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key concepts Flashcards

1
Q

1st model of atom

A

-Dalton
-early 19th
-tiny solid balls
-can’t be broken down
-atoms of an element are identical
-atoms of different elements are different
-during chemical reactions atoms rearrange to make different substances

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2
Q

2nd model of atom

A

-plum pudding
-jj thomson
-positively charged ball with electrons scattered throughout

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3
Q

3rd model of atom

A

-rutherford
-gold foil experiment
-nuclear atom, tiny +ve nucleus at centre of electron cloud, mostly empty space

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4
Q

gold foil experiment

A

-rutherford, geiger + marsden fired +ve alpha particles at gold sheet
-expected: pass thru, some slightly deflected
-deflected more than expected, some backwards

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5
Q

4th model of atom

A

-bohr
-electrons exist in fixed shells with fixed energy

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6
Q

eletron mass + charge

A

-1/1835
–1

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7
Q

proton mass + charge

A

-1
-+1

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8
Q

neutron mass + charge

A

-1
-0

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9
Q

what is atomic number

A

proton number (whole number, usually above element symbol)

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10
Q

what is mass number

A

neutron + protons (usually below element symbol)

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11
Q

isotopes

A

same atomic number, different mass number

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12
Q

how to find relative atomic mass

A

Ar = ((mass x amount usually %) + (mass x amount))/total number of atoms, amount + amount

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13
Q

Mendeleev’s periodic table

A

-ordered by relative atomic mass
-left gaps for undiscovered elements
-switched some to make properties fit better

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14
Q

modern periodic table

A

-groups where the elements have similar
properties
-periods in order of increasing atomic number
-by atomic number

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15
Q

usual electron figuration (n.n.n…)

A

2.8.8…

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16
Q

what does period number show

A

Number of shells

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17
Q

what does group number show

A

Number of electrons in outermost shell

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18
Q

what are the rows +
columns called?

A

-periods
-groups

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19
Q

Which part of the atomic structure has most effect on the chemical properties and reactions of an element?

A

outer electron shell

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20
Q

What changes in atomic structure occur as you move from left to right along the horizontal rows in the periodic table?

A

The number of protons in the nucleus increases by one

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21
Q

what is an ion

A

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

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22
Q

cation charge

A

postive (paw-sitive, cat-ions)

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23
Q

anion charge

A

negative

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24
Q

what ions do metals + non-metals form

A

-cations
-anions

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25
how do ionic bonds form
-between metal + non-metal -trade electrons + become ions -oppositely charged ions are attracted
26
how are ions in ionic compound arranged
regularly with oppositely charged ions next to each other, ionic lattice
27
properties of ionic substances
-high bp + mp -conduct when molten
28
charge of carbonate ion
2-
29
charge of lead
2+
30
What happens when sodium and chlorine atoms form sodium chloride?
When sodium chloride is formed an electron transfers from a sodium atom to a chlorine atom. This happens because sodium's electronic configuration is 2.8.1 and chlorine's electronic configuration is 2.8.7. Transferring one electron from sodium to chlorine makes both outer shells full and therefore stable.
31
covalent bond
formed when a pair of electrons is shared between two atoms, usually non-metals
32
what is a molecule
consists of a group of two or more atoms joined together by covalent bonds
33
size of molecule
typically around 0.1 nm or 10-10 m across
34
Properties of simple molecular substances
-low mp + bp, weak intermolecular forces -can't conduct
35
strength of bonds between: a)atoms b)molecules
a)covalent + strong b)weak intermolecular
36
simple molecules
contain a set number of atoms joined by covalent bonds
37
giant covalent substances
contain many atoms joined by covalent bonds
38
properties of giant covalent substances
-high mp + bp -don't conduct, except graphite -insoluble in water, can't for strong enough attractions with water molecules
39
silica
main compound in sand + example of giant covalent substance
40
diamond structure
-each carbon atom is joined to four other carbon atoms by covalent bonds -carbon atoms form a regular tetrahedral network structure -no free electrons
41
diamond properties + uses
- strong covalent bonds, makes diamond very hard -cutting tools, such as diamond-tipped glass cutters and oil rig drills.
42
graphite structure
-each carbon atom is joined to three other carbon atoms by covalent bonds -carbon atoms form a hexagonal layered network structure -layers have weak forces between them so can slide over each other -each carbon atom has one un-bonded outer electron, which are delocalised
43
garphite properties + uses
-Delocalised electrons are free to move, so graphite can conduct electricity, used for electrodes in batteries + for electrolysis -layers in graphite can slide over each other as forces between them are weak, makes graphite slippery, so it is used as a lubricant
44
Graphene structure + properties
-form of carbon -structure resembles a single layer of graphite -high mp, regular arrangement of carbon atoms joined by covalent bonds -conducts electricity, delocalised electrons
45
Fullerenes + example
-molecular form of the element carbon -nanotubes, buckyballs
46
Nanotubes structure + properties
-resembles a layer of graphene, rolled into a tube shape -high tensile strength -strong -conduct electricity
47
Buckyballs structure + properties
-spheres or squashed spheres of carbon atoms -not classed as giant covalent networks, made up of large molecules -slippery and have lower melting points than graphite/diamond, weak intermolecular forces
48
Polymers
consist of large molecules that contain chains of carbon atoms of no set size
49
Which type of bonding and structure has billions of non-metal atoms held together, in a regular structure, by sharing electrons between atoms?
Giant covalent structures
50
properties of metals
Shiny High melting points Good conductors of electricity Good conductors of heat High density Malleable
51
properties of non-metals
Dull Low melting points Poor conductors of electricity Poor conductors of heat Low density Brittle
52
Metallic structure and bonding
-positive metal ions + a 'sea' of delocalised electrons
53
explain malleability
-Metals are malleable because layers of ions can slide over each other when a force is applied -Metallic bonding allows the metal to change shape without shattering
54
explain conductivity
-When a voltage is applied to a metal, delocalised electrons travel through the lattice structure -The movement of these charged particles forms an electric current
55
4 types of bonds
-ionic -simple -giant -metallic
56
ionic bonds summary
-metals + non -loss/gain of electrons - +ve + -ve ions formed attract eachother -ionic lattice structure
57
simple bonds summary
-non-metals -share pairs of electrons between atoms -Small groups of atoms held together -molecular structure
58
giant bonds summary
-Non-metals -Share pairs of electrons between atoms -Billions of atoms are held together -Giant covalent lattice structure
59
metallic bonds summary
- Metals -Outer electrons free to move -Billions of positive metal ions -Giant metallic lattice structure
60
what is Ar
relative mass of its atoms compared to the mass of a particular carbon atom
61
how to calculate Mr
1.work out how many atoms of each element are in the chemical formula 2.add together the Ar values for all the atoms of each element
62
how to find what percentage of a compound is a particular element
(mass of element in compound/Mr) x 100
63
how to find empirical formula
1 Write the element symbols 2 Write the masses 3 Write the Ar values 4 Divide masses by Ar 5 Divide by the smallest number 6 Write the formula
64
what does Ar mean
relative atomic mass
65
what does Mr mean
relative formula mass
66
conc units
g dm^-3
67
mass units
g
68
volume units
dm^3
69
1dm^3 = __cm^3
1000cm^3
70
what value from the periodic table do you use in Ar and Mr calculations
mass number
71
equation with mass, Mr and mol
mass = Mr x mol
72
what is a mole
relative atomic mass (Ar) of an element in grams, or the relative formula mass (Mr) in grams if it's a compound
73
what is the Avogadro constant
the number of carbon atoms in exactly 12 g of carbon-12, 12C.
74
what is 1 mol defined as
the Avogadro constant number of particles
75
how to calculate the number of particles in a substance
number of particles = 6.02 × 10^23 × mol
76
how to calculate the number of atoms in a substance
1.number of particles = 6.02 × 10^23 × mol 2. x by numbers in formula e.g. H2O would have x 3
77
calculating mass with Mr and moles
-mass in g = Mr(or Ar) x no. moles -m = Mr x mol
78
what is a limitting reactant
reactant that's entirely used up
79
what is an excess reactant
reactant left over
80
how to find how much of a productcan be made using limitting reactant
1.find moles of given reactant (mass/Mr) 2.mass of product = Mr x amount(moles)
81
how to find stoichiometry of a reaction
1.write formulae of substance 2.calculate amounts (mol) 3.divide both by the smaller amount 4.balance as normal

chemistry (4 decks)

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