Atomic structure

• An element is a substance made up of 1 type of atom. They are in the periodic table of elements.They cannot be broken down into anything simpler.

• A compound is a substance which is made up of 2 or more types of atoms chemically bonded together. They can be chemically broken down into something simpler.

• A mixture contains 2 or more substances which are not chemically bonded together. They are easy to separate by physical means.

• Atoms are tiny.

• They make up everything in the universe.

• An atom includes the NUCLEUS which is at the center of the atom.
• Atoms are nuetral i.e. they hav no overall charge.
  

Atoms are made up of 3 sub atomic particles. :

• PROTONS

• NUETRONS

• ELECTRONS

• The protons and neutrons are in the nucleus.

• The mass of protons (1) and the mass of neutrons (1) make up the total mass of the atom.

• Protons have a possitive charge ( 1+ ). Neutrons are a nuetral (0).
  

• Electrons have a negative charge (-1).

• The number of electrons are equal to the number of protons.

• outside the nucleas are energy levels/ energy shells which hold the electrons.

• The electrons circle the nucleus.

• The mass = Number of neutrons + Number of protons

• Number of Neutrons = Mass - Number of protons

• Number of Electrons = Number of protons

mass number 23

Na

Proton number 11

• Atoms are neutral i.e will have no overall charge as the number of protons is equal to the number of electrons therefore the positive and negative charges are cancelled out

• The nucleus of an atom is very dense as all the mass of the atom is in the neucleus and the nucleus is very small.

The energy levels can only hold a certain amount of electrons in them.

energy level 1 = maximum 2 electrons

energy level 2 = maximum 8 electrons

energy level 3 = maximum 8 electrons

• Some elements can have more than one mass number.
  

• elements like this are called isotopes;

• they have the same number of protons but different numbers of neutrons.

• they are chemically identical.