Chemistry Unit 2 Revision Cards

Who devised the Periodic Table?
Mendeleev
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How did he do it?
He put the elements in order of the relative atomic mass, then checked the properties of the elements and their compounds, he swapped some so that the properties lined up
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Was this complete?
no, not all of the elements had been discovered so he left gaps where these fitted. They have all been discovered and fit with the predictions
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Where are metals on the periodic table?
metals are on the left hand side and in the middle
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what is the structure of an atom?
atoms have protons and neutrons in a central nucleus and has electrons that lie on outer shells of the atom
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how big is the nucleus?
the nucleus is very small compared to the rest of the atom
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what is unique to each element?
the atomic number - number of protons in the nucleus
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what are the relative charges of each part of the atom?
proton - +1 , neutron - 0 , electron - -1
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what are the relative masses of each part of the atom?
proton - 1 neutron - 1 , electron - 1/1840
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how many protons are there compared to electrons in each atom?
the number of protons = the number of electrons
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what is the atomic number?
the number of protons in the nucleus
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what is the mass number?
the total number of protons and neutrons in the nucleus
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relative atomic mass
mass of an electron which is too small for normal units
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what do the periods indicate on the periodic table?
elements are arranged in order of increasing atomic number in rows
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what do the groups indicate on the periodic table?
elements with similar properties are placed in the same vertical column
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what are isotopes?
atoms of the same element with a different number of neutrons
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what could this result in?
the relative atomic mass not being a whole number
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how can you calculate the relative atomic mass?
mass number (of each isotope) x its relative abundance (all added together) / 100
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what are the rules of filling electron shells?
2 in the first shell, up to 8 in the remaining shells
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how do you know the number of occupied shells?
this is the same as the row (period number)
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how do you know the number of electrons in the outer shell?
this is the same as the column (group number)
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what do atoms of different elements form?
they combine to form compounds by the formation of new chemical bonds
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how are ionic bonds formed?
by the transfer of electrons do produce cations and anions
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what is an ion?
an atom or group of atoms with a positive or negative charge
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how do sodium and chloride ions react?
sodium atoms lose electrons and chlorine atoms gain electrons. the sodium and chlorine atoms have opposite charges, and they attract eachother, this creates ionic bonds between the ions and a compound is formed
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what is an ionic compound formed between a metal and non metal called?
a salt
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what does 'ide' mean at the end of a compound?
no extra oxygen is presemt
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what does 'ate' mean at the end of a compound?
oxygen is part of the compound
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what is the method of working out the formula of a compound?
swap the numbers that give the charge for each ion and write them after the relevant symbol
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what structure does an ionic compound have?
a lattice structure consisting of a regular arrangement of ions, held together by very strong electrostatic forces between oppositely charged ions
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what are some properties of ionic substances (sodium chloride and magnesium oxide)
high melting and boiling points, solid at room temp, have to be heated strongly to melt, does not conduct electricity as solid but does when molten
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what are the rules for something being insoluble?
most carbonates, most hydroxides (except for common salts of sodium, potassium, ammonium)
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what are the rules for something being soluble?
all nitrates, most chlorides (except silver and lead chloride), most sulfates (except barium, lead and calcium sulfate)
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how can insoluble salts be formed?
insoluble salts can be formed as precipitates by the reaction of suitable reagents in solution
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what method is needed to prepare a pure dry sample of an insoluble salt?
precipitation
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how does precipitation work?
mix solutions, filter the mixture, the insoluble salt is trapped in the filter paper, wash the salt with pure water, leave the salt to dry on filter paper
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what is barium sulfate used for?
it is given as a 'barium meal' to x-ray patients
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why is it used for this?
because it is opaque to x-rays, so it shows up well on the picture, it is safe to use as barium is toxic but barium sulfate is insoluble
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what is the test for sodium ions? (Na +)
flame test - turns yellow
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what is the test for potassium ions? (K+)
flame test - turns purple
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what is the test for calcium ions? (Ca2+)
flame test - turns red
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what is the test for copper ions? (Cu2+)
flame test - turns green/blue
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what is the test for carbonate ions? (CO32-)
dilute acid - identify carbon dioxide evolved
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what is the test for sulfate ions? (SO42-)
dilute hydrochloric acid + barium chloride solution - seeing if white precipitate forms
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what is the test for chloride ions? (Cl-)
dilute nitric acid +silver nitrate solution
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what is spectroscopy?
a type of flame test used to detect the presence of very small amounts of elements
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what elements were discovered this way?
rubidium and caesium were discovered when scientists spotted colours in parts of the spectrum they had not seen before
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what is a covalent bond?
a pair of electrons shared between two atoms
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what does covalent bonding result in?
the formation of molecules
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what are the properties of simple molecular covalent compounds?
weak forces between molecules, low melting and boiling point, does not conduct electricity
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what are the properties of giant molecular covalent compounds?
bonds are strong, melting points and boiling points are high
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what are the properties of diamond?
strong, does not conduct electricity
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what is the use of diamond?
used for cutting tools
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what are the properties of graphite?
weak forces between layers, does not conduct electricity, soft, layers slide over each other easily
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what are the uses of graphite?
used as lubricant and can be used to make electrodes
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how can you separate two immiscible liquids?
use a separating funnel
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what is the method of using a separating funnel?
place mixture in funnel, beaker underneath, open tap until most of lower liquid has ran out, put a clean beaker underneath and run last bit/overlap out, use final beaker for second liquid
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how can you separate two miscible liquids?
by fractional distillation
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what is the method of fractional distillatiom?
mixture is heated, and the vapours pass into a fractionating column, as the gases cool down, the ones with the highest boiling points condense first, different liquids are collected at different points in the column
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what can be obtained by the air?
nitrogen and oxygen
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how can air be distilled?
the air is cooled, -185°C is above the boiling point of nitrogen (so it evaporates) but below the boiling point of oxygen (so it stays as a liquid), the top of the column is --190°C, the nitrogen is still a gas but any oxygen is likely to condense
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what is paper chromatography?
a technique used to separate the different substances in inks, paints, dyes, food colourings
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whatis the process of paper chromatograpjy?
drops of dofferent substances put onto paper and allowed to dry, the bottom is dipped into a solvent
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what happens to the samples?
the different compounds in a sample dissolve to different extents in the solvent, ,ore soluble compounds are carried up the paper faster than less soluble ones, so the compounds spread out
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where can chromatography be used?
in the food industry ( check food colourings in food), forensic science (to analyse DNA samples or paints/inks from crime scenes), by museums (to analyse paints and help them to restore old paintings or detect forgeries)
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how can you find out the Rf value?
distance moved from compound/ distance moved by solvent
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what can Rf values be used for?
Rf values can be used to identify compounds from a chromatogram
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is the Rf value of a compound always the same?
the Rf value of a compound is always the same as long as the chromatography is carried out in the same way, under the same conditions
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what group are alkali metals?
group 1
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what group are halogens?
group 7
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what group are noble gases
group 0
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what is the rest of the periodic table known as?
transition metals
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what is the structure of metals?
a regular arrangement of positive ions surrounded by a sea of delocalised electrons
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what are the properties of metals?
malleable and conduct electricity
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what are most metals known as?
transition metala
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what are the properties of transition metals?
high melting points and form coloured compounds
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what can elements and compounds be classified as?
ionic substances, simple molecular covalent substances, giant molecular covalent substances, metals
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what are the properties of ionic substances?
gain/lose electrons to form ions, strong bonds, conduct when molten, not when solid, high melting/boiling points, solids at room temp, many dissolve in water
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Other cards in this set

Card 2

Front

How did he do it?

Back

He put the elements in order of the relative atomic mass, then checked the properties of the elements and their compounds, he swapped some so that the properties lined up

Card 3

Front

Was this complete?

Back

Preview of the front of card 3

Card 4

Front

Where are metals on the periodic table?

Back

Preview of the front of card 4

Card 5

Front

what is the structure of an atom?

Back

Preview of the front of card 5
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