Question

Rank elements Li, Be, B, C in increasing first ionization energy:

• A. Li<B<C<Be
• B. Li<C<B<Be
• C. Be<C<B<Li
• D. Li<Be<B<C

Hint:

The first ionization energy generally increases across a period from left to right.

Answer 1

The Correct Option is D

Step 1: Understanding ionization energies.
Ionization energy increases across a period and decreases down a group. However, there are exceptions due to electron configurations, especially in p-block elements.
Step 2: Explanation of the order.
- Li (Lithium) has the lowest first ionization energy because it is an alkali metal with a single electron in its outermost shell. - Be (Beryllium) has a higher ionization energy than Li because it has a stable \( 2s^2 \) configuration.
- B (Boron) has a lower ionization energy than C because it has one electron in the \( 2p \) orbital, which is easier to remove than a fully filled \( 2s^2 \) orbital in carbon.
- C (Carbon) has the highest first ionization energy because it has a half-filled \( 2p^2 \) orbital, which is relatively stable.
Step 3: Conclusion.
Thus, the correct order of increasing first ionization energy is: \[ \text{Li}<\text{Be}<\text{B}<\text{C} \] which corresponds to option (D).

Answer 2

Step 1: Lithium (Li) has the lowest first ionization energy — it easily loses its single outer electron.

Step 2: Beryllium (Be) is higher than Li because of its extra-stable filled 2s² setup.

Step 3: Boron (B) is actually lower than Carbon because its lone 2p electron is easier to remove than a 2s² electron, while Carbon's 2p² setup gives it extra stability.

Step 4: So the increasing order is Li < Be < B < C — option (D).

Answer 3

Elimination approach: Reversing the whole trend, so that the values fall instead of rise across the period, is wrong because ionization energy generally increases left to right across period 2. The remaining wrong options scramble beryllium's position relative to boron and carbon in a way that doesn't fit a simple, steady, left-to-right rise. Applying the straightforward period trend consistently across lithium, beryllium, boron, and carbon in that order gives an increasing sequence, option (D).