Which order of relative size amongst the following is incorrec ?

Options

A. `LI lt Na lt K`
B. `O lt N lt F`
C. `AI lt Mg lt Na`
D. `F lt CI lt Br`

Answer

To determine which order of relative size among the given elements is incorrect, we need to understand the trends in atomic size within the periodic table. Here’s a step-by-step solution:

### Step 1: Identify the Elements
First, identify the elements mentioned in the question. For example, if the elements are Lithium (Li), Sodium (Na), Potassium (K), Nitrogen (N), Oxygen (O), and Fluorine (F), we need to analyze their positions in the periodic table.

### Step 2: Understand the Group Trend
In the periodic table, atomic size increases as you move down a group. This is because additional electron shells are added, which increases the distance between the nucleus and the outermost electrons. For example:
- Lithium (Li) is in Period 2.
- Sodium (Na) is in Period 3.
- Potassium (K) is in Period 4.

Thus, the order of size from smallest to largest among these three would be:
**Li < Na < K**

### Step 3: Understand the Period Trend
As we move from left to right across a period, atomic size decreases. This is due to the increase in nuclear charge (more protons) without a significant increase in electron shielding, which pulls the electrons closer to the nucleus. For example:
- Nitrogen (N), Oxygen (O), and Fluorine (F) are in Period 2.
- The order of size from largest to smallest would be:
**N > O > F**

### Step 4: Compare the Orders
Now, compare the orders derived from the group and period trends:
- For Group (Li, Na, K): **Li < Na < K** (Correct)
- For Period (N, O, F): **N > O > F** (Correct)

### Step 5: Identify the Incorrect Order
If the question provides a specific order that contradicts the trends established in Steps 2 and 3, that order is the incorrect one. For instance, if the order given is **F < O < N**, that would be incorrect because we know that **N > O > F**.

### Conclusion
Thus, the incorrect order of relative size among the given elements can be identified based on the periodic trends discussed.

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