Chemistry Atomic Structure (Subatomic Particles ( image, Proton - Mass 1,…
Chemistry Atomic Structure
A mixture consists of two or more elements or compounds not chemically joined.
This technique separates substances that are insoluble in a solvent from those that are soluble.
Example = Filtering a mixture of sand, salt and water to collect the sand.
This technique separates a soluble substance from a solvent by heating.
Example = Crystallisation of sodium chloride from salt solution.
This technique separates a liquid from a mixture by evaporation follow by condensation.
Example = Obtaining water from sea water
This technique differs from distillation only in that it separates a mixture into different parts, known as fractions.
Obtaining ethanol from a mix of ethanol and water.
This technique separates small amounts of dissolved substances by running a solvent along absorbent paper.
Example = Separating the different colours out of ink.
Atoms, Elements and Compounds
All substances are made of atoms that cannot be broken down. It is the smallest part of an element.
Elements are only made of one atom. Each element has its own symbol. E.g Na is Sodium
Compounds contain more than one type of atom. Naming compounds - 2 elements =
. 2 ore more elements =
Development of Atomic Model
Dalton - Atoms can't be divided
JJ Thompson discovered electrons - plum pudding model.
Geiger Marsden the Nuclear Model of the Atom
Bohr - electrons in shells
Chadwick - the neutron
Proton - Mass 1, Charge +, Location : Nucleus
Neutron - Mass 1, Charge 0, Location : nucleus
Electron - Mass Very Small, Charge -, Location : shells
Mass Number = Number of protons and neutrons
Atomic number = number of protons
Number of protons(+) = Number of Electrons(-)
Number of neutrons = mass number - atomic number
Atoms of the same element with different mass numbers(numbers of neutrons)
The energy level closest to the nucleus can hold 2 electrons
The second energy level can hold 8 electrons
Electrons are found in energy level surrounding the nucleus
The third energy level can hold 8 electrons
Electrons fill the lowest energy level first, then the next one etc.
When atoms react, they are trying to achieve a full Outer Energy level of electrons before they are stable.