How many unpaired electron are in the p-orbitals of a fluorine atom?

1. Analyze the Question

The question asks for the number of unpaired electrons specifically in the p-orbitals of a neutral fluorine atom.

2. Explain the Concept

To find the number of unpaired electrons, we must follow these steps:

• Determine the Atomic Number: Fluorine (F) has an atomic number of 9. This means a neutral fluorine atom has 9 electrons.
• Write the Electronic Configuration: We distribute the 9 electrons into orbitals following the Aufbau principle (1s, 2s, 2p).
• Apply Hund’s Rule: Hund’s rule states that for degenerate orbitals (orbitals with the same energy, like the three p-orbitals), electrons fill them singly first before pairing up.

3. Show the Solution

• Step 1: Electronic Configuration The distribution of 9 electrons is: $1s^2 2s^2 2p^5$

• Step 2: Focus on the p-orbitals The $2p$ subshell can hold a maximum of 6 electrons across three orbitals ($p_x, p_y, p_z$). We have 5 electrons to place in these three orbitals.

• Step 3: Filling the orbitals (Hund's Rule) • Place 1 electron in $p_x$ • Place 1 electron in $p_y$ • Place 1 electron in $p_z$ • Now, go back and pair them: • Place 1 electron in $p_x$ (now paired) • Place 1 electron in $p_y$ (now paired) • The $p_z$ orbital remains with only 1 electron.

Visually, it looks like this: $( \uparrow \downarrow ) ( \uparrow \downarrow ) ( \uparrow )$ $p_x \quad p_y \quad p_z$

There is only 1 orbital that contains a single (unpaired) electron.

4. Identify the Answer

Comparing our result to the options provided, we see that there is 1 unpaired electron. This matches option C.

5. Exam Tip

Whenever you are asked for unpaired electrons in a p-block element, just look at the number of electrons in the p-orbital. If the number is 1, 2, or 3, that is the number of unpaired electrons. If the number is 4, 5, or 6, subtract that number from 6 to find the unpaired electrons (e.g., for $p^5$, $6 - 5 = 1$ unpaired electron).