Question

determine which of the following electron configurations are not valid: 26) 1s²2s²2p⁶3s²3p⁶4s²4d¹⁰4p⁵ 27) 1s²2s²2p⁶3s³3d⁵ 28) ra 7s²5f⁶ 29) kr 5s²4d¹⁰5p⁵ 30) xe

Explanation:

Step1: Recall electron - filling order

Electrons fill orbitals in the order 1s, 2s, 2p, 3s, 3p, 4s, 3d, 4p, 5s, 4d, 5p, etc.

Step2: Analyze 26)

The configuration 1s²2s²2p⁶3s²3p⁶4s²4d¹⁰4p⁵ is incorrect because after filling 4s², the next orbitals to fill are 3d, not 4d.

Step3: Analyze 27)

The configuration 1s²2s²2p⁶3s³3d⁵ is incorrect. The s - orbital can hold a maximum of 2 electrons, so 3s³ is not valid.

Step4: Analyze 28)

The configuration [Ra]7s²5f⁶ is a valid electron - configuration as it follows the filling order. Radium (Ra) has a noble - gas core, and then electrons fill 7s and 5f orbitals as expected.

Step5: Analyze 29)

The configuration [Kr]5s²4d¹⁰5p⁵ is a valid electron - configuration following the filling order for elements in the fifth period after the krypton core.

Step6: Analyze 30)

The configuration [Xe] represents the electron - configuration of xenon and is valid as it is the ground - state electron - configuration of the noble gas xenon.

Answer:

1. Not valid
2. Not valid
3. Valid
4. Valid
5. Valid