Answer:
The atomic radius is a measure of the size of an atom. It represents the distance from the nucleus to the outermost electron shell or energy level. The relative size of an atom's electron cloud is determined by its atomic radius.
The electron cloud refers to the region around the nucleus where electrons are most likely to be found. According to the quantum mechanical model of the atom, electrons exist in specific energy levels or shells, and each shell can hold a certain number of electrons. The first shell, closest to the nucleus, can hold up to 2 electrons, while the second shell can hold up to 8 electrons, and so on.
The atomic radius increases as you move down a group or column in the periodic table. This is because each subsequent energy level is further from the nucleus, resulting in a larger electron cloud. For example, in Group 1 (the alkali metals), lithium has a smaller atomic radius than sodium, which has a smaller atomic radius than potassium.
On the other hand, as you move across a period from left to right in the periodic table, the atomic radius generally decreases. This is due to an increase in effective nuclear charge, which is the attraction between the positively charged protons in the nucleus and the negatively charged electrons. As more protons are added to the nucleus, they pull the electrons closer, resulting in a smaller atomic radius. For example, fluorine has a smaller atomic radius than oxygen, which has a smaller atomic radius than nitrogen.
It is important to note that there are exceptions to this general trend. For example, noble gases have larger atomic radii than would be expected based on their position in the periodic table. This is because their outermost electron shells are completely filled with electrons, resulting in increased repulsion between these electrons and a larger overall size.
In summary, the relative size of an atom's electron cloud is determined by its atomic radius. The atomic radius increases as you move down a group in the periodic table and generally decreases as you move across a period from left to right.
Step-by-step explanation: