Which of the following statements is wrong?

1. The uncertainty principle is $∆x·∆p\ge \frac{h}{4\mathrm{\pi }}$

2. Half-filled and fully filled orbitals have greater stability due to greater exchange energy,

greater symmetry, and a more balanced arrangement.

3. The energy of the 2s orbital is less than the energy of the 2p orbital in the case of hydrogen-like atoms.

4. De-Broglie's wavelength is given by $\lambda =\frac{h}{mv}$, where m= mass of the particle, v = group velocity of the particle.