Arrange the events involved in nuclear fusion in the correct order.

1. The colliding nuclei fuse to form larger helium atoms having two protons and two neutrons.

2. Bare nuclei collide with each other due to massive amounts of heat.

3. The pressure of hydrogen gas increases, and the gas reaches extreme temperatures.

4. Hydrogen atoms shed their electrons.

The correct order is 3 4 2 1. At the high temperatures like in the sun, hydrogen gas reaches extreme temperatures which causes hydrogen to shed their electrons. Due to massive amounts of heat, the protons are moving so fast that the electrical repulsion cannot prevent them from colliding and fusing together to form helium atoms.

In a nuclear fusion, we need the nuclei to move around very quickly in order to overcome the energy of repulsion. The first step to this is acquiring the temperature. Due to the pressure of the hydrogen gas, this is achieved by the ideal gas equation PV=nRT. After that, it is the atoms shed their electrons that are a barrier to collisions since they repel each other. Then, the remaining bare nuclei collide with each other freely and a small fraction of them form a new nucleus. The nuclei formed from hydrogen are helium ones; they contain 2 protons and 2 neutrons and they are also called a-particles. They are a radioactive product.

To recap, the correct order is:

3, 4, 2, 1 (first to last)