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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
what is atomic mass?
protons + neutrons + electrons
26
what is an atomic number?
the number of protons/electrons in an atom
27
what are isotopes?
atoms of the same element with different numbers of neutrons
28
what is RAM?
relative atomic mass
29
RAM facts
-not whole numbers -mean relative mass of atoms of different isotopes in an element
30
what is the formula for RAM?
(% of isotope 1 × mass of isotope 1) + (% of isotope 2 x mass of isotope 2) / 100
31
mendeleev's periodic table
-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
32
modern periodic table
-arranged by increasing atomic number -rows = periods -columns = groups (elements w similar properties) -metals on left side, non-metals on right
33
what is electron configuration?
the arrangement of electrons in an atom
34
how is electron configuration linked to an elements position on the periodic table?
-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
35
why do elements in the same group have similar properties?
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
36
valency
equal to the number of electrons that each atom needs to gain, lose or share to fill its outer shell
37
what is an ion?
an atom that has lost or gained electrons to obtain a full outer shell
38
what is an ionic compound?
a compound that consists of positive and negative ions
39
anion
negative ion
40
cation
positive ion
41
dot and cross diagram
a drawing to show only the arrangement of electrons of the atoms or bonding of a simple molecular structure
42
ionic lattice
regular repeating arrangement of particles
43
why is an ionic lattice formed?
the positive and negative ions attract one another and form a regular pattern with oppositely charged ions next to eachother
44
why do solid ionic compounds form crystals?
the lattice arrangement continues in three dimensions
45
what is an ionic lattice held together by?
ionic bonds
46
what direction(s) do ionic bonds act in?
any direction
47
naming ionic compounds
ide = 2 elements ate = 3 or more with one oxygen
48
why do ionic compounds have high melting and boiling points?
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
why do ionic compounds conduct electricity only when molten or aqueous?
the ions are free to move and carry charge
50
polyatomic ion
an ion made of two or more atoms
51
covalent bonds
bonds created by sharing electrons with other atoms
52
molecule
a group of atoms bonded together covalently
53
what will molecules of the same element and compound always have?
a set size
54
simple molecule
molecule made up of a small number of atoms held by covalent bonds
55
why can't atoms and molecules be seen with light microscopes?
they're too small
56
why do simple molecular substances have low melting and boiling points?
there are weak intermolecular forces between the molecules that do not require much energy to overcome
57
why can't simple molecular substances conduct electricity?
they have no charge
58
what are giant covalent bonds?
many atoms joined by covalent bonds
59
why do giant covalent bonds have a high melting and boiling points?
lots of energy needed to overcome strong bonds
60
why aren't giant covalent bonds electric conductors?
they have no charge
61
why are giant covalent lattices insoluble?
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
diamond (giant covalent lattice, form of carbon)
-each carbon atom joined to four other carbon atoms by covalent bonds -no free electrons -tetrahedral structure
63
what are the properties of diamonds?
-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
what can diamonds be used for?
cutting tools
65
graphite (giant covalent lattice, form of carbon)
-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
properties of graphite
-can conduct electricity due to the delocalised electron -slippery due to the weak forces
67
uses of graphite
-lubricants -pencils -electrodes in batteries
68
graphene (form of carbon)
structure resembles single layer of graphite
69
properties of graphene
-high melting point & strong bc of regular arrangement of carbon atoms joined by covalent bonds -conduct electricity well due to delocalised electrons
70
fullerene (very large molecule)
a molecular form of carbon that consists of atoms arranged in the shape of a hollow sphere
71
what are two fullerenes?
-nanotubes -buckyballs
72
nanotubes
resembles a layer of graphene, rolled into a tube shape
73
properties of nanotubes
-high tensile strength, as in the tension that can be withstood without breaking -conduct electricity due to delocalised electrons -strong
74
buckyballs
spheres or squashed spheres of carbon atoms
75
properties of buckyballs
-slippery as there are weak intermolecular forces between buckyballs -lower melting points than graphite or diamond
76
metals properties
-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
where are metals located on the periodic table?
left
78
where are nonmetals located on the periodic table?
right side
79
metal structure
positive ions in a sea of delocalised electrons
80
non metal properties
-dull -brittle (shatter when hit) -poor electric & heat conductors - low melting points
81
relative formula mass
the sum of the relative atomic masses of the elements as given in the formula
82
empirical formula
the simplest whole number ratio of atoms
83
calculating empirical formula
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
law of conservation of mass
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
reactions in a closed system
no substance enters or leaves, mass stays same
86
reactions an non enclosed system
-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
concentration formula
mass of solute/volume of solvent
88
concentration
how much solute is dissolved in a solvent
89
mass formula (moles)
mass = mr x moles
90
when does a reaction finish?
when one of the reactants is all used up
91
what is a limiting factor in a reaction?
a reactant that is used up first in a chemical reaction
92
what does the mass of the product formed in a reaction depend on?
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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