1 Atomic structure and the periodic table 4 Inorganic chemistry and the periodic table

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  • Created by: Dane
  • Created on: 26-01-20 14:03
Which Philosopher suggested all substances are made of atoms
Democritus
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What were the main points in John Dalton's theory
- All elements are made up of indivisible particles called atoms - All the atoms of a given element are identicle and have the same mass - The atoms of different elements have different masses - atoms can be combined to form molecules in compounds
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Who discovered electrons
JJ Thomson
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What was Thomson's idea known as
Plum Pudding Model
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Who discovered radioactivity
Henri Becquerel
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What did Ernest Rutherford discover
There was two types of radioactive substances given out by radioactive material: Alpha rays and Beta rays
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What did Rutherford's colleages Hans Geiger and Ernest Marsden discover in their experiment
- Most alpha particles went straight through the foil - Some of the alpha particles were scattered by the foil - Few alpha particles rebounded from the foil
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What did Rutherford come up with to explain the results of the Geiger-Marsden Experiment
The Nuclear model for the structure of atoms
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Which model did this replace
Thompsons plum pudding model
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What did the work of Thompson, Rutherford and their colleage show... Firstly
atoms have a small positive nucleus surrounded by a much larger region of empty space in which there are are tiny negative electrons
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Secondly...
the positive charge of the nucleus is due to the positive particles which rutherford called protons
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Thirdly...
Protons are about 2000 times heavier than electrons
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Fourthly...
The positive charge on one proton is equal in size but opposite in sign to the negative charge of one electron
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Fifthly...
atoms have equal number of protons and electrons, so the positive charge of a proton cancels out the negative charge of an electron
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Sixthly...
The samllest atoms are those of hydrogen with one proton and one electron, the second smallest being helium with two protons and electrons, and then lithium with three protons and electrons
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What did James Chadwick discover
The extra mass in atoms that explained why the relative masses of hydrogen and helium was not one and two respectively
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How did he discover this
Chadwick studied the effect of bombarding a beryllium target with alpha particles, this showed there must be uncharged particles in the nuclei of atoms as well as positively charged protons. He called them neutrons.
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What is the atomic number of an atom
The number of protons inside in its nucleus. Its is also known as the proton number.
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What is the mass number of an atom
This is the number of protons plus nuetrons in its nucleus
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Who invented the mass spectrometer
F.W. Aston
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How does the mass spectrometer help scientists
This gave scientists an accurate method of comparing the relative masses of atoms and molecules
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Describe the key features of a mass spectrometer
1. The Gaseous sample from the inlet system
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Secondly...
2. The ionisation of the samle by bombardment with electrons or other methods
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Thirdly...
3. The mass analyser seperates ions by mass to charge ratio e.g. magnetic field or time of light
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Fourthly...
4. The ion detector give out an electrical signal which is then converted to a digital response that is then stored in the computer
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What state must the sample being analysed by a mass spectrometer be
Gaseous
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How do scientists convert something into the gaseous state
In some mass spectrometers a beam of high energy electrons bombards the atoms of the sample, this turns them into ions by knocking out one or more electrons
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How are mass spectrometers designed so the sample does not interfere with particles in the air
The mass spectrometer has a high vacuum
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What is the mass-to-charge ratio (m/z)
This is the ratio of the relative mass of an ion m, to its charge z, where z is the number of charges
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Describe the three types of mass spectrometers
The first type uses an electric field to accelerate ions into a magnetic field which then deflects the ions onto the detector
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The second type...
Accelerates ions and then seperates them by their flight time through a field-free region
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The third type known as a transmission quadrupole instrument
It varies the fiels in the instrument in a subtle way to allow ions with a particular mass-to-charge ratio to pass through to the detector at any one time
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What is an isotope
Atoms of the same element which have the same number of protons in the nucleus but a different number of neutron
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What is the standard isotope
Carbon-12
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Name a few ways in which isotopes are the same
- Same number of protons - Same number of electrons - Same atomic number - The same chemical properties
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Name a few ways in which isotopes are different
- Different numbers of neutrons - Different mass number - Different physical properties
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Define the relative atomic mass
The relative atomic mass of an element is the average mass of an atom of the element relative to one twelfth the mass of an atom of the isotope carbon-12
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What is the relative isotopic mass
This is the mass of one atom of an isotope relative to 1/12 the mass of an atom of the isotope carbon-12
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What is the equation for the relative atomic mass
Relative atomic mass = average mass of an atom of an element/ 1/12 x the mass of one atom of carbon-12
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What is the relative molecular mass
The relative masses of molecules, it is a sum of the relative atomic masses of all the atoms in its molecular formula e.g. O2 = 2 x Ar(O) = 2 x 16 = 32
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What is the relative formula mass
of a compound is the sum of the relative atomic masses of all the atoms in its formula e.g. Mr(Mg(NO3)2) = Ar(Mg) + 2 x [Ar(N) + 3 x Ar(O)] = 24.3 + 2 x (14 + 48) = 148.3
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When analysing a molecular compound, what does the peak ofof the ion with the highest mass indicate
It is usually the whole molecule ionised
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What can chemists deduce by interpreting the data from a mass spectrometer
- The isotopic composition of an element - The relative atomic masses of elements - The reative molecular masses of compounds
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How is chromatography and mass spectrometry used in chemical analysis
Chromatography is used to seperate the chemicals in an unknown mixture such as polluted water into water and the polluted item. The Mass spectrometry is used to detect and identify the seperated components
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Name one use of a mass spectrometer in real life
It is used to detect if olymic atheletes have been using performance enhancing drugs
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What is the ionisation energy
The energy needed to remove one electron from from each atom in one mole of gaseous atoms
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Explain another way scientists can determine the ionisiation energy of an atom
They can do this by using a spectroscope to study the light given out by atoms when heated in flames, the spectroscope shows up as many bright lines, heating up atoms which gives them enough energy to jump to higher energy levels
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What is an atomic energy level
They are energies of electrons in atoms, each electron has a specific energy level
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What is sheilding
it is an effect of inner electrons which reduces the pull of the nucleus on the electrons in the outer shell of an atom, because of shielding the electrons in the outer shell are attracted by an effective nuclear charge
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Section 4
Inorganic chemistry and the periodic table
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What is thermal decomposition
It is the name for a rection in which a compound decomposes on heating
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What happens when ypu heat hydrated compounds such as CuSO4.5H2O
They decompose fairly gently and give off water vapour
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Name a convenient strong acid
Dilute hydrochloric acid
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Name a convenient strong base
Sodium Hydroxide
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What happens when you add water to acids HCl --water--> ???
They produce H+ Ions HCl --water--> H+ + CL-
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What is an ionic equation
They describe chemical equations by showing only the reacting ion in solution while leaving out the spectator ions, ionic equations are balanced per atom, per charge
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What is a spectator ion
They are ions which are present in solution but take no part in the reaction
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Equation with spectator ions: Mg + (2H+) + (2Cl-) ---> (Mg^2+) + (2Cl-) + H2
Equation without spectator ions: Mg + (2H+) ---> (Mg2+) + H2
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All alkali's dissolve in water to produce what ion
Hydroxide ions
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When nuetralising an acid what is produced
A salt e.g. HCL + NaOH ---> NaCl + H2O [Without spectator ions: (H+) + (OH-) ---> H20] The respective ions of sodium and chlorine don't react
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What substance is used to test for the presence of calcium carbonate (any carbonate) in rocks
Hydrochloric acid is dripped onto the rock and if it is present it will fizz
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What is an ionic precipitation reaction
This is a reaction which produces a solid precipitate on mixing two solutions containing ions
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Whatis the best way to describe group 1 metals
They can be described as alkali metals, their compounds are widely used as chemical reagents
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How do we protect fresh metals from reacting with air and moisture
by keeping them in oil
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When talking about trends along the period table what is meant by trends
A trend describes the way in which a property increases or decreases along a series of elements or compounds. It describes the variations of properties down a group or across a period on the periodic table
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What trend can be described as you go down the group of elements on the periodic table
The charge of the nucleus increases, therfore, the number of filled inner shells increases, therefore, the atomic radius increases
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How can you describe the trend of the number of electrons in the inner shell
It is always one less than the number of protons in the nucleus
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How can you describe the sheilding effect as you go down the group
The sheilding effect of the inner electrons means that the effective nuclear charge attracting the outer electron is +1. As you go down the group the outer electron gets further away from the same effective nuclear charge and so they are held less st
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What happens when alkali metals react
They loses their single s electron from the outer shell, turning into ions e.g. Na+ this is their only oxidation state
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What makes alkali metals powerful reducing agents
They react by giving up electrons to form M+ ions
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What do metals react with water to form
All metls react with water to form Hydroxides MOH and hydrogen
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What is the trend of these reactions as you go down the group
The rate and the violence of the reaction increases
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What is a base
Bases are 'anti-acids' they are the chemical opposites of acids. Acids donate and give up hydrogen ions, base (e.g. oxide ions, hydroxide ions and carbonate ions) accept hydrogen ions
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What are the common physical properties of hydroxides
They are all white solids, soluble in water, forming alkaline solution, solubility increases down the group
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Why are hydroxides strong bases
because they are fully ionised in water, giving sloutions containing hydroxide ions
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What are the common physical properties of carbonates
They are all white solids, they form the general formula M2CO3, they dissolve in water and most of them do not decompose apon heating
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Why are solutions of these carbonates alkaline
because the carbonate ions remove H+ from the water molecules to form hydrogencarbonate and hydroxide ions that makes the solution alkaline. [Find out if carbonats are weak bases]
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What are the common physical properties of nitrates
White crystalline solids, MN03 formula, soluble in water
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How do sodium and potassium nitrate act when heated
Firstly they are stronger than other metal nitrates, they firstly start to melt then on stronger heating start to decompose giving off oxygen
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Why is lithium nitarte exceptional
when heated it decomposes to the oxide, nitrogen dioxide and oxygen
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Why are sodium and potassium used as chemical reagents
The ions of alkali metals are unreactive, so they act as spectator ions that take no part in the reaction when the reagents are used
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Secondly...
most sodium and potassium compounds are soluble in water including their hydroxles and their carbonates
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Thirdly...
Ions of alkali metals are colourless in aqueous solution so they dont interfere with the colour change. Sodium or potassium compounds are only coloured if the negative ion is coloured e.g. potassium chromate is yellow because the Cr04^2- ions are yel
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What is a method to detect some metal ions
Flame test/colours, they are useful in detecting group 1 metal ions
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What causes the colour to change during the flame test
Energy from the flame excites the outer electrons raising them to a higher energy level, the colour is emitted as the electron drops back to a lower energy level
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Wha are the flame colours of group 1 metal compounds
1.) Lithium: Bright red 2.) Sodium: Bright yellow 3.) Potassium: Lilac
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What family do group 2 elements belong to
Alkaline earth metals
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Name some forms of calcium carbonate
Chalk, marble and limestone
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What is dolomite a mixture of
it is a mixture of calcium and magnesium carbonates
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What is fluorspar a form of
Calcium flouride
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Unlike the equivalent of their group 1 compounds how can we describe their relationship with water
They are insoluble in water
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What is the difference between group 2 metals and group 1 metals
Group 2 metals are harder, denser and have higher melting temperatures
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Describe beryllium
It is a strong metal with a high melting temperature, it is less dense than transition metals such as iron, the element makes useful alloys with other metals
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How is magnesium manufactured
Magnesium is manufactured by the electrolsis of molten magnesium chloride from sea water or salt deposits
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Why is magnesium good for making alloys
Because it has a low density, the alloys which are strong for their weight are useful for car and aircraft manufacture
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Describe barium
Barium is soft, silvery-white metal
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Why i barium stored in oil
Because it is so reactive with air and moisture
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Decribe the trend of group 2 metals as you go down the group
The charge on the nucleus increases, the number of filled inner shells also increase, the atomic and ionic radii increase down the groupthe tendency to react and form ions increases down the group.
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continued...
The first and second ionisation energies decrease down the group, the sheilding effect increases down the group, the ionisation energies decrease down the group, the reactivity of each ion increases down the group
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Why is it harder to remove the third electron from the group 2 metals
This takes much more energy because the third electron has to be removed against the attraction of a much larger much more effective nuclear charge
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Why do group 2 metals have similar chemical properties
Because they have similar elctron structures with 2 electrons in the s orbital
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What are group 2 metals also known as
reducing agents
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What happens when you burn group 2 metals
they burn in oxygen on heating to form white, ionic oxides, consisting of M^2+ ions and 0^2- ions
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Why is magnisium used as fireworks and flares
Its burns very brightly in air with an intense white flame
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What happens when you burn calcium in air
It forms a red flame forming the white solid calcium oxide
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What elements burns in a similar ways to calcium
strontium
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What happens when you burn Barium in air
it produces a green flame to form a peroxide Ba02 which contains the peroxide ion 02^2-
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How can we describe the reactions of group 2 and group 1 metals with water
group 1 metals react more vigorously with water, the rate of reaction increases down the group7
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How does magnesium react with water
It reacts very slowly with cold water producing Mg(OH)2 and hydrogen, it reacts faster when heated in steam
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how does calcium react with water
calcium reacts with cold water to produce hydrogen and calcium hydroxide, Initially Ca(OH)2 and dissolves a little bit but the solubility is low so the solution becomes saturated and a white precipitate is formed
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How does barium react with water
barium reacts even faster with cold water and its hydroxide is more soluble
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write the equation for the metals that react with chlorine to make MCl2
M + Cl2 -> MCl2
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Who discovered electrons

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