Question

1. krypton (kr)
2. zinc (zn)
3. oxygen (o)

Explanation:

Step1: Recall electron - filling rules

Electrons fill orbitals in order of increasing energy (1s < 2s < 2p < 3s < 3p < 4s < 3d < 4p etc.), with 1s holding 2 electrons, 2s holding 2 electrons, 2p holding 6 electrons, 3s holding 2 electrons, 3p holding 6 electrons, 4s holding 2 electrons, and 3d holding 10 electrons.

Step2: Determine electron configuration of Krypton (Kr, atomic number = 36)

Electrons fill as follows: 1s²2s²2p⁶3s²3p⁶4s²3d¹⁰4p⁶.

Step3: Write noble - gas configuration of Krypton

The noble gas before Kr is Argon (Ar, atomic number = 18). So the noble - gas configuration is [Ar]4s²3d¹⁰4p⁶.

Step4: Determine electron configuration of Zinc (Zn, atomic number = 30)

Electrons fill as 1s²2s²2p⁶3s²3p⁶4s²3d¹⁰.

Step5: Write noble - gas configuration of Zinc

The noble gas before Zn is Argon (Ar). So the noble - gas configuration is [Ar]4s²3d¹⁰.

Step6: Determine electron configuration of Oxygen (O, atomic number = 8)

Electrons fill as 1s²2s²2p⁴.

Step7: Write noble - gas configuration of Oxygen

The noble gas before O is Helium (He). So the noble - gas configuration is [He]2s²2p⁴.

Answer:

1. Electron Configuration: 1s²2s²2p⁶3s²3p⁶4s²3d¹⁰4p⁶

Noble Gas Configuration: [Ar]4s²3d¹⁰4p⁶

1. Electron Configuration: 1s²2s²2p⁶3s²3p⁶4s²3d¹⁰

Noble Gas Configuration: [Ar]4s²3d¹⁰

1. Electron Configuration: 1s²2s²2p⁴

Noble Gas Configuration: [He]2s²2p⁴