Chemistry

Chemistry

1. An atom is the smallest possible particle of an element that can exist

   • The atom consists of a tiny, central nucleus surrounded by electrons
   • Structure of an atom

2. The nucleus

   • Contains protons and neutrons
     • Is positively charged because of protons
   • Heaviest Part of the atom (protons and neutrons have a much greater mass than electrons
   • Small in comparison to the rest of the atom

3. The electron shells

   • Electrons are arranged in energy levels around the nucleus
   • Electrons are fast moving
   • Once an energy level is full any extra electrons go into the next level
     • Atoms of different elements contain different numbers of protons. Atoms have no overall charge therefore the number of protons and electrons are the same
       • Electron configuration
         • It can tell us what group of the periodic table the element is in, judging by the outer shell
           • And also it can tell us what period its in, judging by the number of shells
           • Noble gases are the most unreactive elements in the periodic table, they appear at the end of each period. They are unreactive because they have a full outer shell of electrons. Other elements in the periodic table react with other elements to gain "more stable" noble gas configuration
     • The first energy level can hold 2 electons
       • The second and third can hold up to eight

4. Atomic number is the number of protons in the nucleus

   • The mass number is the number of protons and neutrons in the nucleus

5. Tons are atoms which have gained or lost electrons to obtain a full outer shell. Ions are chraged because electrons have a negative charge

   • Positive ions are called cations whereas negative ions are called anions

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