Atomic Structure

Atomic Structure

1. Sub-Atomic particles

   • The smallest amount of an element which still behaves like an element is an atom
   • Each element has its own unique type of atom
   • Atoms are made up of smaller sub-atomic particles
     • The three main particles are protons, neutrons and electrons
       • These particles are small and have very little mass. There masses can be compared using a relative scale there charge can be compared in the same way
       • Proton and Neutron have the same mass
         • Protons and neutrons are found in the centre of the atom called the nucleus
           • The electrons form a series of shells around the nucleus
       • Protons and electrons have equal but opposite charges

2. Atomic number and mass number

   • To describe the number of protons, neutrons and electrons in an atom two numbers are used
     • atomic number
       • The number of protons which equals the number of electrons
     • mass number
       • the number of protons + neutrons

3. Isotopes

   • Atoms of the same element with the same number of protons and electrons but different number of neutrons
   • Isotopes have the same chemical properties but slightly different physical properties

4. Relative atomic mass

   • Atoms are too light to be weighed so relative atomic mass is used as a scale
   • The average mass of an atom of an element