Atoms, elements, compounds, mixtures -
- An atom is the smallest part of an element that can exist.
- An element is a substance that is only made from one type of atom.
- Elements can exist as single atoms, molecules (particle with 2 or more atoms chemically
bonded) or in a giant structure.
- A compound contains two or more DIFFERENT elements chemically combined in fixed
proportions so it can be written as a formula.
- C is carbon, Ca is calcium, H2 is hydrogen, NaCl is sodium chloride, MgF2 is magnesium
fluoride, Al2O3 is Aluminium Oxide, CO2 is carbon dioxide, AgNO3 is silver nitrate. The ‘ide’
tells us it is a compound. The ending ‘ate’ tells us oxygen is present and there is more than one
non-metal.
- A mixture consists of two or more elements or compounds not chemically combined together.
So, the chemical properties of each substance are unchanged.
Separating Mixtures -
- In a mixture chemical elements aren’t joined together so can be separated with physical
methods.
- Filtration separates an insoluble solid from a liquid. Set up filter paper in a filter funnel passing
through to a beaker of flask. Pour the mixture, solid particles too large, liquid passes through.
Solid left behind is residue, liquid in beaker is filtrate.
- Crystallisation (or evaporation) separates a soluble solid from a liquid. Place a solution in an
evaporating basin on and stand and heat with a bunsen burner. The water evaporates leaving
behind solid crystals.
- Simple distillation separates a liquid solvent from a dissolved solution. A solvent is the liquid
that dissolves it. Set up the solution (e.g. salty water) in a flask fitted with a condenser so any
gases produced travel through. Heat with a bunsen burner, evaporates and vapours pass
through condenser. Condenser surrounded by cold water so particles condensate and turn back
into liquid form. Water droplets are collected in a beaker. The salt is left behind in the flask. This
could be used for purifying salty water to become drinkable.
- Fractional distillation separates two or more liquids that have different boiling points. For
example, water and ethanol. A fractionallising column is added to slow down rising gases. This
is heated with an electric heater as ethanol is flammable. It is important the temperature is
controlled so the liquids evaporate separately. Ethanol passes through the condenser first. After
the temperature can be increased so water can be distilled. Often used to purify or strengthen
alcohol. To check if the substance is pure, measure boiling points. Ethanol 78C, water 100C.
- Paper chromatography separates dissolved substances from each other. Draw a pencil line
onto filter paper, spots of ink/dye at fixed intervals. Add a small amount of solvent (e.g. water) to
dissolve ink. Starts at a level below line drawn. Paper lowered in and solvent travels up through
the paper. Different coloured substances spread apart. A pure substance will only produce one
spot, a mixture produces multiple. More soluble solids travel further up the paper. Used in
chemical analysis such as drug testing, crime scene investigation, etc.
,
Scientific Models of the Atom -
- The model of the atom has developed over time.
- In the Greek era atoms were thought to be tiny sphere that could not be divided.
- Later, the discovery of the electron led to the plum pudding model. It was thought to be a ball
of positive charge with negative electrons embedded in it.
- Rutherford did the scattering experiment where alpha particles were beamed at a thin layer of
gold foil, a few atoms thick. They expected them to travel through (plum pudding), however
some a few particles were deflected in lots of directions, disproving this model. It showed the
positive charge wasn’t spread throughout the atom and was concentrated in a tiny area in the
middle (nuclear model).
- Bohr suggested that electrons orbited at specific distances away from the nucleus in energy
levels (shells).
- We realised the positive charge was divided into protons instead of one single space. There
were as many protons as neutrons giving it a neutral charge.
- In 1932 Chadwick discovered neutrons (mass but no charge, found in nucleus).
Atomic structure -
- The radius of an atom is 0.1nm (nanometers). The nucleus is a 1/10,000 the size of an atom.
The nucleus is where nearly all of the atom’s mass is found.
- Subatomic particles are neutrons, protons and electrons. Neutrons have no charge.
- Particles in the nucleus are fixed in place, but electrons are always moving. The layers are
shells.
- The atomic number (bottom) tells us how many protons OR electrons there are as they cancel
out the charge to become neutral.
- The relative atomic mass (top) tells us the mass of the nucleus (number of protons AND
neutrons).
Relative atomic mass -
- An isotope is an atom wit the same number of protons but different number of neutrons (mass
number different). If same number of protons, same elements.
- The relative atomic mass is the weighted mean mass of an element, takes into account all
isotopes of an element and their relative abundance.
- Rf = (mass of isotope x abundance) / 100. Abundance is a percentage. For example
(35x75)+(37x25) / 100. Your answer should also be between the two masses you’re given.
Electronic structure -
- Each small can have a maximum number of electrons. Shells max: 2, 8, 8, 8. You need to be
able to draw the first 20 elements.
The periodic table -
- The periodic tables shows about 110 different elements. They are arranged based off of
atomic number. Their reactions depend on their number of electrons (number of electrons on
outer shell).
, - The first versions of the periodic table ordered them in their atomic weights.
- Early scientists tried to group elements in triads according to similar reactivity.
- Newlands discovered the “Law of Octaves” showing the properties of elements repeated
every 8 elements. However it was still inconsistent.
- Mendeleev realised there were many undiscovered elements and left gaps for them. He
ordered by atomic weight still and grouped them. He predicted the properties of unknown
elements correctly, them later being discovered.
- Elements are ordered in columns known as groups. Groups have the same number of
electrons in the outer shell and do similar reaction / has similar properties.
- Rows do different chemical reactions. The rows are known as ‘periods’ as properties repeat
periodically. Members of the same period have the same number of electron shells.
- Metals are usually solid, hard and shiny. They can be shaped and bended usually. Non-metals
are gases or liquids (or solids with low melting points). Metals are found on the left and middle,
non-metals found in top right. Staircase going down from above aluminium.
Group 0 – The Noble Gases -
- Includes helium, neon, argon, krypton, xenon, radon.
- Noble gases have full outer shells of electrons so are stable. They don’t need to gain or lose
electrons so are very unreactive/inert and don’t form molecules (exist as single atoms).
- Properties: They are colourless gases with low boiling points.
- As you go down the group, the atomic mass increases meaning the density and boiling point
increases (more energy to break atoms apart).
- They have a very stable electron configuration.
Group 1 – The Alkali Metals -
- Include lithium, sodium, potassium, rubidium, caesium.
- All have 1 electron on their outer shell, so when they react they need to lose it to gain a full
outer shell and become stable. They become +1 ions (as electrons have a negative charge, so
have more protons than electrons so overall positive charge).
- They have low densities so can float on water. They are soft (can be cut with a knife). They
are shiny but only when recently cut as quickly react with oxygen in air making them dull.
- Very reactive, reactivity increases down the group. This is because the attraction to the
nucleus is less as it is further away (more shells), so easier to lose an electron. Opposite
charges attract, electrons attracted to protons in nucleus.
- React with oxygen. For example, lithium and oxygen combine to form lithium oxide (Li2O).
Lithium has a positive charge, oxygen has a -2 charge and all compounds have to have a
neutral charge.
- When group one metals react with oxygen, at room temp. they change from shiny to a dull
white. If heated, they burn vigorously releasing a lot of heat and smoke and forming a white
smoke.
- Group 1 oxides are readily soluble in water to form colourless solutions (metal hydroxides).
- React with chlorine and other halogens. Sodium and chlorine reacts to form a metal chloride
(2NaCl). Sodium is +1 (loses an electron), chlorine is -1 (gains an electron). Reaction would be
very vigorous seeing bright light and heat. The product is a metal chloride (a white solid known
- An atom is the smallest part of an element that can exist.
- An element is a substance that is only made from one type of atom.
- Elements can exist as single atoms, molecules (particle with 2 or more atoms chemically
bonded) or in a giant structure.
- A compound contains two or more DIFFERENT elements chemically combined in fixed
proportions so it can be written as a formula.
- C is carbon, Ca is calcium, H2 is hydrogen, NaCl is sodium chloride, MgF2 is magnesium
fluoride, Al2O3 is Aluminium Oxide, CO2 is carbon dioxide, AgNO3 is silver nitrate. The ‘ide’
tells us it is a compound. The ending ‘ate’ tells us oxygen is present and there is more than one
non-metal.
- A mixture consists of two or more elements or compounds not chemically combined together.
So, the chemical properties of each substance are unchanged.
Separating Mixtures -
- In a mixture chemical elements aren’t joined together so can be separated with physical
methods.
- Filtration separates an insoluble solid from a liquid. Set up filter paper in a filter funnel passing
through to a beaker of flask. Pour the mixture, solid particles too large, liquid passes through.
Solid left behind is residue, liquid in beaker is filtrate.
- Crystallisation (or evaporation) separates a soluble solid from a liquid. Place a solution in an
evaporating basin on and stand and heat with a bunsen burner. The water evaporates leaving
behind solid crystals.
- Simple distillation separates a liquid solvent from a dissolved solution. A solvent is the liquid
that dissolves it. Set up the solution (e.g. salty water) in a flask fitted with a condenser so any
gases produced travel through. Heat with a bunsen burner, evaporates and vapours pass
through condenser. Condenser surrounded by cold water so particles condensate and turn back
into liquid form. Water droplets are collected in a beaker. The salt is left behind in the flask. This
could be used for purifying salty water to become drinkable.
- Fractional distillation separates two or more liquids that have different boiling points. For
example, water and ethanol. A fractionallising column is added to slow down rising gases. This
is heated with an electric heater as ethanol is flammable. It is important the temperature is
controlled so the liquids evaporate separately. Ethanol passes through the condenser first. After
the temperature can be increased so water can be distilled. Often used to purify or strengthen
alcohol. To check if the substance is pure, measure boiling points. Ethanol 78C, water 100C.
- Paper chromatography separates dissolved substances from each other. Draw a pencil line
onto filter paper, spots of ink/dye at fixed intervals. Add a small amount of solvent (e.g. water) to
dissolve ink. Starts at a level below line drawn. Paper lowered in and solvent travels up through
the paper. Different coloured substances spread apart. A pure substance will only produce one
spot, a mixture produces multiple. More soluble solids travel further up the paper. Used in
chemical analysis such as drug testing, crime scene investigation, etc.
,
Scientific Models of the Atom -
- The model of the atom has developed over time.
- In the Greek era atoms were thought to be tiny sphere that could not be divided.
- Later, the discovery of the electron led to the plum pudding model. It was thought to be a ball
of positive charge with negative electrons embedded in it.
- Rutherford did the scattering experiment where alpha particles were beamed at a thin layer of
gold foil, a few atoms thick. They expected them to travel through (plum pudding), however
some a few particles were deflected in lots of directions, disproving this model. It showed the
positive charge wasn’t spread throughout the atom and was concentrated in a tiny area in the
middle (nuclear model).
- Bohr suggested that electrons orbited at specific distances away from the nucleus in energy
levels (shells).
- We realised the positive charge was divided into protons instead of one single space. There
were as many protons as neutrons giving it a neutral charge.
- In 1932 Chadwick discovered neutrons (mass but no charge, found in nucleus).
Atomic structure -
- The radius of an atom is 0.1nm (nanometers). The nucleus is a 1/10,000 the size of an atom.
The nucleus is where nearly all of the atom’s mass is found.
- Subatomic particles are neutrons, protons and electrons. Neutrons have no charge.
- Particles in the nucleus are fixed in place, but electrons are always moving. The layers are
shells.
- The atomic number (bottom) tells us how many protons OR electrons there are as they cancel
out the charge to become neutral.
- The relative atomic mass (top) tells us the mass of the nucleus (number of protons AND
neutrons).
Relative atomic mass -
- An isotope is an atom wit the same number of protons but different number of neutrons (mass
number different). If same number of protons, same elements.
- The relative atomic mass is the weighted mean mass of an element, takes into account all
isotopes of an element and their relative abundance.
- Rf = (mass of isotope x abundance) / 100. Abundance is a percentage. For example
(35x75)+(37x25) / 100. Your answer should also be between the two masses you’re given.
Electronic structure -
- Each small can have a maximum number of electrons. Shells max: 2, 8, 8, 8. You need to be
able to draw the first 20 elements.
The periodic table -
- The periodic tables shows about 110 different elements. They are arranged based off of
atomic number. Their reactions depend on their number of electrons (number of electrons on
outer shell).
, - The first versions of the periodic table ordered them in their atomic weights.
- Early scientists tried to group elements in triads according to similar reactivity.
- Newlands discovered the “Law of Octaves” showing the properties of elements repeated
every 8 elements. However it was still inconsistent.
- Mendeleev realised there were many undiscovered elements and left gaps for them. He
ordered by atomic weight still and grouped them. He predicted the properties of unknown
elements correctly, them later being discovered.
- Elements are ordered in columns known as groups. Groups have the same number of
electrons in the outer shell and do similar reaction / has similar properties.
- Rows do different chemical reactions. The rows are known as ‘periods’ as properties repeat
periodically. Members of the same period have the same number of electron shells.
- Metals are usually solid, hard and shiny. They can be shaped and bended usually. Non-metals
are gases or liquids (or solids with low melting points). Metals are found on the left and middle,
non-metals found in top right. Staircase going down from above aluminium.
Group 0 – The Noble Gases -
- Includes helium, neon, argon, krypton, xenon, radon.
- Noble gases have full outer shells of electrons so are stable. They don’t need to gain or lose
electrons so are very unreactive/inert and don’t form molecules (exist as single atoms).
- Properties: They are colourless gases with low boiling points.
- As you go down the group, the atomic mass increases meaning the density and boiling point
increases (more energy to break atoms apart).
- They have a very stable electron configuration.
Group 1 – The Alkali Metals -
- Include lithium, sodium, potassium, rubidium, caesium.
- All have 1 electron on their outer shell, so when they react they need to lose it to gain a full
outer shell and become stable. They become +1 ions (as electrons have a negative charge, so
have more protons than electrons so overall positive charge).
- They have low densities so can float on water. They are soft (can be cut with a knife). They
are shiny but only when recently cut as quickly react with oxygen in air making them dull.
- Very reactive, reactivity increases down the group. This is because the attraction to the
nucleus is less as it is further away (more shells), so easier to lose an electron. Opposite
charges attract, electrons attracted to protons in nucleus.
- React with oxygen. For example, lithium and oxygen combine to form lithium oxide (Li2O).
Lithium has a positive charge, oxygen has a -2 charge and all compounds have to have a
neutral charge.
- When group one metals react with oxygen, at room temp. they change from shiny to a dull
white. If heated, they burn vigorously releasing a lot of heat and smoke and forming a white
smoke.
- Group 1 oxides are readily soluble in water to form colourless solutions (metal hydroxides).
- React with chlorine and other halogens. Sodium and chlorine reacts to form a metal chloride
(2NaCl). Sodium is +1 (loses an electron), chlorine is -1 (gains an electron). Reaction would be
very vigorous seeing bright light and heat. The product is a metal chloride (a white solid known
