Protons and neutrons are made up of smaller subatomic particles. When protons or neutrons get close enough to each other, they exchange particles (mesons), binding them together. Although the strong force overcomes electrostatic repulsion, protons do repel each other.

Also, neutrons and protons are made up of tinier particles called quarks. And it is the quarks that exchange force carrying particles between each other to give rise to the strong force. The strong force also attracts protons to protons or neutrons to neutrons.

A neutron is attracted to a proton and it is this force that holds a nucleus together. If this product is positive then the force is a repulsion and if it is negative the force is an attraction. Likewise the potential energy for the two particles is proportional to the product of the nucleonic charges.

Inside the nucleus, the attractive strong nuclear force between protons outweighs the repulsive electromagnetic force and keeps the nucleus stable. Outside the nucleus, the electromagnetic force is stronger and protons repel each other.

strong nuclear force

It’s pretty difficult and tedious because protons are very small and hard to see, as well as to differentiate from the neutrons. It takes a steady hand and a special set of forceps to perform this procedure.

The law of electrostatics says that like charges repel. So, if a nucleus contains two or more positively charged protons, they should repel each other. But in that case, why doesn‟t the nucleus fly apart? The answer to this question involves the four fundamental forces of nature.

In this case, 2 electrons from each atom are shared. This is called a double bond. When two oxygen atoms get close to each other, the attractions from the nucleus of both atoms attract the outer electrons. In this case, two electrons from each atom are shared.

The 2s orbital in calcium is more stable (more negative energy) than the 2p orbital even though the 2p orbital has its maximum electron density closer to the nucleus. The reason for this higher stability is: e.

The shielding effect explains why valence-shell electrons are more easily removed from the atom. The effect also explains atomic size. The more shielding, the further the valence shell can spread out and the bigger atoms will be. The effective nuclear charge is the net positive charge experienced by valence electrons.

s orbital

Across a period, effective nuclear charge increases as electron shielding remains constant. A higher effective nuclear charge causes greater attractions to the electrons, pulling the electron cloud closer to the nucleus which results in a smaller atomic radius.