Find the odd one out.
Sodium, Calcium, Iron, Oxygen

The correct option is Oxygen.

Step-by-Step Explanation:

1. Classify the given elements based on their physical and chemical properties:

• Sodium (Na): A metallic element (alkali metal).

• Calcium (Ca): A metallic element (alkaline earth metal).

• Iron (Fe): A metallic element (transition metal).

• Oxygen (O): A non-metallic element (gas at room temperature).

2. Identify the common pattern and the odd one out:

Sodium, Calcium, and Iron are all classified as metals and are solid at room temperature under standard conditions. On the other hand, Oxygen is a non-metal and exists as a gas at room temperature.

Therefore, Oxygen is the odd one out among the given options.