Coulomb repulsion between protons in the nucleus arises because protons are positively charged and like charges repel each other. If this repulsion were not countered, the nucleus would not be stable. This Coulomb repulsion is overcome by the **strong nuclear force**, which is a force that acts between nucleons (protons and neutrons) and is much stronger than the Coulomb force at short distances (on the order of 10−15 meters). The strong nuclear force is attractive, and it binds protons and neutrons together within the nucleus. At very short distances, the strong nuclear force is strong enough to overcome the repulsive Coulomb force between protons, ensuring the stability of the nucleus. This is why nuclei, despite the Coulomb repulsion between protons, can remain stable.
An electron in the hydrogen atom initially in the fourth excited state makes a transition to \( n^{th} \) energy state by emitting a photon of energy 2.86 eV. The integer value of n will be 1cm.
Considering the Bohr model of hydrogen like atoms, the ratio of the radius $5^{\text {th }}$ orbit of the electron in $\mathrm{Li}^{2+}$ and $\mathrm{He}^{+}$is
