What trends the atomic radii of group 2A ?what trends the atomic radii of period 3? Why this trend occurs?
Ans
Atomic radii of group 2A increases . Atomic radii of period 3 decreases .
I don't know how to answer the last question!! Please help me !
To understand why the atomic radii trend in Group 2A (alkaline earth metals) and Period 3 occurs, we need to consider their electron configuration and the factors affecting atomic size.
In Group 2A, the atomic radii increase as you move down the group. This is because each subsequent element adds an additional energy level (shell) of electrons. The increase in energy levels leads to an increase in atomic size because more electrons are being added to the outermost shell, resulting in increased electron-electron repulsion. This causes the outermost shell to be farther away from the nucleus, increasing the atomic radius.
In Period 3, the atomic radii generally decrease as you move across from left to right (excluding the noble gases). This trend can be explained by two main factors: effective nuclear charge and electron shielding.
Effective nuclear charge refers to the positive charge experienced by the valence electrons from the nucleus. As you move across Period 3, the number of protons in the nucleus increases, resulting in a greater effective nuclear charge. The increased positive charge pulls the electrons closer to the nucleus, reducing the atomic radius.
Electron shielding also plays a role in the trend. Shielding refers to the repulsion between electrons in different energy levels. As you move across Period 3, the number of inner (core) electrons remains constant while the number of valence electrons increases. The increased electron-electron repulsion leads to a slight expansion of electron clouds and offsets the effect of increasing nuclear charge. However, this shielding effect is not sufficient to completely counterbalance the increase in nuclear charge, resulting in a net decrease in atomic radii.
In summary, the atomic radii of Group 2A increase down the group due to the addition of energy levels, while the atomic radii of Period 3 generally decrease across the period due to the combined effects of increasing effective nuclear charge and limited electron shielding.