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 there is a trend in atomic radii within Group 2A and Period 3, we need to consider the underlying principles of atomic structure and electron distribution.
In Group 2A (also known as Group 2 or the alkaline earth metals), the atomic radii increase as you move down the group. This is due to the increase in the number of electron shells or energy levels. As we move from beryllium (Be) to magnesium (Mg) to calcium (Ca) to strontium (Sr) to barium (Ba) to radium (Ra), each successive element has an additional energy level, resulting in larger atomic radii. This phenomenon occurs because each new energy level has a greater average distance of the electrons from the nucleus, leading to a larger atomic radius.
In Period 3, the atomic radii generally decrease from left to right. This is the case for elements sodium (Na), magnesium (Mg), aluminum (Al), silicon (Si), phosphorus (P), sulfur (S), chlorine (Cl), and argon (Ar). This trend can be attributed to two major factors: effective nuclear charge and electron shielding.
Effective nuclear charge refers to the net positive charge experienced by the outermost electrons. As we move from left to right across Period 3, the number of protons in the nucleus increases, resulting in a higher effective nuclear charge. The increased positive charge attracts the electrons closer to the nucleus, causing a decrease in atomic radius.
Electron shielding plays a role in atomic radii as well. The inner electron shells shield the outermost electrons from the full pull of the positive charge in the nucleus. However, in Period 3, the number of inner electrons remains constant at two. The increased positive charge from the growing number of protons is not effectively shielded by the same number of inner electrons, thereby pulling the outer electrons closer to the nucleus and decreasing atomic radii.
To summarize, in Group 2A, the atomic radii increase down the group due to the addition of new energy levels. In Period 3, the atomic radii generally decrease from left to right due to the increasing effective nuclear charge and insufficient electron shielding.