Mention five elements of period 3!
Na, Mg, Al, Si, P, S, Cl, Ar
Why does atomic radius decrease across period 3?
Greater attractive force due to increasing positive nuclear charge, which pulls valence electrons closer to the nucleus.
How does the ionic radius of positively charged ions compared to its atom?
Ionic radius are much smaller
Between Mg2+ and S2-, which one has larger ionic radius?
S2-
Among elements in period 3, which one has the highest melting point?
Silicon
Why does chlorine have a very small melting point?
It has a simple molecule with strong covalent bond but weak van der Waals' forces
Among all elements in period 3, which one is the best conductor?
Aluminium
How does the trend of first ionisation energy across period 3?
Increases
What happens when sodium reacts with oxygen?
Burns vigorously with yellow flame
Mention three elements of period 3 which can react with water!
Na, Mg, Cl
Arrange these three elements from the most reactive one with chlorine: Si, Al, P
Al, Si, P
What is the oxidation number of sulfur in sulfur dioxide?
+4
Mention two elements of period 3 which the oxides do not react with water!
Na, Mg
What happens when the oxide of phosphor reacts with water?
Reacts vigorously and dissolves in water
Which oxide of period 3 element is amphoteric?
Aluminium oxide
How does magnesium oxide and magnesium hydroxide work in our stomach?
They neutralise excess acid
