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CHEMISTRY > SC1: key concepts in chemistry > Flashcards

SC1: key concepts in chemistry Flashcards

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1
Q

mnemonic for diatomic elements

A

I Bring Clay For Our New House:

iodine, bromine, chlorine, fluorine, oxygen, nitrogen, hydrogen

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2
Q

compound

A

a chemical combination of two or more elements

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3
Q

what does a chemical formula show?

A

how many atoms there are in each element of a compound

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4
Q

what is a covalent bond?

A

a chemical bond formed when two or atoms share electrons

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5
Q

what are covalent bonds between?

A

non-metals

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6
Q

what is an ionic bond?

A

formed when one or more electrons are transferred from one atom to another

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7
Q

what are ionic bonds between?

A

metals and non metals

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8
Q

what is an ion?

A

the charged particle formed when an atom loses or gains electrons

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9
Q

what happens in a chemical reaction?

A

the atoms of ions in reactants separate from one another and join back together in a different way to form products

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10
Q

what is an aqueous solution?

A

a solution in which water is the solvent

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11
Q

what is a precipitation reaction

A

when two soluble substances react together to make a product which is insoluble (the precipitate)

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12
Q

how is a precipitation reaction modelled?

A

with a balanced ionic equation

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13
Q

what are spectator ions?

A

ions that do not participate in a reaction

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14
Q

what is a hazard?

A

something with the potential to cause harm

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15
Q

what is a risk?

A

the chance that a hazard will cause harm

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16
Q

what is a precaution?

A

something that can be done to reduce a risk of harm

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17
Q

what is a risk assessment?

A

something that describes the hazards and risks of harm & what precautions are needed to work safely

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18
Q

what is the order of atomic structure discovery?

A
  1. john dalton
  2. j.j thompson
  3. ernst rutherford
  4. niels bohr
  5. james chadwick
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19
Q

john dalton

A

-atoms can’t be broken
-there is nothing smaller than an atom

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20
Q

j.j thompson

A

-discovered the electron (1904)
-atoms made up of small, negatively charged atoms in a positively charged area
-plum pudding model

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21
Q

ernst rutherford

A

-discovered the nucleus in 1909
-fired alpha particles (positively charged) at a thin gold lead in a vacuum, most passed through, a few were deflected, some came back
-small positively charged nucleus surrounded by empty space, electrons orbited nucleus
-nucleus was heavier than could be explained with only protons so ernst proposed neutrons
-ernst couldn’t explain why electrons didn’t collapse into the nucleus

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22
Q

niels bohr

A

-1913: discovered that electrons move around the nucleus in orbits called electron shells
-worked with rutherford
-rutherford-bohr model was supported by scientists

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23
Q

what happens when atoms absorb energy?

A

their electrons move to higher energy levels

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24
Q

mass of an electron

A

1/1835

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25
Q

what is atomic mass?

A

protons + neutrons + electrons

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26
Q

what is an atomic number?

A

the number of protons/electrons in an atom

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27
Q

what are isotopes?

A

atoms of the same element with different numbers of neutrons

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28
Q

what is RAM?

A

relative atomic mass

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29
Q

RAM facts

A

-not whole numbers
-mean relative mass of atoms of different isotopes in an element

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30
Q

what is the formula for RAM?

A

(% of isotope 1 × mass of isotope 1) + (% of isotope 2 x mass of isotope 2) / 100

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31
Q

mendeleev’s periodic table

A

-arranged by increasing atomic mass
-put similar properties below each other in groups
- left gaps for yet to be discovered elements
-looked at the chemical and physical properties of the elements next to a gap to predict the properties of these undiscovered elements

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32
Q

modern periodic table

A

-arranged by increasing atomic number
-rows = periods
-columns = groups (elements w similar
properties)
-metals on left side, non-metals on right

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33
Q

what is electron configuration?

A

the arrangement of electrons in an atom

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34
Q

how is electron configuration linked to an elements position on the periodic table?

A

-the number of shells is the period the element is in
-the number of electrons in the outermost shell is the group number of the element
-the number of electrons in all shells is the elements atomic number

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35
Q

why do elements in the same group have similar properties?

A

they have the same amount of electrons in their outer shell, when atoms collide & react, the outer shells interact, so because they have the same amount of electrons in their outermost shell, they have similar properties

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36
Q

valency

A

equal to the number of electrons that each atom needs to gain, lose or share to fill its outer shell

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37
Q

what is an ion?

A

an atom that has lost or gained electrons to obtain a full outer shell

38
Q

what is an ionic compound?

A

a compound that consists of positive and negative ions

39
Q

anion

A

negative ion

40
Q

cation

A

positive ion

41
Q

dot and cross diagram

A

a drawing to show only the arrangement of electrons of the atoms or bonding of a simple molecular structure

42
Q

ionic lattice

A

regular repeating arrangement of particles

43
Q

why is an ionic lattice formed?

A

the positive and negative ions attract one another and form a regular pattern with oppositely charged ions next to eachother

44
Q

why do solid ionic compounds form crystals?

A

the lattice arrangement continues in three dimensions

45
Q

what is an ionic lattice held together by?

A

ionic bonds

46
Q

what direction(s) do ionic bonds act in?

A

any direction

47
Q

naming ionic compounds

A

ide = 2 elements
ate = 3 or more with one oxygen

48
Q

why do ionic compounds have high melting and boiling points?

A

because of the strong electrostatic attraction between ions, it takes a lot of energy to overcome this attraction and break the many strong bonds to melt or boil the compounds

49
Q

why do ionic compounds conduct electricity only when molten or aqueous?

A

the ions are free to move and carry charge

50
Q

polyatomic ion

A

an ion made of two or more atoms

51
Q

covalent bonds

A

bonds created by sharing electrons with other atoms

52
Q

molecule

A

a group of atoms bonded together covalently

53
Q

what will molecules of the same element and compound always have?

A

a set size

54
Q

simple molecule

A

molecule made up of a small number of atoms held by covalent bonds

55
Q

why can’t atoms and molecules be seen with light microscopes?

A

they’re too small

56
Q

why do simple molecular substances have low melting and boiling points?

A

there are weak intermolecular forces between the molecules that do not require much energy to overcome

57
Q

why can’t simple molecular substances conduct electricity?

A

they have no charge

58
Q

what are giant covalent bonds?

A

many atoms joined by covalent bonds

59
Q

why do giant covalent bonds have a high melting and boiling points?

A

lots of energy needed to overcome strong bonds

60
Q

why aren’t giant covalent bonds electric conductors?

A

they have no charge

61
Q

why are giant covalent lattices insoluble?

A

the covalent bonds are far too strong to be broken by interaction with solvents (a substance can dissolve with water if it forms enough attractions with water molecules

62
Q

diamond (giant covalent lattice, form of carbon)

A

-each carbon atom joined to four other carbon atoms by covalent bonds
-no free electrons
-tetrahedral structure

63
Q

what are the properties of diamonds?

A

-diamonds are very hard due to the rigid structure of the carbon atoms held together by covalent bonds
-doesn’t conduct electricity
-high melting point

64
Q

what can diamonds be used for?

A

cutting tools

65
Q

graphite (giant covalent lattice, form of carbon)

A

-each carbon atom is joined to three other carbon atoms by covalent bonds
-hexagon layered network structure
-the layers have weak forces between them & can slide over one another
-each carbon atom has one un bonded outer electron which is delocalised

66
Q

properties of graphite

A

-can conduct electricity due to the delocalised electron
-slippery due to the weak forces

67
Q

uses of graphite

A

-lubricants
-pencils
-electrodes in batteries

68
Q

graphene (form of carbon)

A

structure resembles single layer of graphite

69
Q

properties of graphene

A

-high melting point & strong bc of regular arrangement of carbon atoms joined by covalent bonds
-conduct electricity well due to delocalised electrons

70
Q

fullerene (very large molecule)

A

a molecular form of carbon that consists of atoms arranged in the shape of a hollow sphere

71
Q

what are two fullerenes?

A

-nanotubes
-buckyballs

72
Q

nanotubes

A

resembles a layer of graphene, rolled into a tube shape

73
Q

properties of nanotubes

A

-high tensile strength, as in the tension that can be withstood without breaking
-conduct electricity due to delocalised electrons
-strong

74
Q

buckyballs

A

spheres or squashed spheres of carbon atoms

75
Q

properties of buckyballs

A

-slippery as there are weak intermolecular forces between buckyballs
-lower melting points than graphite or diamond

76
Q

metals properties

A

-shiny
-high melting points and densities,
-malleable (can be shaped without breaking)
-high density (high mass for its size)
-ductile (can be drawn into a long wire without snapping or breaking)
-good electric & heat conductors (delocalised atoms can move through the lattice structure & form an electric current)

77
Q

where are metals located on the periodic table?

A

left

78
Q

where are nonmetals located on the periodic table?

A

right side

79
Q

metal structure

A

positive ions in a sea of delocalised electrons

80
Q

non metal properties

A

-dull
-brittle (shatter when hit)
-poor electric & heat conductors
- low melting points

81
Q

relative formula mass

A

the sum of the relative atomic masses of the elements as given in the formula

82
Q

empirical formula

A

the simplest whole number ratio of atoms

83
Q

calculating empirical formula

A
  1. write out element symbols
  2. write out the mass/percentage of each element
  3. write Mr values
  4. divide masses by Mr
  5. divide by smallest number
  6. multiply (if needed) for integers
  7. write formula
84
Q

law of conservation of mass

A

atoms aren’t created or destroyed in a chemical reaction, they join together differently than before the reactions to form products, this means that the total mass stays the same

85
Q

reactions in a closed system

A

no substance enters or leaves, mass stays same

86
Q

reactions an non enclosed system

A

-substances can enter or leave
-if a gas escapes, the total mass will look as if it has decreased
-if a gas is gained, the total mass will look as if it has increased
-the total mass stays the same if the mass of the gas is included.

87
Q

concentration formula

A

mass of solute/volume of solvent

88
Q

concentration

A

how much solute is dissolved in a solvent

89
Q

mass formula (moles)

A

mass = mr x moles

90
Q

when does a reaction finish?

A

when one of the reactants is all used up

91
Q

what is a limiting factor in a reaction?

A

a reactant that is used up first in a chemical reaction

92
Q

what does the mass of the product formed in a reaction depend on?

A

the limiting reactant, this is because no more product can form when the limiting reactant is all used up

CHEMISTRY (9 decks)

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