EquilibriumAcids and BasesRedoxOrganic

 Atomic Structure

  • Introduction
  • Electron Configuration
  • Ionization Energy
  • The three states of matter are known as solids, liquids and gases. 
    In solids, strong forces hold particles together. The particles are held together in fixed positions and they don’t move; so all solids have a definite shape and volume. The particles only vibrate. Increased temperature causes the particles to vibrate more and so solids expand when heated. Solids can’t be compressed and are usually dense.

  • In liquids, there are some attractive forces. The particles can move past each other and so liquids flow. Liquids don’t have a definite shape but the do have a definite volume. Liquids, like solids expand when heated. Liquids can’t be compressed because particles are still touching. They are quite dense but not as dense as solids.

  • In gases, there are no forces of attraction. The particles are moving all the time in a random way. There are lots of spaces between particles. Gases don’t have a definite shape or volume and so expand to fill any container. When the temperature is raised, particles move with greater speeds. So gases will either expand or increase in pressure. Gases can easily be compressed (a lot!) and they have very low densities.


The three particles contained within an atom are protons (+) ;  electrons (-)  and neutrons which have  (no charge). The nucleus contains protons and neutrons. Protons and neutrons have a unit mass of 1. Electrons have no mass.

Atomic structure




  • All atoms are electrically neutral because the number of protons equals the number of electrons.

  • Electrons are arranged in shells.

  • electron arrangement
  • Isotopes are atoms of the same element with the same numbers of protons but with different numbers of neutrons contained within their nucleus.

  • An element is a substance composed of only one type of atom

  • A compound contains more than one type of atom where the atoms are bonded together


  •  In ionic bonding, electrons are lost by metals and gained by non-metals. Ions formed are held together by electrostatic forces of attraction. Giant ionic crystal lattices are produced. These can also be called giant structures.


  • Ions are charged particles. Positive ions (cations) are formed when atoms lose electrons.

  • Negative ions (anions) are formed when atoms gain electrons.

  • Molecules are particles with no charge. In molecules of elements (eg. Chlorine, Cl2 ) atoms of the same type form covalent bonds. In molecules of compounds (eg. Water, H2O ) two or more atoms of different elements from covalent bonds.



First Ionization energy is defined as the energy needed to remove one mole of electrons from an atom in its gaseous state. it is expressed in KJ/mol.

From the below graph it can be seen that noble gases require high amount of energy to remove an electron from them and that is due to the presence of full outer shell and that the electrons are strongly attracted to the nucleus.

On the other hand, Alkali metals elements require the least amount of energy as they have only one outer electron which could be lost easily from the outer shell as it is far away from the nucleus.


Ionization Energy