Arrange the following atoms and/or ions in the order of increasing size:Br ^–, Kr, Rb⁺, Sr²⁺.

• A. Kr < Br^- < Sr²⁺ < Rb⁺
• B. Kr < Sr²⁺ < Rb⁺ < Br^-
• C. Sr²⁺ < Rb⁺ < Kr < Br^-
• D. Rb⁺ < Sr²⁺ < Kr < Br^-
• E. Br^- < Kr < Rb⁺ < Sr²⁺

Answer: (C)

Verified step by step guidance

1. Step 1: Understand the concept of atomic and ionic size. Atomic size generally increases down a group and decreases across a period. For ions, cations (positively charged) are smaller than their neutral atoms, while anions (negatively charged) are larger.
2. Step 2: Identify the position of each element or ion in the periodic table. Bromine (Br) is in Group 17, Krypton (Kr) is in Group 18, Rubidium (Rb) is in Group 1, and Strontium (Sr) is in Group 2.
3. Step 3: Consider the charge of each ion. Br- is an anion, Rb+ is a cation, and Sr2+ is a cation. Krypton (Kr) is a neutral atom.
4. Step 4: Compare the sizes based on their charges and positions in the periodic table. Cations are smaller than their neutral atoms, and anions are larger. Therefore, Rb+ and Sr2+ will be smaller than Kr, and Br- will be larger.
5. Step 5: Arrange the atoms and ions in order of increasing size: Sr2+ < Rb+ < Kr < Br-.