topic one: Atomic Structure and the Periodic Table Flashcards
what is the charge of a proton, neutron and electron?
proton - positive, +1
neutron- neutral, 0
electron- negative, -1
what is the relative mass of a proton, neutron and electron?
proton- 1
neutron- 1
electron- 1/2000
what is the overall charge of an atom?
neutral, or 0
why do atoms have a neutral charge?
they have the same number of positive protons and negative electrons, so the charges cancel out.
what does the atomic number of an atom tell you?
the number of protons.
what does the mass number of an atom tell you?
the total number of protons and neutrons.
how can you use the atomic number and mass number of a given atom, to work out how many neutrons it has?
number of neutrons = mass number - atomic number.
what is an element?
substance made up of only one type of atom, so where all the atoms of a substance have the same number of protons.
approximately how many different elements are there?
100.
what is an isotope?
different forms of the same element, which have the same number of protons but a different number of neutrons.
what does relative atomic mass mean?
average mass of all the isotopes of an element, taking into account the abundance and mass number of each isotope.
what is the formula for relative atomic mass?
sum of: (isotope abundance x isotope mass number)/ sum of abundances of all isotopes.
what is a compound?
substance formed from two or more elements, where the atoms of each are in fixed proportions, and are held together by chemical bonds.
what is a mixture?
group of different elements or compounds which are not chemically bonded.
what is a molecule?
substance that contains two or more atoms held together by chemical bonds.
what is a reactant?
the starting materials in a chemical reaction.
what is a product?
new substances produced by a chemical reaction.
which are the 6 methods through which mixtures can be separated?
1.filtration
2.chromatography
3.crystallisation
4.evaporation
5.simple distillation
6.fractional distillation
what is filtration used for?
used to separate insoluble solids from liquids.
describe the technique for filtration.
- place a piece of filter paper in a funnel, and put the funnel over a beaker.
- pour your mixture through the funnel.
- any insoluble solids will be caught by the filter paper, we call this the residue.
4, any liquid or dissolved substances will pass straight through, we call this the filtrate.
what is evaporation used for?
to separate a dissolved solid from a liquid.
describe the technique for evaporation.
heat your solution until all of the solvent evaporates, and only solids remain. (normally done by placing the solution in an evaporating dish on a tripod, and heating with a Bunsen burner
describe the technique for crystallisation.
- pour the solution into an evaporating dish.
- heat it with a Bunsen burner.
- stop heating when crystals start to form and allow to cool down.
- either allow the rest of the water to evaporate, or filter out the crystals in an oven.
- dry crystals.
what is the benefit of using crystallisation rather than evaporation as a separating technique?
the excess heat used in evaporation can sometimes cause the crystals to break down by thermal decomposition.
how would you isolate the sand and salt from a mixture of salt and sand?
- place mixture in water and stir. the salt will dissolve but the sand wont.
- pour mixture through filter paper and funnel. The sand will get stuck on the filter paper.
- evaporate water by heating. this will leave behind the salt.
what is chromatography used for?
separates the components of a mixture based on their solubility.
what is a ‘pure’ substance?
a substance that only contains one type of element or compound.
what is a solution?
a mixture that contains a solute (solid) dissolved in a solvent (liquid).
what do soluble and insoluble mean?
soluble - a substance that can dissolve in liquid
insoluble - cannot dissolve in liquid.
what is the purpose of simple distillation?
used to separate a liquid from a mixture, but when we want to keep the liquid.
describe the process of simple distillation.
- place solution in a flask and heated so that the liquid evaporates into vapour.
- the vapour will pass into a condenser where it condenses back into a liquid.
- the liquid is collected into a beaker.
why can you not use simple distillation for mixtures that contain multiple different liquids?
if the different liquids have similar boiling points, those liquids may evaporate at the same time.
when would you need to use fractional distillation rather than simple distillation?
when the mixture contains multiple liquids with similar boiling points.
how does fractional distillation work?
1, solution is placed into a flask and is gently heated.
2. the liquid with the lowest boiling point evaporates into a vapour and passes through the fractionating column.
3. as it passes into the condenser it condenses back into a liquid, and is collected in a beaker.
4. if another liquid has evaporated, it would have condensed again while passing through the Fractionating column.
5. as the temperature is increased, the process repeats for the liquid with the second lowest boiling point, which is collected in a different beaker and so on.
summarise John Dalton’s theory.
described atoms as solid spheres, and said that different-sized spheres made up the different elements.
summarise JJ Thompson’s findings and resulting theory.
he found that atoms contain even small, negatively charged particles - electrons.
He proposed a new theory in which the atom was a ball of positive charge with discrete electrons throughout it . It was known as the plum pudding model.
what was the plum pudding model, and who proposed it?
the plum pudding model was a theory proposed by J J Thompson in which the atom is a ball of positive charge, with discrete electrons throughout it. like a pudding with bits of plum spread throughout it.
what was the experiment carried out by Ernest Rutherford and its results?
him and his students conducted the alpha particle scattering experiments where they fired positively charged alpha particles at an extremely thin sheet of gold.
Results: rather than all of the alpha particles passing straight through the sheet of gold, some were deflected to the side, and a small number were even deflected backwards.
what is the nuclear model of the atom , and who proposed it?
proposed by Ernest Rutherford.
the nuclear model of the atom is the idea that each atom is composed of a small positively charged nucleus at the centre, surrounded by a ‘cloud’ of negative electrons.
what was the main issue with the nuclear model of the atom?
the electrons should be attracted to the positive nucleus, so the atom should just collapse
what did Niels Bohr propose?
electrons orbit the nucleus in shells, which are a fixed distance from the nucleus.
This was in contrast to Ernest Rutherford’s theory in which the electrons were spread in a ‘general cloud’ around the nucleus.
what did James Chadwick discover?
neutral particles called neutrons.
where are the electrons located in an atom?
found in shells (or ‘energy levels’), and orbit the nucleus.
what do we mean by the ‘electronic structure’ ore ‘electronic configuration’ of an atom?
refers to the arrangement within an atom, i.e. how many electrons are in each shell.
how many electrons are found in the first, second and third shells of an atom?
1st shell: 2 electrons, 2nd shell: 8 electrons, 3rd shell: 8 electrons.
if an an atom has 15 electrons in total, how many will it have in each shell?
2 in the first shell, 8 in the 2nd shell, 5 in the 3rd shell.
what is meant by an atoms ‘outer shell’?
the shell of electrons that is furthest from the nucleus.
in the 1800’s, how were elements arranged in the periodic table?
by atomic weight.
how did Mendeleev arrange his periodic table?
- He mainly ordered the elements by increasing atomic weight.
- He arranged elements that had similar properties into rows (periods), and columns (groups).
- He left gaps.
Why did Mendeleev leave gaps in his table?
to ensure that elements with similar properties stayed in the same group, and to leave space for elements that hadn’t been discovered yet.
How are elements arranged in the modern periodic table?
- Increasing atomic number.
- Patterns of chemical and physical properties (periods/groups).
why are elements put into groups?
To group together elements that have similar properties.
What does the group number tell you about the atoms of an element?
the number of electrons in the outer shell.
what does the period tell you about the atoms of an element?
the number of shells.
what name is given to the elements in group 1?
Alkali metals.
what name is given to the elements in group 7?
Halogens.
what name is given to the elements in group 0?
Nobles gases.
are most elements metals or non-metals?
most are metals.
do metals form positive or negative ions when they react?
positive ions.
what are the properties of metal?
- Strong
- Malleable
- Ductile
- Good conductors of electricity and heat
- High melting and boiling points.
- Dense
7.Shiny
where on the periodic table are transition metals found?
between group 2 & 3.
do non-metals form positive or negative ions when they react?
negative ions.
what are the properties of group 1 metals? (alkali)
- Soft
- Low density
- Very reactive
- Weak
- Relatively low melting points (compare to other metals)
what are the properties of non-metals?
- Brittle
- Dull
- Lower melting and boiling points
- Poor conductors of electricity
- Lower density
state the 3 trends seen in group 1 metals as you go down the periodic table.
- Increased reactivity.
- Lower melting and boiling point
3.Higher atomic mass.
what is the reaction between a group 1 element and water?
metal hydroxide + hydrogen.
what is the reaction between a group 1 element and chlorine?
metal chloride
what is the reaction between a group 1 element and oxygen?
metal oxide
why do alkali metals become more reactive down the group?
- As you go down the group, atomic radius and shielding increase.
- This means there is a weaker electrostatic attraction between the outer-most electrons and the nucleus.
- This means that the amount of energy required to lose the outer-most electron decreases, which makes it easier for a reaction to occur.
are halogens metals or non-metals?
non-metals.
name the first 4 group 7 elements, starting at the top of the group.
- Fluorine
- Chlorine
- Bromine
- Iodine
what is the state and colour of fluorine at room temp?
yellow gas.
what is the state and colour of chlorine at room temp?
green gas.
what is the state and colour of bromine at room temp?
red-brown liquid.
what is the state and colour of iodine at room temp?
dark grey solid, which gives off purple fumes.
state the three trends in the group 7 elements as you go down the periodic table.
- Decreased reactivity
- Higher melting/boiling points
- Higher atomic mass
are halogens monoatomic or diatomic?
diatomic (exist in pairs).
why do halogens become less reactive as you move down group 7 of the periodic table?
- As you go down the group, atomic radius and shielding increase
- This means there is a weaker electrostatic attraction between the nucleus ans the electron it is trying to gain
- This means more energy is required for a reaction to occur.
what type of bonds do halogens form with metals?
ionic bonds.
what is a halogen displacement reaction?
a reaction which a more reactive halogen displaces a less reactive one.
could chlorine displace the bromine in potassium bromide?
yes, because chlorine is more reactive than bromine.
are noble gases metals or non-metals?
non-metals.
Noble gases are ‘inert’ , what does inert mean?
not reactive, so they don’t react with other atoms.
why are nobles gases inert?
they already have a full outer-shell of electrons, so don’t need to gain or lose any electrons.
what is the physical state of group 0 elements at room temp?
gaseous.
state and explain the trend in the boiling points of noble gases as you move down group 0 of the periodic table.
boiling points increase as you move the group. This is because the atoms have more electrons, and so can form more Intermolecular forces, which will require more energy to overcome.
are noble gases monoatomic or diatomic/
monoatomic (exist as single atoms).
