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chemistry > key concepts > Flashcards

key concepts Flashcards

1
Q

bohr model

A
  • electrons were in a shell
  • electrons exist in foxed orbits
  • each shell has a fixed energy
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2
Q

oxidising

A

provides oxygen allowing other materials to burn more fiercely

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3
Q

environmental hazards

A

harmful to organisms and environment

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4
Q

harmful

A

can cause irritation reddening or blistering of the skin

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5
Q

toxic

A

can cause death

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6
Q

corrosive

A

destroys materials including living tissues

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7
Q

highly flammable

A

catches fire easily

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8
Q

Rutherford model

A

gold foil experiment

  • particles went through however some were reflected
  • positively charged nucleus in the centre surrounded by some negatively charged particles and a lot of empty space
  • most particles went through (empty space)
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9
Q

JJ Thomson model

A

solid positively charged sphere ‘pudding’ with negatively charged particles scattered around

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10
Q

what does an atom contain

A

protons, neutrons, electron

equal number of protons and electrons

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11
Q

protons

A

heavy positively charged

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12
Q

neutrons

A

heavy

neutral

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13
Q

electrons

A

hardly any mass
negatively charged
move around the nuelus in electron sheels
tiny but sheels cover a lot of space
size of shells determed by size of aatoms

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14
Q

nucleus

A 
middle of the atom
contains protons and neutrons 
psotive charge 
almost whole mass is concentrated in the muckeus 
tiny
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15
Q

mass number

A

total number of protons and neutrons

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16
Q

atomic number

A

how many protons

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17
Q

isotopes

A

same numbers of protons, different number of neutrons

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18
Q

relative atomic mass

A

the bigger number in the periodic table

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19
Q

who made the first periodic table, what was wrong with it?

A

mendeleev

- some elements ended up in the wrong column due to isotopes

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20
Q

3 ideas in Dalton’s theory on an atom

A
  • atoms can not be created, divided or destroyed
  • atoms join with other atoms to make new substances
  • atoms of the same element are the same
  • atoms of different elements are different
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21
Q

structure of an atom

A

small central nucleus made up of protons and neutrons

electrons orbit the nucleus in shells

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22
Q

radius of the nucleus

A

1 x 10-14
1/10000 of the atomic radius
- densely concentrated

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23
Q

relative atomic mass of protons, neutrons and electrons

A

proton - 1
neutron - 1
electron - 1/2000

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24
Q

relative charges of protons, neutrons and electrons

A

proton - +1
neutron - 0
electron - -1

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25
Q

atoms of the same elements have the same number of …. in the nucleus and this is unique to that element

A

protons

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26
Q

how did mendeelev arrange elements

A

elements arranged with increasing atomic masses

similar properties in groups

left gaps for undiscovered elements

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27
Q

how are elements arranged in modern periodic table

A

in order of increasing atomic number
- similar chemical properties in groups (columns)
- the group number is the number of electrons it has in it’s outer shell
(group 7 has 7 outer shells)

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28
Q

elements in the same group (column) have similar ………….

A

chemical properties

- same number of OUTER SHELL electrons, determines how the atom reacts

29
Q

elements in the same period (row)

A

same number of electron shells

30
Q

max number of electrons allowed in each of the first 3 shells

A

1st - 2
2nd - 8
3rd - 8

31
Q

when are atoms most stable

A

when they have full electron shells

32
Q

what is an ionic bond

A

a bond between a metal and non-metal involving the transfer of electron

33
Q

in terms on electrons what happens to the metal and non-metal when an ionic bond forms

A

the metal atom loses electrons to become a positively charged ion (cation)

the non metal atom gains electrons to become a negatively charged ion (anion)

34
Q

what is an ion

A

an ion is an atom or group of atoms with a positive or negative charge

35
Q

positively charged ion = loss or gain electrons

A

lost

36
Q

negatively charged ion = loss or gain electrons

A

gain

37
Q

why do elements in groups 1,2,6 and 7 readily form ions?

A

so they become more stable and achieve the electron structure of the noble gases (group 8)

38
Q

cations

A

positively charged ions

39
Q

anions

A

negatively charged ions

40
Q

ions formed in group 1 and 2

A

1 - form +1 ions

2 - form +2 ions

41
Q

ions formed in group 6 and 7

A

6 - 2- ions

7 - 1- ions

42
Q

ionic compound that ends in -ide

A

compound contains 2 elements

43
Q

ionic compound that ends in -ate

A

compound contains at least three elements, one of which is oxygen

44
Q

structure of an ionic compound

A
  • lattice structure
  • regular arrangement of ions
  • ions held together by strong electrostatic forces between ions and opposite charges
45
Q

what is a covalent bond

A

a bond formed when an electron pair is shared between two atoms

a molecule forms as a result of covalent bonding

covalent bonds are strong

46
Q

ionic compounds have high OR low melting points?

A

HIGH

strong electrostatic attraction between the positive and negative ions requires a lot of energy to overcome

47
Q

simple molecular compounds have high OR LOW melting points

A

LOW

weak intermolecular forces = little energy to overcome

48
Q

Giant covalent structures high OR low melting points

A

HIGH

lots of strong covalent bonds which require a lot of energy to break

49
Q

how do metals conduct electricity and heat

A

the positive ions are fixed in a sea of delocalised electrons. These electrons are free to move and carry charge/ energy

50
Q

giant covalent structures formed from carbon atoms and their structure and properties

A

graphite

  • each carbon atom bonded to 3 other carbon atoms
  • layers of hexagonal rings of carbon atoms
  • weak intermolecular forces between layers
  • one delocalised electrons per carbon atom
  • soft, slippery
  • conducts electricity
  • uses: electrodes, lubricant

diamond

  • all carbon atom are covalently bonded to four other carbon atoms
  • no delocalised electrons
  • very hard
  • very high melting points
  • doesn’t conduct electricity
  • uses: cutting tools
51
Q

what is a fullerene?

A

a molecule made of carbon, shaped like a closed tube or hollow ball

e.g graphene, C60 (buckminsterfullerene)

weak intermolecular forces

52
Q

properties of buckminsterfullerene (C60)

A
  • slippery
  • low melting point
  • spherical
  • large surface area
  • strong covalent bonds
53
Q

properties of graphene?

A
  • high melting point

- conducts electricity as it has delocalised electrons

54
Q

what is a polymer

A

long chain molecules formed from many monomers

55
Q

properties of metal

A
  • high melting point
  • high density
  • good conductors of electricity
  • malleable and ductile
  • generally shiny
56
Q

why are metals malleable and can conduct electricity

A

the atoms are arranged in uniform rows which can slide over one another

the electrons in the metal are charges that can move

57
Q

properties of non-metals

A
  • low boiling points
  • poor conductors of electricity
  • brittle when solid
58
Q

limitations of dot and cross, 2d and 3d models, ball and stick

A

dot and cross - no lattice structure or ionic bonds, doesn’t shoe relative sizes of atoms or intermolecular forces
2D - only shows one layer, doesn’t show formation of ions
3D - shows spaces between the ions, doesn’t show charges
ball and stick - bonds as sticks instead of forces, doesn’t show how covalent bonds form

59
Q

calculate relative former mass of a compound

A

add together all the relative atomic masses of the atoms in the compound

60
Q

cathode

A

negatively charged electrode - attracts to cation

61
Q

anode

A

positively charged electrode - attracts to anion

62
Q

what are simple molecular substances

A

made up of molecules containing a few atoms joined by covalent bonds.

  • very strong covalent bonds
  • forces of attraction is weak
  • mp and bp are low
63
Q

examples of simple molecular substances

A

hydrogen - 1 electron, simple molecular bond with another hydrogen to achieve full outer shell

water - two H atoms to from 2 single covalent bonds

oxygen - needs two more electrons to complete it’s outer shell

hydrogen chloride - needs 1 more electrode

methane
- can form four covalent bonds with hydrogen atoms to fill up its outer shells

carbon dioxide - shares 2 pairs of electrons with two oxygen atoms to form two double covalent bonds

64
Q

bonding models

A

ionic
giant covalent
metallic
simple molecular (covalent)

65
Q

ionic bonding model

A

found: in most compounds containing metal and non-metal atoms
bonding: ionic bonds formed by the loss and gain of electrons to produce oppositely charged ions that attract on another
structure: billions of ions held together in a lattice structure
properties: high melting point, many are soluble in water, conduct electricity when liquid or in solution (not in solid)

66
Q

simple molecular bonding models

A

found: in most non-metal elements and compounds

bonding; covalent bonds formed when atoms share pairs of electrons

structure: small, distinct groups of atoms
properties: low melting points, few are soluble in water

67
Q

giant covalent boning models

A

found: in a few non-metal elements and compounds
bonding: covalent bonds formed when atoms share pairs of electrons
structure: billions of atoms held together in a lattice structure
properties: high melting point, insoluble in water, most do not conduct electricity (except carbon in graphite)

68
Q

metallic bonding model

A

found: in all metals
bonding: metallic bonds are the electrostatic attraction between positive metal ions and negative delocalised electrons.
structure: billions of ions held together in a giant lattice structure of positive ions in a ‘sea’ of delocalised electrons
properties: high melting point, insoluble in water, , conduct electricity when solid or liquid

chemistry (4 decks)

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