The electron configuration of carbon atom in its excited state is

Analyze the question: You need the excited-state electron configuration of carbon (atomic number 6, so 6 electrons).

Concept:

• Ground state: electrons fill the lowest energy orbitals first (Aufbau principle), and Hund's rule applies to the p orbitals. Carbon ground state: 1s² 2s² 2px¹ 2py¹ (2pz⁰)
• Excited state: an electron is promoted to a higher-energy orbital, but the total number of electrons stays at 6. For carbon, one 2s electron moves into the empty 2pz orbital. This gives four unpaired electrons, which is why carbon forms four bonds (as in CH₄).

Check each option:

• A. 1s² 2s² 2px² 2py⁰ has 6 electrons, but it is just a different arrangement with paired electrons in 2px. It breaks Hund's rule, so it is a higher-energy, unusual state and not the standard excited state for bonding.
• B. 1s² 2s² 2px¹ 2py¹ is the ground state of carbon, with 6 electrons.
• C. 1s² 2s¹ 2px¹ 2py¹ 2pz¹ has 2 + 1 + 3 = 6 electrons. One 2s electron has been promoted to 2pz, giving four unpaired electrons. This is the classic excited state.
• D. 1s¹ 2s² 2px¹ 2py¹ has 1 + 2 + 2 = 5 electrons, so it is wrong for carbon.

Tip: For carbon's excited state, remember "2s¹ 2p³". Promoting one electron from 2s to 2p gives four unpaired electrons, which explains carbon's tetravalency and sp³ hybridisation. Always count the electrons first, since this quickly eliminates options like D.