Atomic Structure

Compounds are formed from elements by chemical reactions which always involve a formation of one or more new substances. They often include a detectable energy change. They are shown as symbols of the elements of which they were formed and chemical reactions are shown by word/symbol equations.

They consist of 2+ elements or compounds which ARE NOT chemically combined. Mixtures can be physically separated which involve NO chemical reactions which means NO NEW SUBSTANCES ARE MADE!

Methods of physical separation:

• simple distillation
• filtration
• crystalation
• chromatography
• fractional distilation

Once the electron was discovered the Plum Pudding Model was created which suggests that the atom is a ball of positive charge with negative electrons embeded in it. Because of this experiments suggested that the positive charge of any nucleus could be divided into smaller particles with equal charge and named it the proton.

The Plum Pudding Model was replaced by a nucleur model which was made after an Alpha Particle Scattering experiment concluded that the mass of an atom was concentrated at the charged nucleus. But then it was suggested that electrons orbit the nuceus at specific distances so the model was adapted by Neils Bohr.

The atomic number of an element is the number of protons it has. In an atom the number of electrons = the number of protons in the nucleus.

Name of particle                      Relative Charge

Proton                                         +1

Neutron                                         0

Electron                                       -1

The mass number = the sum of protons and neutrons in an atom. Almost all the mass of an atom is in the nucleus. Atoms of the same element can have a different number of neutrons. These atoms are called isotopes. Atoms have the radius of 0.1nm

An atom can be represented like this:

(Mass Number) 23

(Atomic Number) 11          Na

Name of particle               Relative Mass

Proton                                     1

Neutron                                   1

Electron                                 Very Small

It's an average value that takes account of the abundance of the isotopes of the element.

The electronic structure can be represented by numbers or diagrams. the amount of electrons on the outer shell can tell you what group the element is in on the periodic table.