Rank the following atoms and ions from smallest to largest radius:
Ba,Ba^2+,Cs,Sr^2+
In order to rank the atoms and ions from smallest to largest radius, we need to consider their electronic configurations and the effects of atomic number and charge on the atomic radius.
1. Start by comparing the neutral atoms, Ba and Cs.
- Ba has an atomic number of 56 and its electronic configuration is [Xe] 6s². Its outermost electron is in the 6s orbital.
- Cs has an atomic number of 55 and its electronic configuration is [Xe] 6s² 5d¹ 4f¹³. Its outermost electron is in the 6s orbital as well.
Since both atoms have the same valence electron configuration (6s²) and Ba has a higher atomic number, Ba has a smaller atomic radius than Cs.
2. Now, let's compare the cations, Ba²⁺ and Sr²⁺.
- Ba²⁺ is a cation formed by losing two electrons from the neutral Ba.
- Sr²⁺ is a cation formed by losing two electrons from the neutral Sr.
Since both cations have the same electronic configuration as their neutral counterparts but with two fewer electrons, they will have a smaller atomic radius than their respective neutral atoms. However, since Sr has a higher atomic number than Ba, Sr²⁺ will have a larger atomic radius than Ba²⁺.
Therefore, the ranked atoms and ions from smallest to largest radius are: Ba²⁺ < Ba < Cs < Sr²⁺.