Periodicity

What is periodicity

Repeating pattern/trends (of physical or chemical properties/reactions) in a period

What is the trend in atomic radius across a period

Atomic radius decreases,distance from nucleus to the outer shell decreases across a period because more protons and attraction similar shielding

What is the trend in nuclear charge across a period

Increases ,atomic number increases more protons and more attraction between nucleus and valence electrons so atomic radius decreases

Describe the trend in melting point across period 3

• Sodium,magnesium and aluminium MP increases,metallic bonds get stronger ,increasing +ve charge and increasing number of delocalised electrons so more attraction

• Silicon is macro molecular with tetrahedral structure so has strong covalent bonds which mean a lot of energy is required to break them

• Phosphorus,sulfur,chlorine and argon molecular substances MP depends on strength of van der waal forces,as sulfur is the biggest molecule (8) has higher MP

• Argon very low MP as it exists as an individual atom so has weak van der waals forces

What is the trend in first ionisation energy across period 3

First IE increases because of increased attraction between outer shell electrons and nucleus and increasing atomic number.similar shielding