An atom is the smallest part of an which still has the proporties of that element.
The three sub-atomic particles are protons neutrons and .
Electrons are and orbit the nucleus.
Protons are and are to be found in the with the neutral neutrons.
The atomic number is the number of in the nucleus.
The mass number of an element is the total number of protons and neutrons in the .
are atoms of the same element which have different numbers of neutrons.
An element is made up of only one type of .
There are over 100 different .
The Table is a list of all the elements.
K is .
Na is .
are made up of two or more elements chemically combined.
A compound has different to the elements it is made up of.
Nitrogen and are examples of diatomic molecules.
The Periodic table shows elements in order of increasing number.
Groups are e.g. group 1, the alkali metals.
Periods are e.g. period 1 only has elements in it.
Group 1 elements are very as they only have one in their outer shell and they want to it. The are low , when cut, stored under , reacts with water, produces gas, turns the water , turns litnmus paper , are easily , have low melting points and conduct as they are metals.
Sodium reacts with water to form sodium hydroxide and .
Group 2 are the earth metals e.g. magnesium.
Group 7 are the e.g. chlorine gas.
Group 8 are the noble gases. They are very .
The elements can be divided into and non-metals.
Only two elements are liquids at room temperature; bromine and .