C1 - Atoms

C1 - Atoms

1. Atoms + Elements

   • Elements
     • All Substances are made of Atoms
     • An individual atom is too small to see but everything around us contains many atoms
     • An Element is a substance that is made of only one sort of atom. eg. Oxygen is an element because it only contains oxygen atoms
   • Chemical Symbols
     • There are about 100 different elements
     • Atoms of each element are given a chemical symbol
     • Each symbol starts with a capital letter, usually followed by a lower case letter
       • eg. N represents a Nitrogen Atom but Na a Sodium Atom
     • Elements are shown in Periodic Table
   • Periodic Table
     • Each vertical column have group numbers + contain elements with similar properties
     • Metals on the left
     • Non-metals on the right
   • Atoms have a central nucleus made of positively charged protons + neutral neutrons
     • It is surrounded by negatively charged electrons

2. Particles in Atoms

   • Protons, Neutrons + Electrons are called Subatomic Particles
     • You can work out how many of each type of Subatomic Particle an atom has from its atomic number + mass number
   • Atomic Number
     • Number of protons in an atom of an element is called its Atomic Number
     • Atoms of different elements have different numbers of protons
       • No two elements can have same atomic number
   • Number of Electrons
     • Atoms have no overall charge
       • This is because the number of electrons in an atom is the same as the number of protons
     • Mass Number - Atomic Number
   • Mass Number
     • Total number of protons + neutrons in an atom is called its Mass Number
   • Diagrams of Atoms
     • These diagrams make it easier ti work out how many Subatomic Particles there are

3. Electronic Structure

   • Energy Levels
     • Electrons in an atom occupy different Energy Levels around the nucleus
     • Each electron in an atom is at a particular energy level
     • Electrons occupy the lowest available energy levels
   • Shells
     • Energy Levels are also called Shells
       • The Innermost Shell is the lowest energy level
       • The Outer Shell is the highest occupied energy level
   • Writing Electronic Structure
     • Different Energy Levels can contain different numbers of electrons
     • 1st Energy Level - 1 or 2 2nd Energy Level - up to 8 3rd Energy Level - up to 8
       • eg. Sodium has 11 electrons
         • 2,8,1
     • Column Number = Number of electrons in Outer Shell

4. Electronic Structure + Groups

   • Atoms of elements in a group in the period table have the same number of electrons in Outer Shell
     • This gives the elements similar chemical properties
   • Group 1 (Alkali Metals)
     • Elements in Group 1 include Lithium, Sodium + Potassium
       • Atoms all have just one electron in Outer Shell
     • Reactions with oxygen
       • Elements burn vigorously in oxygen to produce solid metal oxides
     • Reactions with Water
       • Elements react vigorously with water to produce hydrogen gas, and metal hydroxides that dissolves to form alkaline solutions
   • Group 0 (Noble Gases)
     • Elements in Group 0 include Helium, Neon + Argon
       • Outer Shells are Full
     • Helium has 2 electrons its outer shell
     • All the others have 8 in their outer shell

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