Periodicity

• The periodic table arranges the elements by proton number.
• All elements along a period have the same number of electron shells.
• All elements down a group have the same number of outer electrons, the number of which is indicated by the group number.
• Elements are classified into block within the periodic table that show electron configuration.
• s -block contain groups 1 and 2, p -block contains groups 3 to 0, d -block contain the transition metals, and f -block contains radioactive elements.
• Along a period, atomic radius decreases due to an increased nuclear charge for the same number of electron shells, causing the outer electrons to be pulled into the nucleus with greater attraction.
• Down a group, atomic radius increases due to the addition of an electron shell with each increment which increases shielding and distance.
• Along a period, ionisation energy increases as atomic radius decreases and nuclear charge increases, increasing the charge density.
• Down a group, ionisation energy decreases as nuclear attraction decreases due to increased shielding and distance.