The nuclei of atoms become unstable when the repelling forces of the protons cannot be balanced by the number of neutrons in the nucleus. It then re-arranges itself randomly to a more stable configuration by emitting any of a series of particles. During radioactive decay, an atom does not collapse.
Since an atom is mostly empty space - that is it’s nucleus is relatively distant from the electron shells so, in the presence of extreme forces such as gravity inthe collapse of a large star, the inward pressures on the atom overcome the natural balance of the atomic structure and the ‘empty space’ disappears as nuclei are mashed together by the intense pressures and a neutron star is formed. Under even more external pressure, even the neutron star can collapse to form a black hole.
<u>Answer:</u>
<u>For A:</u> The equation is 
<u>For B:</u> The equation is 
<u>For C:</u> The equation is 
<u>Explanation:</u>
Alpha decay process is the process in which nucleus of an atom disintegrates into two particles. The first one which is the alpha particle consists of two protons and two neutrons. This is also known as helium nucleus. The second particle is the daughter nuclei which is the original nucleus minus the alpha particle released.

Beta decay process is defined as the process the neutrons get converted into an electron and a proton. The released electron is known as the beta particle. In this process, the atomic number of the daughter nuclei gets increased by a factor of 1 but the mass number remains the same.

<u>For A:</u> Uranium-238 emits an alpha particle
The nuclear equation for this process follows:

<u>For B:</u> Plutonium-239 emits an alpha particle
The nuclear equation for this process follows:

<u>For C:</u> Thorium-239 emits a beta particle
The nuclear equation for this process follows:

(1)
At phase A, the water is fully solid, At phase C the water is fully liquid and at phase E the water is fully gas. At this ponts all the substance is in one state other than the fact that its molecules are getting more excited as they gain more energy. This is why there is an increase in temperatures. At the transition points water is changing phase and therefore at any point in between the transition not all water will be in the same phase.
(2)
Point F
This is because the solid water stops rising in temperatures and begins changing phase into liquid water. This is the highest temperatures that the solid water can attain without turning into liquid. You can see from the graph that the temperatures rise at this point levels off between point F and G
(3)
Point H
This is because the liquid water stops rising in temperatures and begins changing phase into gaseous form. This is the highest temperatures that the liquid water can attain without turning into gas/water vapor. You can see from the graph that the temperatures rise at this point levels off between point H and I.
(4)
The energy is increasing
You can see from the graph that energy is being absorbed by the water (due to increases in energy on the x-axis on the graph) but there is no corresponding rise in temperatures in y-axis. This means the energy begin absorbed is being used to change the phase of the water.
(5)
The water is changing phases
Because the energy absorbed is being used to change the phase of the liquid. The energy is being used to break the bonds between the molecules so the molecules become farther apart and causing a change in phase on the water. Therefore the vibrational moments of the molecules (responsible for rising in temperatures) remain the same over this latent phase. This energy absorbed to change phase is called latent energy/heat.
Learn More:
For more on change of phase of water check out;
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I would say that you should wear a lab coat, safety goggles, and gloves
when the teacher says so - not everything in a lab is dangerous, so
there is no need to always wear these. But when the teacher says you
should - then you should.