Elements of I A group give colour in Bunsen burner due to

Options

A. Low heat of sublimation
B. Low melting point
C. Softness
D. 1 electron in outermost shell

Answer

### Step-by-Step Solution

1. **Identify the Group**: The question refers to the elements of Group 1A in the periodic table, which are known as alkali metals. These include Lithium (Li), Sodium (Na), Potassium (K), Rubidium (Rb), Cesium (Cs), and Francium (Fr).

2. **Properties of Alkali Metals**: Alkali metals are characterized by being very soft, shiny, having low melting points, and being highly reactive. They tarnish quickly when exposed to air.

3. **Understanding Flame Test**: When alkali metals are heated in a flame, they exhibit characteristic colors. This phenomenon is known as the flame test.

4. **Ionization Energy**: The key to understanding why alkali metals give color in a flame lies in their low ionization energy. Ionization energy is the energy required to remove an electron from an atom.

5. **Electron Excitation**: Alkali metals have one electron in their outermost shell (NS1 configuration). When these metals are heated, this outer electron gets excited to a higher energy level.

6. **Energy Emission**: As the excited electron returns to its ground state, it releases energy in the form of light. This emitted light corresponds to specific wavelengths, which are perceived as colors.

7. **Conclusion**: The characteristic colors observed during the flame test of alkali metals are due to the presence of one electron in the outermost shell, which leads to low ionization energy and subsequent electron excitation and energy emission.

8. **Correct Answer**: The correct answer to the question is that alkali metals give color in a Bunsen burner due to having one electron in their outermost shell, which results in low ionization energy.