Atoms and Elements

Lego Models

• There are 92 naturally occurring elements on the Earth
• Each element is made up of individual atoms, for example there are copper atoms inside a piece of copper
• All of these copper atoms are the same
• Sometimes separate atoms split into groups called molecules, oxygen is like this
• Sulphur has the largest groups of molecules: S8, this means 8 sulphur atoms are joined together in a ring molecule
• When different elements combine we get different materials called compounds
• Sulphur and oxygen combine together to create sulphur oxide, SO2
• A molecule has more particles than an atom
• The molecule gas ozone is written O3 this means that 3 oxygen atoms join together and create a molecule ring
• Atoms cannot be created or destroyed, they can be lost

Chemical Alphabet

• There are more than 100 elements but only 92 of them occur naturally, the rest are artificial
• A chemical symbol is a useful shorthand
• The names and symbols of some elements are named after a famous person or place
• A one-penny-piece is covered in copper metal and is about 2cm across
• Many secondary schools have 1000 students. We can calculate that there are about 75 million copper atoms making up a line on this penny then if each person counted one copper atom every second then 1000 students would need 24hours to count all of them

Getting Sorted

• The periodic table is divided into metals and non-metals
• Each kind of element has its own kind of properties
• There are some exceptions to this, graphite is a non-metal but conducts both heat and electricity
• The periodic table shows the elements in a special order:
• 1 is alkali metals, number 2 is allkaline earth metals, number 7 is halogens and number 8 is noble gasses
• Every element has its own atomic number
• The table is in order of atomic numbers
• Metals are all on one side and non-metals are opposite
• The vertical columns in the periodic tables are called groups
• elements in the same group have very similar characteristics
• At room temperature there are only 2 liquid elements: (metal) mercury and (non-metal) bromine
• Elements do melt if you heat them at high temperatures

All Mixed Up

• If you put appples and oranges together you get a mixture
• it is easy to separate this mixture
• there are only 3 metals that are attracted to a magnet: iron, cobalt and nickel
• Mixtures can be separated physically by using a magnet to seperate non-metals and metals
• Mixtures have just the properties of the things in the mixture meaning in iron sulphide only the sulphur fizzes in an acid
• Iron Sulphide is a mixture because it can be easily separated with a magnet
• Mixtures of elemnts can be made using different amounts of each one meaning they dont have to be equal, so ten parts iron and 1 part sulphur is still a mixture
• Most of the air we breathe is made up of nitrogen, a small part is made up of oxygen
• the moelcules in oxygen and nitrogen are paired up in twos
• We can separate the air by boiling it as we can let the gasses cool down until it is liquid, then boil it as nitrogen has a different boiling point to oxygen