Assertion: Be and Mg do not impat characteristic colour to the flame.
Reason: both Be and Mg have high ionization energy.

Options

A. If both assertion and reason are true and reason is the correct explanation of assertion
B. If both assertion and reason are true but reason is not the correct explanation of assertion
C. If assertion is true but reason is false.
D. If both assertion and reason are false.

Answer

To analyze the assertion and reason provided in the question, we will break down the concepts step by step.

### Step 1: Understanding the Assertion
The assertion states that "Be and Mg do not impart characteristic colour to the flame." This means that when beryllium (Be) and magnesium (Mg) are heated in a flame, they do not produce a visible color that is typically associated with other metal ions.

### Step 2: Understanding the Reason
The reason given is "both Be and Mg have high ionization energy." Ionization energy is the energy required to remove an electron from an atom in its gaseous state. High ionization energy indicates that it is difficult to remove an electron from the outermost shell of an atom.

### Step 3: Analyzing the Relationship
Beryllium and magnesium are both alkaline earth metals. They have relatively high ionization energies compared to other metals in the same group. This high ionization energy means that it is difficult for these metals to lose electrons and get excited to higher energy levels when heated in a flame.

### Step 4: Electronic Configuration
- Beryllium (Be) has the electronic configuration of 1s² 2s².
- Magnesium (Mg) has the electronic configuration of 1s² 2s² 2p⁶ 3s².

Both elements have stable electronic configurations, with filled outer shells, making it energetically unfavorable for them to lose electrons.

### Step 5: Conclusion
Since Be and Mg do not easily lose electrons due to their high ionization energies, they do not get excited to higher energy levels when heated. As a result, they do not emit light in the visible spectrum, which is necessary to impart characteristic colors to the flame. Therefore, both the assertion and the reason are true, and the reason correctly explains the assertion.

### Final Answer
Both assertion and reason are true, and the reason correctly explains the assertion.

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