How many electrons are in the 2nd principle energy level (n = 2) of aphosphorus atom?

To determine how many electrons are in the second principle energy level (n = 2) of a phosphorus atom, we need to look at the electron configuration of phosphorus.

1. Understanding Phosphorus: Phosphorus has an atomic number of 15, meaning it has 15 electrons when neutral.

2. Electron Configuration: The electron configuration of phosphorus is as follows:

   • 1s² (2 electrons)
   • 2s² (2 electrons)
   • 2p⁶ (6 electrons)
   • 3s² (2 electrons)
   • 3p³ (3 electrons)

3. Counting Electrons in n = 2: The second principle energy level (n = 2) includes:

   • 2s² (2 electrons)
   • 2p⁶ (6 electrons)

4. Total in n = 2: So, the total number of electrons in the second principle energy level is: $2 + 6 = 8 \text{ electrons}$

Final Answer

There are 8 electrons in the 2nd principle energy level (n = 2) of a phosphorus atom.