions - lots of energy needed to break/overcome them
  • solid at room temperature
  • do not conduct electricity as solids
  • conduct electricity when molten or in solution - as solid, ions in fixed positions and cannot move so cannot carry charge. when molten/dissolved, ions free to move & can carry charge
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16
Q

describe the structure of ionic compounds when dissolved in water

A

water causes the giant lattices to break apart so ions become individual and are free to move.

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17
Q

what are ions?

A

electrically charged particles with a different number of protons and electrons

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18
Q

why do metals form positive ions?

A

it is easy for them to lose electrons as they have a small number of electrons in the valence shell

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19
Q

what does ion charge correspond to?

A

group number (for 1=1+ 2=2+ 3=3+ 5=3- 6=2- 7=1-)

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20
Q

what is a pro of the dot-cross diagram?

A

shows the electron structure of the ions

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21
Q

what is a con of dot-cross diagram?

A

can give the impression that the structure is made of pairs of ions, rather than being a continuous structure containing a massive number of ions

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22
Q

what is a pro of the ball and stick structure?

A

helps to show how ions are arranged relative to each other

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23
Q

what are some cons of the ball and stick structure?

A
  • the lines connecting ions may be confused with covalent bonds
  • it may be thought that ions are far apart from each other
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24
Q

what is pro of the 3D space filling structure?

A

gives a very good representation to how ions are packed together

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25
Q

what is a con of the 3D space filling structure?

A

can give the impression that the structure is limited to a few ions rather than being a continuous structure containing a massive number of ions

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26
Q

what is a pro of the 2D space filling structure?

A

very easy to draw

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27
Q

what is a con of the 2D space filling structure?

A
  • only shows the structure in 2D but the lattice is really 3D
  • can give the impression that the structure is made of pairs of ions, rather than being a continuous structure containing a massive number of ions
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28
Q

what are the features of a solid?

A
  • forces of attraction between particles are strong so particles are held in fixed positions (they do vibrate)
  • particles do not move from fixed positions so keep a definite shape and volume
  • the hotter they get the more they vibrate so solids expand slightly when heated
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29
Q

what are the features of a liquid?

A
  • forces of attraction between particles are weak so particles are held close together but are in random positions and move
  • definite volume but not shape
  • particles move with random motion
  • the hotter they get the faster they move so liquids expand slightly when heated
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30
Q

what are the features of a gas?

A
  • forces of attraction between particles are very weak
  • particles travel in straight lines until something changes their direction so will spread out
  • do not keep definite volume or shape
  • will expand to fill whatever container they are in.
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31
Q

describe the bonding in silicon dioxide

A
  • strong covalent bonds between O and Si atoms
  • each Si bonded to 4 O atoms
32
Q

describe the bonding in diamond and carbon

A
  • strong covalent bonds between all atoms (diamond, each is bonded to 4 others, graphite each is bonded to 3)
  • both are giant covalent (graphite is in layers [malleable, as layers slide])
  • very high M/BP due to strong covalent bonds
  • graphite conducts electricity (each atom has spare delocalised electron, forms electron cloud, free to move throughout structure)
33
Q

describe the structure of pure metals

A

arranged in layers - slide over each other - malleable

34
Q

describe the conductivity of metals

A

good - delocalised electrons carry charge throughout structure

35
Q

what is an alloy?

A

mixture of metals

36
Q

why are alloys harder than pure metals?

A

atoms are different sizes which distorts regular lattice structure so layers cannot slide

37
Q

what is the structure of graphene?

A

a single layer of graphite (1 atom thick)

38
Q

what are the properties of graphene?

A

excellent conductor of electricity (delocalised electrons) and extremely strong

39
Q

why is graphene strong?

A

each carbon atom is strongly bonded to 3 other carbon atoms by covalent bonds which require a lot of energy to overcome

40
Q

what is the structure of buckminster fullerene

A

60 carbon atoms arranged in a hollow sphere - these form rings with 5 or 6 carbon atoms

41
Q

describe the structure of fullerenes

A

molecules with hollow shapes, hexagonal rings of carbon atoms (can also be rings with 5 or 7 carbon atoms)

42
Q

what are some uses of fullerenes?

A

pharmaceutical delivery, lubricants, catalysts

43
Q

What are the features of carbon nanotubes?

A

high tensile strength and excellent conductors of heat and electricity

44
Q

what does ‘nano’ mean?

A

1 * 10^-9

45
Q

What are 3 applications of nanoscience?

A
  • antibacterial bandages & surfaces using silver nanoparticles to inhibit microorganism growth
  • gold nanocages; used for drug delivery to specific sites in the body
  • carbon nanotubes; reinforce materials used for sports; more durable and water resistant
46
Q

what are the features of nanoparticles?

A
  • made of a few hundred atoms
  • huge sa:v ratios so properties are different to behaviour on a large scale
  • smaller quantities of nanoparticles are needed to be effective than materials with normal particles sizes due to high SA:V ratio
47
Q

what is a risk of nanoparticles?

A

breathing them in may damage lungs

48
Q

what was JJ Thomson’s model of the atom?

A
  • plum pudding model
  • ball of positive charge with negative electrons embedded in it
49
Q

what happened in the alpha particle experiment?

A
  • positive alpha particles fired at thin piece of gold
  • most went through but some were deflected
  • suggested the positive charge of an atom is confined in a small volume (nucleus)
50
Q

in the gold alpha particle experiment, why did most alpha particles pass straight through gold atoms?

A

the atoms are not solid - mostly empty space

51
Q

in the gold alpha particle experiment, why did most alpha particles pass straight through gold atoms?

A

some come into contact with the nucleus which is positively charged, so is deflected - same charges repel

52
Q

what was Bohr’s adaptation to the model of the atom?

A

suggested electrons orbit nucleus at specific distances

53
Q

what was Chadwick’s adaptation of the model of the atom?

A

suggested the nucleus also contained neutral particles

54
Q

what are two key differences between thomson’s plum pudding model and rutherford’s replacement?

A

electrons in fixed orbit - shows protons in nucleus vs being a positive mass

55
Q

what is atomic number?

A

total protons in an atom

56
Q

what is mass number?

A

total protons and neutrons (bigger number)

57
Q

what is the empirical formula?

A

simplest ratio of atoms in a compound

58
Q

what is the molecular formula?

A

actual number of atoms in a compound

59
Q

what is an allotrope?

A

the atoms of the same element are bound to each other in different ways - the spatial arrangement of atoms is different

60
Q

what is an isotope?

A

members of a family of an element that all have the same number of protons but different numbers of neutrons

61
Q

what is group 0?

A

noble gases

62
Q

what are the properties of the noble gases?

A
  • chemically inert, as have stable electron configurations (full outer shells)
  • low density
  • non-flammable
  • generally low boiling point which increases down the group (as the atoms become larger so IMF become stronger, more energy is needed to overcome them)
  • exist as single atoms
63
Q

what is group 1?

A

alkali metals

64
Q

what are the properties of the alkali metals?

A
  • low density
  • very reactive (1 valence electron)
  • react with non-metals to form ionic compounds
  • form compounds that are white solids
  • dissolve in water to form colourless solutions
  • become more reactive down group (outer shell further away from nucleus - weaker attraction)
65
Q

what is group 7?

A

halogens

66
Q

what are the properties of the halogens?

A
  • non-metals
  • diatomic molecules
  • react with metals to form ionic compounds
  • form molecular compounds with other non-metals
  • form hydrogen halides
  • less reactive going down group (outer shell is further from nucleus - electron gained less easily)
  • melting and boiling points increase going down (as the atoms become larger so IMF become stronger, more energy is needed to overcome them)
67
Q

what are the properties of the transition metals?

A
  • good conductors of heat and electricity
  • can be hammered or bent into shape easily
  • high melting points (but mercury is a liquid at room temperature)
  • usually hard and tough
  • high densities
68
Q

Gallium was discovered six years after Mendeleev published his periodic table. Give two reasons why the discovery of gallium helped Mendeleev’s periodic table to become accepted.

A
  1. it fitted in a gap Mendeleev had left
  2. its properties were predicted correctly by Mendeleev
69
Q

compare group 1 and transition metal properties

A
  • group 1 metals have lower mp/bp and densities, are more reactive, always form 1+ ions and white compounds, and react with water and oxygen
  • transition metals have higher mp/bp and densities, are unreactive, form ions with different charges and coloured compounds, and are used as catalysts
70
Q

NaCl is solid at RT with a high mp/bp whereas Cl2 is a gas at RT. Explain the difference in properties

A
  • NaCl is an ionic lattice with strong electrostatic forces of attraction between each ion which require lots of energy to overcome
  • Cl2 is a small molecule with weak IMF which do not require much energy to overcome
71
Q

which 3 of the following substances have weak IMF?: CO2, CH4, graphite, graphene, diamond, O2

A

CO2, O2, CH4

72
Q

Suggest one limitation of using a dot and cross diagram and one limitation of using a 3D diagram.

A

dot and cross diagram only shows how electrons are arranged and 3D diagram only shows the arrangement of ions in space

73
Q

what was john dalton’s model of the atom?

A

tiny spheres that could not be divide

74
Q

what was ernest rutherford’s model of the atom?

A

nuclear model
- the mass of an atom is concentrated at its centre, the nucleus
- the nucleus is positively charged

75
Q

what was niels bohr’s model of the atom?

A

planetary model
- electrons orbit the nucleus in shells.
- The shells are at certain distances from the nucleus.

76
Q

what was chadwick’s model of the atom?

A
  • found evidence for the existence of particles in the nucleus with mass but no charge.
  • These particles are called neutron

CHEM 2.0 (14 decks)

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