An element is a substance in which all the atoms are the same
Where are elements shown?
Elements are shown in the Periodic table
How many elements are there?
There are around 118 elements
What is a compound?
A compound is a substance that contain two or more elements chemicallycombined
Describe the properties of compounds
The properties of compounds are usually different to the elements that they are made from
What is a mixture?
A mixture is a substance with different elements or compounds not chemically combined
Give an example of a mixture
An example of a mixture is sand and water as they are not chemically combined and can be separated by physical means
What is a molecule?
A molecule is a substance that has any elements chemically joined
What does a chemical formula tell you about a molecule?
A chemical formula tells the elements in a molecule and the number of atoms of each element
How is a chemical formula presented?
Each element symbol starts with a capital letter, if there is a second letter it is in lower case
Give an example of a chemical formula
What are state symbols?
State symbols show the physical state of the substance solid (s), liquid (l), gas (g), or dissolved in water (aq)
Name three properties of Metals
-Strong
-Good conductors of heat and electricity
-High melting and boiling points
Name three properties of Non-Metals
-Weak
-Bad conductors of heat and electricity
-Low melting and boiling points
State the four different ways of separating mixtures
Four different ways of separating mixtures are filtration, crystallisation, distillation or chromatography
Describe the process of filtration
Pour your mixture onto the filter paper, the liquid simply passes through the filter paper into the flask. The insoluble solid cannot pass through and so it stays on the paper
Describe the process of crystallisation
Use the method of filtration to filter off any excess solublesolid.Evaporate the mixture then transfer the hot mixture onto a dish. Crystals are formed when the mixture has cooled
Describe the process of simple distillation
First we evaporate the mixture by heating it, the dissolved solid then vaporises. These vapours condense in the condenser, the dissolved solid then flows into the beaker and liquid stays in the flask
Describe the process of chromatography
Take a strip of filter paper and draw a line on the bottom of the paper. Put a small drop of ink on the line, take a jar full of water up to the line and put the filter paper in. As the water moves up we see different colours on the paper these are the dyes in the ink
What were the early ideas of the structure of atoms?
Early ideas of the structure of atoms stated that they are tiny spheres that cannot be divided
What is the plum pudding model?
The plum pudding model is what scientists suggested is the structure of atoms is after the discovery of the electron
Describe the plum pudding model
The plum pudding model suggested that an atom is a ball of positive charge with negative electrons in embedded in it
Describe how Rutherford carried out the gold foil experiment
Rutherford took a piece of gold foil, he then fired tiny positive alpha particles at the gold foil
What did Rutherford observe in the experiment?
Rutherford observed that most of the particles when straight through the gold foil and sometimes the alpha particles bounce back of the gold foil
What did Rutherford discover from these observations?
Rutherford discovered that atoms are mainly empty space as most of the alpha particles went straight through the gold atoms and that the nucleus of the atom is very small as only a small number of alpha particles bounce back
Describe the structure of the nuclear model
The nuclear model states that most of an atom is empty space, in the centre is the nucleus which contains protons and neutrons around the edge we find electrons
What is the Relative mass and the relative charge of protons, neutrons and electrons?
Why do atoms have the same number of protons as electrons?
Because atoms have have no overall charge
What is an Ion?
An ion is a charged particle, it is possible to get positive or negative ions
What is an Isotope?
Atoms of the same element with different numbers of neutrons are called isotopes
What is the mass number of an element?
The mass number is the number on the top of an element it is the number of proton and neutrons combined
What is the atomic number of an element?
The atomic number is the number on the bottom it is number of protons in an atom, which is the same as the number of electrons
How many electrons can you fit in the first, second and third shells?
Shell 1 : 2 electrons
Shell 2 : 8 electrons
Shell 3 : 8 electrons
What is an Electronic structure?
A set of number to show the arrangement of electrons in their shells, eg. [2,6]
C2 The periodic table
What did John Newlands periodic table look like?
He arranged the elements in order of increasing atomic mass, he saw that every eighth element reacted in a similar way
What did Dmitri Mendeleev's periodic table look like?
He arranged the elements in order of increasingatomic mass, he switched the order of some elements to the fitted in the patterns of other elements. He left gaps for undiscovered elements
What does the modern periodic table look like?
Elements are arranged in order of atomic number, the elements are organised in groups and periods which have the similar properties