Fundamental Ideas

Fundamental Ideas

1. Each element is made from one type of atom

   • Atoms have a tiny nucleus surrounded by electrons
     • The nucleus contain protons and neutrons.
       • An atom has no charge are the number of protons and electrons are the same
   • When two or more elements join, a compound is formed
   • The atomic number of an element is the number of protons (and electrons) an element has
     • The mass number is the total number of particles in the nucleus of the atom, so it is the number of protons plus the number of neutrons

2. Group 1 elements are highly reactive as their outer shell only has 1 electron, group 0 is the most stable

   • Electrons occupy the lowest energy levels first and get higher the further out they go
     • The first shell has 2 electrons and the other shells can hold up to 8 electrons
       • All the elements in the same group have the same number of electrons in the outer shell (with the highest energy