Shielding Changes and The Periodic Table
Shielding is how inner electrons influence the force of attraction between the nucleus and the outer shell electrons. Atoms with few energy levels shielding is less than those with many energy levels.
Now shielding influences three main things, atomic radii, ionic radii, and electronegativity. Those are the three things that shielding influences.
If you think about the periodic table as a big rectangle, even though it’s not a perfect rectangle, as you go to the right of the periodic table, which we have rows which we could also call periods, so as you go to the right of a period shielding stays constant.
For shielding to stay constant that must mean that something else is staying constant or not changing. The reason that shielding stays constant is because the number of energy levels is the same. As you move to the right of the period the number of energy levels is the same.
That doesn’t change as you move down the period because every element in a period has the same amount of energy levels. As you go down periodic table shielding increases. Here it stays constant, but as you move down what we’d call a column, or we can also call it a group, as you move down a group shielding increases.
The shielding increases as the number of energy levels increases. Remember, it didn’t increase here because energy levels were staying the same, but now that energy level increases the shielding increases as well.
There is going to be more shielding in a caesium atom than in a lithium atom because a caesium atom is lower down than a lithium atom. Overall, shielding increases as you move to the lower right corner.
If you have an element over here the shielding is going to be a lot higher than an element over here. Now just by remembering this one fact that shielding increases as you move down a group can help you determine by just looking at where an element is situated geographically on the periodic table, you can just look at it now, and get an idea of how much it shields.
Just remember that shielding is how inner electrons influence the force of attraction between the nucleus and the outer shell electrons.