physical properties of period 3 elements

atomic radius _____ across a period

decreases

why does atomic radius decrease?

number of protons increases, positive charge of nucleus increases, electrons are pulled closer to the nucleus, making atomic radius smaller

melting points ____ and then ____

increase, decrease

why does na, mg, al melting points increase

the metallic bonds get stronger because the metal ions have an increasing positive charge, increasing the number of delocalised electrons

why does silicon have a high melting point?

macromolecular with a tetrahedral structure, strong covalent bonds, a lot of energy is needed to break them

melting points of p, s, cl, ar

p, s, cl are molecular substances, have low melting points due to weak van der walls forces. sulfur is higher than the others as it is a larger molecule. ar has a very low melting point ad it exists as an individual atom, meaning very weak van der walls forces

first ionisation energy generally _____

increases

why does first ionisation increase?

number of protons increases, stronger attraction between nucleus and electrons, harder to remove electrons