1. Physical periodicity The physical properties of elements repeat themselves in a regular pattern from one period to the next.

2. Periodicity of atomic radius The atomic radius is defined as “half the distance between two co-valently bonded atoms.” Plot atomic radius against atomic number for the elements of period 3. Explain the trend. NaMgAlSiPSClAr 0.156 (nm) 0.1360.1250.1170.1100.1040.0990.192

3. Periodicity of atomic radius Generally the radius decreases along the period. As the number of protons in the nucleus increases. Electrons are in the same shell, so shielding is similar. So electrons are more strongly attracted to the nucleus and the atom “contracts”. Inert gases have a much higher atomic radius than expected as they already have a full shell and are reluctant to form covalent bonds.

4. Periodicity of melting point (and boiling point). Plot the MP/BP against atomic element and explain the trend across period 3. NaMgAlSiPSClAr MP o C 98650660141044119-101-189 BP o C 890112024502680280445-34-186

5. Periodicity of melting point Strong metallic bonds so high MPs. C and Si, strong covalent bonds in giant lattice so even higher MPs. Weak van der Waals in simple covalent or atomic lattices so low MPs.

6. Periodicity of conductivity Explain the tend in conductivity across period 3.(Arbitary units.) NaMgAlSiPSClAr 1016384----

7. Periodicity of conductivity Metals, with delocalised electrons so good conductors. Non metals, insulators. Silicon, semi- conductor Graphite – conductor