Why is the ionisation enthalpy of hydrogen higher than that of sodium ?

Why is the ionisation enthalpy of magnesium higher than that of potassium ?

The first ionisation enthalpy of nitrogen is higher than that of oxygen but the second ionisation enthalpy is higher in oxygen than that of nitrogen. Explain

The first ionization enthalpy of magnesium is higher than that of sodium. On the other hand, the second ionization enthalpy of sodium is very much higher than that of magnesium. Explain.

The first ionization enthalpy of magnesium is higher than that of sodium. On the other hand, the second ionization enthalpy of sodium is very much higher than that of magnesium. Explain.

The first ionization enthalpy of magnesium is higher than that of sodium. Explain.

Give reasons: Why is first ionization enthalpy of Cu is higher than that of Na?