Answer:
It decreases
Explanation:
As one moves from left to right on the periodic table, the radius of atoms reduces due to the nuclear pull.
- The size of an atom estimated by the atomic radius is taken as half of the internuclear distance between the two covalently bonded atoms of non-metallic elements.
- Across a period, atomic radius decreases progressively from left to right.
- This is due to the increasing nuclear charge without attendant increase in the number of electronic shell.
<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:

That's because the first and last carbon atoms cannot be branched to form an isomer . Therefore only the three middle carbon atoms can form isomers.