Foundation and higher tiers
Elements are simple substances composed of only one type of atom. The periodic table lists all known elements. Each element in the periodic table has its own symbol. It is important that you learn the names and symbols for the first 20 elements in the periodic table.
Why not do a little research on some of the
elements and find out about their properties and the people who discovered them? The chemical symbols
for the elements often come from the names of the scientists who discovered them, or from the names of
gods or astronomical objects e.g. the table below could start off your internet search, you just need to add
to it, perhaps add a few additional columns to summarise any additional information you find out.
Some elements have only a single letter for their symbol, e.g. oxygen is given the symbol O. It is a capital O and not a lowercase o. This is true for all single letter symbols in the periodic table. If the symbol is made up of 2 letter, e.g. sodium, symbol Na. The first letter is always capitalized and the second is always lowercase, so sodium is never NA or na, always Na. Iron is Fe, NEVER fE or FE.
|element||chemical symbol||Where its name comes from|
|strontium||38 Sr||Named after village of Strontian, Scotland|
|helium||2 He||Helios, god of the Sun.|
|hafnium||72 Hf||Hafnia, Latin for Stockholm.|
|tellurium||52 Te||Tellus, Latin for Earth.|
|curium||97 Cm||Pierre and Marie Curie.|
|mendelevium||101 Md||Dimitri Mendeleev.|
|thorium||90 Th||Norse god Thor.|
|titanium||22 Ti||Titans, Greek mythology.|
||Vanadis(Freya) Norse Goddess.|
|silver||47 Ag||Latin name Argentum.|
|tungsten||74 W||Mineral wolframite, which contains high concentration of tungsten.|
Compounds are formed when two or more elements chemically join together. The atoms in the compound are held together by chemical bonds. You will learn about three types of chemical bonds in your GCSE chemistry course, these are covalent, ionic and metallic bonds. The images below show 3 common compounds which you will meet in your GCSE course. These compounds contain only non-metal atoms, compounds like this are called covalent compounds. The 3 compounds are all molecular, this means they consist of small groups of atoms.
Compounds have very different properties from the elements that make them up, as an example
consider the reaction shown in the image opposite between iron and sulfur. Iron is a dull
grey magnetic metal and sulfur
is a bright yellow non-metallic solid. If a mixture of iron and sulfur are heated strongly for a few minutes
in a test-tube then a dull red glow is seen as the reaction takes place. The compound formed is called
iron sulfide. A word equation for the reaction is:
Compounds formed between metals and non-metals are called ionic compounds. These compounds are made up of
Ions are charged atoms formed when atoms lose or gain
electrons. Metals tend to lose
electrons when they react and form ions with a positive charge,
non-metals tend to gain electron when they react. Ionic compounds are not molecular, that is their structure does
is not made up of small groups of atoms, instead they have giant structures of ions called ionic lattices. The physical properties,
such as melting, boiling points and whether it conducts electricity tend to be determined by the type of structure a compound has.
The diagram shows a particle picture for the reaction of iron and sulfur to form iron sulfide. You can see that all the iron atoms and all the sulfur atoms are the same, this obviously means that they are elements. However once they react to form the compound iron sulphide the iron and sulfur atoms join with each other. Iron sulfide has a giant ionic lattice structure. Only a few iron and sulphur ions are shown but in reality the structure would consist of billions of ions all joined together.
This is very different from the small molecular structure shown for covalent compounds above. Ionic compounds have very different chemical and physical properties from covalent compounds largely due to differences in their structures and the types of bonds holding the particles together. You will learn more about this when you revise the section on bonding and structures.
Most compounds end in the letters -ide, this tells us that the compound is made up of only 2 elements. Some compounds end in the letters -ate, this means the compounds have more than 2 elements and one of them is oxygen. e.g.
|sodium chloride||sodium and chlorine|
|magnesium oxide||magnesium and oxygen|
|carbon dioxide||carbon and oxygen|
|sodium carbonate||sodium, carbon and oxygen|
|calcium nitrate||calcium, nitrogen and oxygen|
|calcium hydroxide||calcium, hydrogen and oxygen|
When element react to form compounds we can show this chemical reaction as a word equation, e.g. hydrogen gas burns in air (oxygen) to form water (hydrogen oxide). A word equation for this reaction is shown below.
Here the reactants are hydrogen and oxygen and the compound formed is called the product of the reaction. Compounds are named as described above. Here the last 4 letters of the non-metal oxygen (ygen) are replaced by -ide.