Classification of Elements and Periodicity in Properties

The correct statement(s) regarding the periodic properties of elements is(are)

1. Second ionization enthalpy of carbon atom is less than that of boron atom.
2. Increasing order of ionic radii: Al3+<Mg2+<Na+
3. Under identical conditions, in solid state, the density of potassium metal is more than density of sodium metal.
4. The H–H bond is weaker than F–F bond.