The atomic number of sodium is 11, fluorine is 9 and neon is 10. Why are sodium and fluorine very reactive while neon shows almost no reactivity.

Why is fluorine a very reactive halogen ?

Explain why sodium is less reactive than potassium ?

Sodium and aluminium have atomic numbers of 11 and 13 respectively they are separated by one element in the periodic table and have valencies of 1 and 3 respectively. chlorine and potassium are also separated by one element in the periodic table(their atomic numbers are 17 and 19 respectively) and yet both have valency of one. explain your answer

Mark' T' if the statement is true and 'F' if the statement is false. Sodium is very reactive metal. ( )

Estimate the average mass density of a sodium atom assuming its size to be about 2.5 overset@A . (Use the known values of Avogadro’s number and the atomic mass of sodium). Compare it with the density of sodium in its crystalline phase : 970 kg m^-3 . Are the two densities of the same order of magnitude ? If so, why ?