C4a- Atomic Structure

C4a- Atomic Structure

1. Atom

   • Nucleus is made up of Protons and Neutrons
   • Electron Charge: -1 and Electron Mass: 0.0005 (zero)
   • Proton Charge: +1 and Proton mass: 1
   • Neutron Charge: 0 and Neutron Mass: 1
   • An atom is neutral in terms of Sub atomic Particles because it contains equal numbers of electrons which are negatively charged and protons which are positively charged.
   • Atoms have a radius of 10-10 m Atoms have a mass of 10-23g

2. Isotopes

   • They are varieties of an element that have the same atomic number but different mass numbers so they have different number of neutrons
   • MASS NUMBER: Number of NEUTRONS AND PROTONS. This is the top number
   • ATOMIC NUMBER: Number of Protons OR ELECTRONS. this is the bottom number
   • The Number of Neutrons is the mass number minus the atomic Number

3. Ions

   • If the CHARGE on the atom if 2-, then the number of electrons ADDED is 2. If the CHARGE on an atom is 2+, then the number of electrons TAKEN AWAY is 2

4. Arrangement on elements in the periodic table

   • They are arranged in groups according to how many electrons are in its outer shell. They are arranged in periods according to how many shells the element has

5. How can an element be deduced from its electronic structure?

   • It can be deduced because the period shows how many shells it has and the Group shows how many electrons are in its outer shell.
   • Calcium: 2,8,8,2

6. History of the development of the atom

   • At the start of the 19th Century John Dalton discovered All matter was made from atoms , Atoms cannot be made or destroyed , All atoms of an element are identical and Different Elements contain different types of atoms
   • 1897 J.J. Thomson discovered that Atoms contain even smaller subatomic particles called electrons
   • 1913 Niels Bohr discovered Electrons move in fixed orbits or shells around the nucleus
   • The theory changed as new evidence was found Science explanations are provisional but more convincing when predictions are later confirmed

7. Significance of the works of the scientists in the development of the theory of the atomic structure

   • Unexpected results (e.g. Geiger and Marsden’s experiment) led to the theory of the nuclear atom: Alpha particles were fired at a thin sheet of gold and found that some were deflected. This introduced the fact that the atom has a nucleus with an overall positive charge because Alpha particles were positive and therefore they would repel causing deflection