Question

Which of the following is an alkali metal?

• A. Barium
• B. Rubidium
• C. Strontium
• D. Gallium

Hint:

Use a simple mnemonic to remember the Group 1 elements instantly: "LiNaK Rubs Cesium's Fridge" (Li, Na, K, Rb, Cs, Fr). This helps ensure you never mix up Group 1 and Group 2 metals during an exam!

Answer 1

The Correct Option is B

Step 1: Understanding the Question:
We need to identify which of the given chemical elements belongs to the alkali metal family in the periodic table.

Step 2: Key Formula or Approach:
Alkali metals are the chemical elements residing in Group 1 (IA) of the modern periodic table (excluding Hydrogen). They possess a single valence electron in their outermost shell ($n\text{s}^1$). The complete group consists of Lithium (Li), Sodium (Na), Potassium (K), Rubidium (Rb), Cesium (Cs), and Francium (Fr).

Step 3: Detailed Explanation:
Let's check the group classification for each option provided:
(A) Barium (Ba): Belongs to Group 2, making it an Alkaline Earth Metal.
(B) Rubidium (Rb): Belongs to Group 1, right below Potassium. This classifies it squarely as an Alkali Metal.
(C) Strontium (Sr): Belongs to Group 2, making it an Alkaline Earth Metal.
(D) Gallium (Ga): Belongs to Group 13, making it a post-transition metal.
Therefore, Rubidium is the correct selection.

Step 4: Final Answer:
Rubidium is an alkali metal, which corresponds to option (B).