Explain how shielding contributes to the atomic radius trend within a group.
Shielding refers to the effect of inner electron shells on the outer electron shell in an atom. It occurs when the negatively charged electrons in inner shells repel the negatively charged electrons in the outermost shell. This repulsion reduces the attractive force between the positively charged nucleus and the outer electrons.
The atomic radius trend within a group generally increases from top to bottom. This trend can be explained by the concept of shielding. As we move down a group, each subsequent element has an additional electron shell compared to the previous one. These additional shells act as a shield or barrier between the outermost electrons and the positively charged nucleus. The inner electron shells shield the outer electrons from the full nuclear charge, reducing their effective attraction towards the nucleus.
As a result, the outermost electrons experience less net attraction to the nucleus, making the atom larger. The increase in atomic radius down a group can be attributed to the increased number of electron shells contributing to the shielding effect.
To determine how shielding contributes to the atomic radius trend within a group, you can follow these steps:
1. Identify the group number of the elements you are comparing.
2. Determine the number of electron shells for each element in the group. This can be found by referring to the periodic table and noting the period or row number of each element.
3. Compare the number of electron shells between the elements in the group, starting from the top and moving down.
4. Observe how the addition of electron shells affects the shielding effect on the outermost electrons.
5. Note how the shielding effect decreases the net attraction between the outer electrons and the nucleus, resulting in an increase in atomic radius within the group.
By understanding the concept of shielding and considering the number of electron shells in each element of a group, you can explain how shielding contributes to the atomic radius trend.