This question tests the skill of atomic structure and electron configuration. Atomic number 29 is copper with 29 electrons, an exception for stability. Normally [Ar] 4s² 3d⁹, but it prefers full d subshell, so [Ar] 4s¹ 3d¹⁰. This half-filled s and full d provide extra stability. A tempting distractor like A, [Ar] 4s² 3d⁹, is incorrect because it follows strict Aufbau without the exception. Recall exceptions for Cu and Cr where electron promotion stabilizes the configuration.

This question tests the skill of atomic structure and electron configuration. Atomic number 12 is magnesium with 12 electrons, filling up to $3s^2$ after [Ne]. Orbitals are filled in order: 1s, 2s, 2p, 3s, with s subshells holding 2 electrons each. The configuration is $1s^2 2s^2 2p^6 3s^2$, totaling 12 electrons. A tempting distractor like D, $1s^2 2s^2 2p^6 3p^2$, is incorrect as it places electrons in 3p before fully filling 3s, violating Aufbau. Count total electrons and ensure orbitals are filled in the correct energy order for ground state.

This question tests the skill of atomic structure and electron configuration. Atomic number 30 is zinc with 30 electrons neutrally, but R²⁺ loses 2, leaving 28. For zinc, electrons are removed from 4s, as it's higher energy in ions. From [Ar] 4s² 3d¹⁰, it becomes [Ar] 3d¹⁰. A tempting distractor like E, [Ar] 4s⁰ 3d⁸, is incorrect as it removes from d instead of s. For transition metal ions, remove from ns orbital before (n-1)d to get the correct configuration.

This question tests the skill of atomic structure and electron configuration. Atomic number 9 is fluorine with 9 electrons, filling up to $2p^5$. Orbitals fill: $1s^2$, $2s^2$, then $2p^5$, as p holds up to 6 but has only 5 here. Total is $2 + 2 + 5 = 9$. A tempting distractor like B, $1s^2 2s^2 2p^6$, is incorrect as it has 10 electrons, representing neon. Always verify the total electron count matches the atomic number for neutral atoms before assigning configurations.

This question tests the skill of atomic structure and electron configuration. The element with atomic number 26 is iron, with 26 electrons in its neutral state, but the X²⁺ ion has lost 2 electrons, leaving 24. For transition metals, electrons are removed first from the 4s orbital before the 3d, following the ion configuration rules. Thus, from neutral [Ar] 4s² 3d⁶, the ion becomes [Ar] 3d⁶. A tempting distractor like A, [Ar] 4s² 3d⁴, is incorrect as it assumes removal from 3d first, ignoring the actual ionization order. To determine ion configurations, subtract electrons from the outermost s orbital first for transition metals.

This question tests your understanding of atomic structure and electron configuration. The given configuration [Ar] 4s² 3d⁶ indicates 18 electrons from Ar, plus 2 in 4s and 6 in 3d, totaling 26 electrons. Electrons fill orbitals following Hund's rule, which states that electrons occupy orbitals singly before pairing to maximize unpaired spins. For 3d⁶, the five 3d orbitals each get one electron (5 unpaired), then the sixth pairs one, leaving 4 unpaired electrons total, with the 4s² being paired. A tempting distractor is choice B (2), which might come from mistakenly thinking all d electrons pair up early, but Hund's rule requires single occupancy first. To find unpaired electrons, draw orbital diagrams and apply Hund's rule after determining the configuration.

This question tests your understanding of atomic structure and electron configuration. Element Z with atomic number 35 is bromine, neutral configuration [Ar] 4s² 3d¹⁰ 4p⁵, with 35 electrons. For the Z⁻ anion, add one electron to reach 36, filling the 4p subshell to 4p⁶, resulting in [Ar] 4s² 3d¹⁰ 4p⁶. This is determined by adding the extra electron to the next available orbital following the Aufbau principle. A tempting distractor is choice A, which is the neutral configuration, but it lacks the extra electron for the anion. For ions, adjust the electron count from the neutral atom and fill or remove from the appropriate subshells.

This question tests your understanding of atomic structure and electron configuration. For a neutral atom with atomic number 17, there are 17 protons and thus 17 electrons to place in orbitals. Electrons fill orbitals starting from the lowest energy level, following the Aufbau principle: first 1s (2 electrons), then 2s (2), 2p (6), 3s (2), and finally 3p with the remaining 5 electrons. This results in the configuration 1s² 2s² 2p⁶ 3s² 3p⁵, which matches choice A. A tempting distractor is choice B, which has 3p⁶, but that would be for 18 electrons, like argon, not 17. Always count the total electrons based on the atomic number for neutral atoms and fill orbitals in order of increasing energy.

This question tests your understanding of atomic structure and electron configuration. An atom with atomic number 24 has 24 electrons to distribute. Normally, electrons fill 4s before 3d, but chromium is an exception where [Ar] 4s¹ 3d⁵ provides extra stability due to half-filled subshells. This configuration is determined by recognizing known exceptions for elements like Cr and Cu. A tempting distractor is choice A ([Ar] 4s² 3d⁴), which follows the standard order but ignores the exception for stability. Memorize exceptions for transition metals and prioritize half-filled or fully filled subshells when applicable.

This question tests your understanding of atomic structure and electron configuration. The configuration [Ne] 3s² 3p³ indicates 10 electrons from Ne, plus 2 in 3s and 3 in 3p, totaling 15 electrons. Hund's rule dictates that the 3p electrons occupy separate orbitals singly, resulting in three unpaired electrons. The 3s² is fully paired, so only the 3p contributes unpaired electrons. A tempting distractor is choice E (5), which might assume all electrons are unpaired, but pairing occurs in filled subshells. Use orbital diagrams to visualize electron pairing and count unpaired ones per Hund's rule.