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: Define alkali metals.
Alkali metals are the Group 1 elements (excluding hydrogen): Li, Na, K, Rb, Cs, Fr. They have one valence electron, $ns^1$. So we just check which option lies in Group 1.
Step 2: Place Barium.
Barium (Ba) is in Group 2, so it is an alkaline earth metal, not alkali.
Step 3: Place Rubidium.
Rubidium (Rb) sits directly below potassium in Group 1, so it is an alkali metal.
Step 4: Place Strontium.
Strontium (Sr) is in Group 2, an alkaline earth metal.
Step 5: Place Gallium.
Gallium (Ga) is in Group 13, a post-transition metal.
Step 6: Select the Group 1 element.
Only Rubidium belongs to Group 1, so it is the alkali metal - option (2).
\[ \boxed{\text{Alkali metal: Rubidium (option 2)}} \]