Topic 1- Atomic Structures and the Periodic Table. Flashcards
1
Q
what are all substances made of?
A
atoms.
2
Q
what does atoms contain?
A
- protons.
- neutrons.
- electrons.
3
Q
what is the radius of an atom?
A
about 0.1 nanometres ( 1x10-10m)
4
Q
what is the atomic structure of the nucleus?
A
- in the middle of the atom.
- contains protons and nuetrons.
- nucleus has the radius of around 1x10-14m .
- positive charge (protons).
- almost the whole mass of the atom is the nucleus.
5
Q
what is the atomic structure of the electrons?
A
- move around the nucleus in electron shells.
- negatively charged.
- almost no mass.
6
Q
protons?
A
they are heavy compared to electrons and positively charged.
7
Q
neutrons?
A
they are heavy compared to electrons and are neutral.
8
Q
electrons?
A
they are tiny and negatively charged.
9
Q
what describe an atom?
A
the atomic number and mass number.
10
Q
what does the nuclear symbol of an atom tell you?
A
its atomic (proton) number and mass number.
11
Q
what is the atomic number?
A
number of protons.
12
Q
what is the mass number?
A
number of protons + number of neutrons.
13
Q
what’s the number of neutrons?
A
mass number - atomic number.
14
Q
atoms have no what?
A
they have no charge- they are neutral because they have the same number of protons as electrons.
15
Q
so in an atom….
A
number of electrons = atomic number.
16
Q
what is the charge on electrons?
A
it is the same size as the charge on protons but opposite so they cancel out.
17
Q
whats is an ion?
A
an ion is an atom or group of atoms that has lost of gained electrons.
18
Q
what is the proton/electron like in an ion?
A
they don’t have equal amount so they don’t cancel out. this means it has an overall charge.
19
Q
how to calculate number of electrons in a positive ion?
A
atomic number - charge.
20
Q
how to calculate number of electrons in a negative ion?
A
atomic number + charge.
21
Q
what is an element?
A
is a substance made up of atoms that all have the same number of protons in their nucleus.
22
Q
what is the smallest amount of an element?
A
is a single atom of that element.
23
Q
what does the number of protons in the nucleus decide?
A
it decides what type of atom it is.
24
Q
give examples of how the number of proton decides what type it is?
A
- an atom with 1 proton in its nucleus is hydrogen.
- an atom with 2 proton is helium.
25
what are isotapes?
they are atoms with the same number of protons but a different number of neutrons. they have the same atomic number but different mass numbers.
26
how do you describe if an element has a number of isotopes?
you can describe it using relative atomic mass (A,) instead of mass number - average mass.
27
how is A worked out from?
relative atomic mass (A,)= sum of (isotope abundance(amount) x isotope mass number) divided by sum of abundances of all the isotopes.
28
what is a compound?
substances that contain atoms of different elements.
29
what happens during a chemical reaction?
at least one new substance is made. can measure a change in energy- temperature change.
30
how does a compound form?
two or more elements react. the atoms of each element are in fixed proportions in the compound. the atoms are held together by chemical bond. the only way to separate a compound into its elements is by using a chemical reaction.
31
formulas of a compound?
the number of different element symbols tells you how many elements are in the compound.
32
give an example of a formula of a compound?
carbon dioxide, CO2, is a compound made from a reaction between carbon and oxygen. it contains 1 carbon atom and 2 oxygen atoms. as an element, oxygen goes around in pairs of atoms (O2).
33
what if there are brackets in the formula?
it means its times that number everything inside the bracket. Ca(OH)2 = 1 calcium, 2 oxygen and 2 hydrogen.
34
example of chemical reaction shown in a word equation?
methane reacts with oxygen to make carbon dioxide and water:
methane + oxygen ---> carbon dioxide + water.
the chemicals on the left side are called the reactants (react with each other). the chemicals on the right side are called products (been produced from the reactant).
35
do symbol equation need to be balanced or not?
yes they need to be balanced. it should be the same number on both sides.
36
how do you balance it?
putting the numbers in front of the formulas.
37
give an example on how to balance formulas?
```
reaction of sulfuric acid with sodium hydroxide.
H2SO4 + NaOH ---> Na2SO4 + H2O.
left side- H=3, S=1, O=5, Na=1
right side- H=2, S=1, O=5, Na=2
these do not match up so.....
H2SO4 + 2NaOH ----> Na2SO + 2H2O.
```
38
what is easier to separate: compound or mixtures?
mixtures.
39
what does a mixture contain?
at least two different elements or compounds. there aren't any chemical bonds between the two different parts of a mixture?
40
what is air?
it is a mixture of gases, mainly nitrogen, oxygen, carbon dioxide and argon. the gases can be separated out fairly easily.
41
what is crude oil?
it is a mixture of different length hydrocarbon molecules.
42
what methods are used to separate different parts of a mixture?
-filtration.
-crystallisation.
-simple distillation.
-fractional distillation.
-chromatography.
they are all physical methods this means they don't involve any chemical reactions, and don't form any new substances.
43
what does properties describe?
it describes what a substance is like and how it behaves, such as hardness or boiling point.
44
what are the properties of a mixture?
it is just a mixture of the properties of the separate parts. the chemical properties of a substance aren't changed by it being part of a mixture.
45
what is chromatography?
it is a method of separating substances in a mixture. used to separate different dyes in an ink.
46
what is filtration?
separates an insoluble solid from a liquid reaction mixtures.
47
two ways to separate insoluble solids from solutions?
- evaporation- really quick, only can be used it if the salt doesn't break down when it's heated.
- crystallisation- the heat forms crystals.
48
what can be used to separate rock salt?
- filtration.
- crystallisation.
rock salt= a mixture of salt and sand. salt dissolves in water, sand doesn't.
49
what are the two types of distillation?
- simple- separate a liquid from a solution.
| - fractional- separate a mixture of liquids.
50
what did scientists used to think atoms were?
solid spheres- then they found atoms contain even smaller, negatively charged particles (electrons) this led to a model called the 'plum pudding model' being created. this showed the atom as a ball of positive charge with electrons scattered in the ball.
51
what did the experiments prove about the plum pudding model?
it proved the model was wrong. the scientists later carried out alpha particle scattering experiments- they fired positively charged alpha particles at a very thin sheet of gold. the plum model, they expected the particles to go straight through the sheet. instead some particles changed direction more than predicted. small amount went backwards as well. this means plum pudding model couldn't be right.
52
as a result of the plum pudding being proved wrong, what did the scientists come up with?
they came up with the nuclear model of the atom.
- a tiny, positively charged nucleus at the centre of atom.
- most the mass is nucleus.
- the nucleus surrounded by a 'cloud' of negative electrons.
- most of the atom is just empty space.
53
what does Bohr explain?
he changed the nuclear model of the atom. he suggested that the electrons orbit the nucleus in the shells. each shell is a fixed distance from the nucleus. this theory is supported by many experiments- they later showed that his theory was correct.
54
what did the later experiments find?
they found protons and neutrons. more showed that the nucleus can be divided into smaller particles - they each have the same positive charge. they were named protons. experiments by James Chadwick showed that the nucleus contained neutral particles- called neutrons. happened 20 years ago after they all agreed that atoms have nuceli. this led to to a model of the atom- pretty close.
55
what are the electron shell rules?
-sometimes the shells are called energy levels.
-the inner shells are always filled up first- closest to the nucleus.
-only a certain number allowed in each shell:
1st- 2 2nd- 8 3rd-8
-atoms are more stable when they have full electron shells.
-in most atoms, the outer shell is not full- these atoms will react to fill it.
56
how was elements arranged by in the early 1800's?
it was arranged by the atomic mass. scientists has no idea about atomic number so they used relative atomic mass to arrange in a periodic table. they were not complete, because not all elements were found. having them arranged by the atomic mass means some of them were in the wrong group.
57
who was Dmitri Mendeleev?
a scientist from 1869, took all of the known elements and arranged them in a table.
58
what did Mendeleev do?
- he ordered them mainly by their atomic mass.
- sometimes switched position or left gaps in the table- to make sure similar properties of the elements were grouped together.
- some of the gaps haven't yet been found- he predicted the properties.
- new elements were found which fit the gaps- shows his idea's was right.
59
when was isotopes discovered?
it was a while after Mendeleev made his Table of Elements. they have different atomic masses but share the same properties- same position on the periodic table. so Mendeleev was right to swap some elements to keep the properties together.
60
what does the modern periodic table help you see?
it helps you to see patterns in properties.
- there are about 100 elements.
- the elements are laid out in order of increasing atomic number.
- metals on the left and non-metals on the right.
- elements with similar properties are arranged to form columns- called groups.
- the group number is the same as the number of outer shell electrons- except for group 0- helium had 2 electrons in its outer shell and the rest have 8.
- all elements in a group have the same number of electrons in their outer shell- the elements in that group react in similar ways.
- if you know properties of 1 element, you can predict properties of the other elements in the group.
- can make predictions in reactivity.
- the row are called periods- each one represents an other shell of electrons.
61
what are most of the elements?
they are metals.
62
what are metals?
elements which can form positive ions when they react.
63
where are the metals found on the periodic table?
towards the bottom and to the left of the periodic table.
64
where are the non-metals found on the periodic table?
they are at the far right and top of the periodic. they don't usually form positive ions when they react.
65
what does the electronic structure of atoms affect?
it will affect how they will react. the atoms are more stable with a full outer shell so they react by losing, gaining or sharing electrons.
66
where are metal elements?
to the left and towards the bottom- lose electrons quite easily. they form positive ions with a full outer shell.
67
where are non-metal elements?
to the right and near the top- easier for them to share or gain electrons to get a full outer shell.
68
what do all metals have that is in common?
all metals have similar physical properties.
- strong (hard to break), but can be bent or hammered into different shapes (malleable).
- great at conducting heat and electricity.
- have high boiling and melting points.
69
what similarities are there in non-metals?
non-metals don't tend to have the same properties as metals.
- tend to be dull looking.
- more brittle - they will break easily if you try and bend it.
- not always solids at room temperature.
- don't usually conduct electricity.
- often have a lower density.
70
what are group 1 elements known as?
known as the alkali metals.
71
what are group 1 elements?
```
they are reactive, soft metals.
-lithium.
-sodium.
-potassium.
-rubidium.
-caesium.
-francium.
they have one electron in their outer shell- makes them very reactive, also gives them similar properties.
the alkali metals are all soft- low density (quite light).
```
72
what happens when u go down group 1?
the properties of the alkali metals change. for example:
- reactivity increases- the outer electron is more easily lost as it gets further from the nucleus- less attracted to the nucleus.
- melting and boiling points gets lower.
- relative atomic mass goes up.
73
what are the patterns in the properties called?
trends.
74
what do alkali metals form with non-metals?
iconic compounds.
75
what can group 1 easily lose?
can easily lose their 1 outer electron to form a full outer shell so they for 1+ ions easily.
76
what happens when alkali metals reacts with water?
-reaction is vigorous (strong and healthy).
-produce a metal hydroxide and hydrogen gas.
alkali metal + water ---> metal hydroxide + hydrogen.
-metal hydroxide are salts- dissolve in water.
-the more reactive (lower in the group) an alkali metal is the more violent the reaction.
-lithium, sodium and potassium float and more around the surface, fizzing furiously.
-the reaction with potassium gives out enough energy to ignite (set on fire) the hydrogen.
77
what happens when the alkali metal reacts with chlorine?
- they react vigorously when heated in chlorine gas to form white salts called metal chlorides.
- the lower down in the group the reaction becomes more vigorous.
78
what happens when the alkali metal reacts with oxygen?
- react with oxygen to form a metal oxide.
- different types of oxide will form depending on the group 1 metal.
- the metals are shiny but when they react with oxygen in the air they turn dull grey (they tarnish)- because a layer of metal oxide is formed on the surface.
79
what are group 7 elements called?
halogens.
80
what elements are in group 7?
- fluorine.
- chlorine.
- bromine.
- iodine.
- astatine.
81
what do they form as elements?
the halogens form molecules that contains two atoms.
82
what happens as you go down group 7?
the halogens:
- become less reactive - harder to gain extra electron.
- have higher melting and boiling points.
- have higher relative atomic masses.
83
why do all of group 7 elements react in similar ways?
they all have seven electrons in their outer shell.
84
what can halogens form?
they can form molecular compounds.
85
what happens when halogens react with other non-metals?
they share electrons and form covalent bonds- so they can get a full outer shell. these reactions form compounds with simple molecular structures.
86
what do halogens form with metals?
iconic bonds.
- the halogens form 1- ions = halides. for example- fluoride F- , bromide Br- , chloride Cl- , iodide I-
- halides form when halogens bond with metals.
- the compounds ~(halides salt) that form have ionic structures.
87
what are displacement reactions?
reactions that take place between a halogen and the halide salt of a less reactive halogen.
88
what happens while the displacement reaction?
the less reactive halogen changes from a halide (1- ion) to a halogen . the more reactive halogen changes from a halogen into a halide ion and becomes part of the salt.
89
whats an example of displacement reaction?
chlorine is more reactive than bromine, so add chlorine to a solution containing bromine salt, the bromine will be displaced.
90
what are group 0 elements known as?
noble gas.
91
what are group 0 elements?
- helium.
- neon.
- argon.
- krupton.
- xenon.
- radon.
- they are colourless gases at room temperature.
- all have 8 outer shell electrons apart from helium which has two = they have a stable full outer shell.
- the stability makes them unreactive- they don't form molecules easily so elements are single atoms.
- some reactions are carried out in an atmosphere that only contain noble gas.
- is done if the reactants could react with the things in the air instead of taking part in the reaction you are trying to do. it's also done if the products react with things in the air.
92
what are the pattern in the properties of the noble gases?
- as you go down the group, the relative atomic masses of the elements increases = the elements have more electrons.
- more electrons means stronger forces between atoms.
- the stronger the forces , the higher the boiling point- so going down the group means the boiling points increase.
- can predict the boiling point of the other by one boiling point of a noble gas.
