Are the followinf true:
atomic radii decreases from left to right, across a row
atomic radii increases from top to bottom of a column
correct on both.
Thanks :)
Yes, both statements are true.
To understand why, let's start with the first statement: "Atomic radii decreases from left to right, across a row."
As you move from left to right across a row in the periodic table, you are increasing the number of protons in the nucleus of the atoms. The increased positive charge of the nucleus pulls the electrons closer to the center, reducing the size of the atom. This decrease in atomic size is due to a greater number of protons exerting a stronger pull on the electrons, resulting in a smaller atomic radius.
Now, let's move on to the second statement: "Atomic radii increases from top to bottom of a column."
When you move down a column in the periodic table, you are adding new energy levels (shells) to the atoms. Each new energy level further increases the distance between the nucleus and the outermost electrons. These additional energy levels shield the outermost electrons from the attractive force of the nucleus, reducing the effective nuclear charge experienced by the valence electrons. As a result, the outermost electrons are less strongly attracted to the nucleus, causing the atomic radius to increase as you move down a group or column.
In summary, the atomic radius decreases from left to right across a row due to an increase in the effective nuclear charge, while the atomic radius increases from top to bottom of a column due to the addition of new energy levels.