Because as you go down the group the atomic number increase. And by that the number of electrons in the electron cloud increases, thus widening the atomic radii.
***************2nd Opinion****************
If that were true, then atomic radius would also increase as you move to the right in a series.
The reason atomic radius increases going down a family is that each atom has electrons in a whole new energy level compared to the atom above it. For example, Group 1: The outer shells are 1s, 2s, 3s, 4s, 5s, 6s, 7s.
1. Generally (groups 1,2, 4, 5, 12, 13, 14, 15, 16, 17, 18) the atomic radius increase with the increase of the atomic number (down). 2. For the other groups the variation is irregular; see the table at the link below.
the atomic radius increases down a family simply because there are more electrons present and more shells.
as you go down a period/family the atomic radii increases
Increases down a group as the energy level (shells) increases.
Generally the atomic radius of elements increase down in the group.
Generally (groups 1,2, 4, 5, 12, 13, 14, 15, 16, 17, 18) the atomic radius increase with the increase of the atomic number (down).
The Atomic Radius does the same.
decreases
Atomic radius
Decreases. Look at the images under atomic radius, on wikipedia.
The size of an atom refers to its atomic radius. Atomic radius generally increases down a group. This is because the number of energy levels increase down a group with each additional period. Each of the subsequent energy levels are larger than the last, increasing the distance of the electrons from the nucleus, which increases the atomic radius.Atomic radius generally decreases across a period. This is because electrons are being added to the same energy level at the same time that protons are being added to the nucleus. This creates a stronger force of attraction by the nucleus for the electrons, which pulls the electrons closer to the nucleus, decreasing the atomic radius.It is important to note that the periodic trends are not laws. There are exceptions to the general trends in both the representative elements and the transitional elements.
An increase in atomic number would be accompanied by a decrease in radius, and an increase in electronegativity.
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Atomic radius
The atomic radius generally increases as you move down a column in the periodic table. This is because each successive element has an additional energy level, leading to larger orbits for the electrons and an overall increase in atomic size.
The atomic radius increases from top to bottom within a group.
Going down and to the left on the periodic table, atomic radius increases. Therefore, the smallest atomic radius is that of Helium (He), and the largest is that of Francium (Fr). Coincidentally, these are also the most and least reactive elements.
Decreases. Look at the images under atomic radius, on wikipedia.
The number of energy levels increase within a group. Therefor the atomic radius increases. So the atomic volume also increases.The atomic radius also increases in a group.For metals, reactivity increases down the group. For non-metals, reactivity decreases down a group.
The atomic radius decreases across a period from left to right and increases down in a given group. That means that since the lower the element is in a group, the larger the atomic radius will be. The atoms with the largest atomic radii are located in Group I and are at the bottom of groups.
The size of an atom refers to its atomic radius. Atomic radius generally increases down a group. This is because the number of energy levels increase down a group with each additional period. Each of the subsequent energy levels are larger than the last, increasing the distance of the electrons from the nucleus, which increases the atomic radius.Atomic radius generally decreases across a period. This is because electrons are being added to the same energy level at the same time that protons are being added to the nucleus. This creates a stronger force of attraction by the nucleus for the electrons, which pulls the electrons closer to the nucleus, decreasing the atomic radius.It is important to note that the periodic trends are not laws. There are exceptions to the general trends in both the representative elements and the transitional elements.
An increase in atomic number would be accompanied by a decrease in radius, and an increase in electronegativity.
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A free proton is the nucleus of hydrogen atom and free alpha particle is the nucleus of helium atom and they may exist out side the atomic radius.
Atomic radius increases down the group. It decreases along a period.