Periodicity

• Periodicity: The repeating pattern or trends in the properties of elements.
• Across a period, the atomic radius decreases as the number of protons increases hence the nucleus pulls on the outermost electron more strongly and across a period elements have similar shielding
• First ionisation energy increases across a period with the exception when an electron first enters a p orbital as that has extra shielding from s orbitals and the first instance when 2 electrons share a p orbital due to repulsion between like charges
• The 2 elements that you have to be wary of when writing their electron configuration is copper and chromium as you put their 4s orbitals in their 3d orbitals instead