1. (a) 2s, 2p, 3s, 3p, 4s, 3d, 4p, 5s, 4d, 5p, 6s, 4f, 5d, 6p, 7s, 5f, 6d, 7p
(b) 1s² 2s² 2p⁶ 3s² 3p⁶ 4s² 3d¹⁰ 4p⁶ 5s² 4d¹⁰ 5p⁶ 6s² 4f¹⁴ 5d¹⁰ 6p⁶ 7s² 5f¹⁴ 6d¹⁰ 7p⁶
(c) 1s² 2s² 2p⁶ 3s² 3p⁶ 4s² 3d¹⁰ 4p⁶ 5s² 4d¹⁰ 5p⁶ 6s² 4f¹⁴ 5d¹⁰ 6p⁶ 7s² 5f¹⁴ 6d¹⁰ 7p⁶
2. (a) K: [Ar] 4s¹; Ca: [Ar] 4s²; Sc: [Ar] 4s² 3d¹; Ti: [Ar] 4s² 3d²; V: [Ar] 4s² 3d³; Cr: [Ar] 4s¹ 3d⁵; Mn: [Ar] 4s² 3d⁵; Fe: [Ar] 4s² 3d⁶; Co: [Ar] 4s² 3d⁷; Ni: [Ar] 4s² 3d⁸; Cu: [Ar] 4s¹ 3d¹⁰; Zn: [Ar] 4s² 3d¹⁰
(b) Ga: [Ar] 4s² 3d¹⁰ 4p¹; Ge: [Ar] 4s² 3d¹⁰ 4p²; As: [Ar] 4s² 3d¹⁰ 4p³; Se: [Ar] 4s² 3d¹⁰ 4p⁴; Br: [Ar] 4s² 3d¹⁰ 4p⁵; Kr: [Ar] 4s² 3d¹⁰ 4p⁶
3. (a) 1s² 2s² 2p⁶ 3s² 3p⁶ 4s² 3d¹⁰ 4p⁶ 5s² 4d¹⁰ 5p⁶ 6s² 4f¹⁴ 5d¹⁰ 6p⁶ 7s² 5f¹⁴ 6d¹⁰ 7p⁶
(b) 1s² 2s² 2p⁶ 3s² 3p⁶ 4s² 3d¹⁰ 4p⁶ 5s² 4d¹⁰ 5p⁶ 6s² 4f¹⁴ 5d¹⁰ 6p⁶ 7s² 5f¹⁴ 6d¹⁰ 7p⁶
(c) 1s² 2s² 2p⁶ 3s² 3p⁶ 4s² 3d¹⁰ 4p⁶ 5s² 4d¹⁰ 5p⁶ 6s² 4f¹⁴ 5d¹⁰ 6p⁶ 7s² 5f¹⁴ 6d¹⁰ 7p⁶
4. Isotopes are atoms of the same element that have the same number of protons but different numbers of neutrons. They have the same atomic number but different mass numbers. The chemical properties of isotopes are nearly identical because they have the same electron configuration, but their physical properties, such as mass and nuclear stability, differ.
5. Hund's Rule states that electrons will fill degenerate orbitals (orbitals with the same energy) singly before pairing up. This minimizes electron-electron repulsion and results in the most stable arrangement. For example, in the 2p subshell, each of the three p orbitals will receive one electron before any orbital gets a second electron.
6. The Aufbau Principle states that electrons fill atomic orbitals of the lowest available energy levels before occupying higher levels. Electrons are added to orbitals in order of increasing energy: 1s, 2s, 2p, 3s, 3p, 4s, 3d, etc. The Pauli Exclusion Principle states that no two electrons in an atom can have the same set of four quantum numbers. This means an orbital can hold at most two electrons, and they must have opposite spins.
7. The "charge cloud" is a conceptual model representing the probability distribution of finding an electron around the nucleus. It does not describe a fixed path or orbit but rather regions where an electron is likely to be found. Classical physics cannot predict the exact position and momentum of an electron simultaneously due to the Heisenberg Uncertainty Principle, which states that the more precisely the position of a particle is known, the less precisely its momentum can be known, and vice versa. This inherent uncertainty requires a probabilistic description of electron location, hence the "charge cloud" model.
8. Four quantum numbers are necessary to fully describe the state of an electron in an atom:
- Principal quantum number (n): describes the main energy level or shell.
- Angular momentum quantum number (l): describes the shape of the orbital (subshell).
- Magnetic quantum number (mₗ): describes the orientation of the orbital in space.
- Spin quantum number (mₛ): describes the intrinsic spin of the electron (+½ or -½).
Parent Tip: Review the logic above to help your child master the concept of aufbau diagram worksheet.
