Isoelectronic Ion Flashcards: Electron Counts & Radius Ranking
Count electrons, find matching ion configurations, rank ionic radii, and repair common charge and ordering errors with 42 short chemistry flashcards.
เกี่ยวกับชุดการ์ดนี้
Practice isoelectronic ions with 42 short English flashcards. Work with familiar monatomic ground-state ions in the 10-electron [Ne] and 18-electron [Ar] groups: N³⁻, O²⁻, F⁻, Na⁺, Mg²⁺, Al³⁺, P³⁻, S²⁻, Cl⁻, K⁺, and Ca²⁺. Atomic number Z is supplied whenever counting is the task.
The cards practice ion and Z → electron count, small list → matching-configuration group or outlier, confirmed isoelectronic pair or set → qualitative radius comparison, and constrained proton/electron counts → charge or ion symbol. Short error-repair cards address sign mistakes, equal-count/equal-size confusion, incorrect groupings, reversed orders, and skipped configuration checks. A few evidence-limit questions test what this rule can establish. Answers start with the result and give a brief explanation.
The sequence starts with charge bookkeeping and unchanged nuclei, introduces the 10-electron group, then brings in the 18-electron group before interleaving comparisons, constrained inverses, and repairs. Closely related variants are separated. Numerical radii, neutral noble-gas radius comparisons, full electron-configuration derivation, transition-metal and coordination cases, molecular species, broad periodic trends, isotope drills, and full-course or exam coverage are excluded to keep each decision short and well defined. Unconstrained radius → ion identification and exhaustive reverse/permutation cards are excluded because they do not provide one clear answer.
Original questions, explanations, organization, and metadata were written with AI assistance from common scientific facts, with factual checks against Purdue’s isoelectronic glossary, Purdue’s ionic-size lesson, and NIST’s atomic-number table. The cover is an original AI-generated conceptual illustration, not a particle-count or radius-scale diagram. CC0 1.0 applies to the original deck text, organization, metadata, and cover to the extent applicable rights exist. Scientific facts are not owned; referenced works retain their own rights. No source or competitor prose, exercises, tables, or diagrams are reproduced.
An independent learning resource with no claimed curriculum or exam alignment, affiliation, or endorsement.
การ์ดในชุดการ์ดนี้
การ์ด 1
คำถาม
For a monatomic ion, how do atomic number Z and signed charge q give its electron count?
คำตอบ
Electron count = Z − q. Use q = +2 for a 2+ ion and q = −2 for a 2− ion.
การ์ด 2
คำถาม
When an atom forms a monatomic ion by gaining or losing electrons, what happens to its proton count?
คำตอบ
It stays the same. Ion formation changes the electron count, not the element’s atomic number.
การ์ด 3
คำถาม
Na⁺, Z = 11: electron count?
คำตอบ
10 electrons. The 1+ charge means one fewer electron than the 11 protons.
การ์ด 4
คำถาม
What does isoelectronic mean for the closed-shell monatomic ions compared here?
คำตอบ
They have the same electron configuration. For these ground-state 10- or 18-electron ions, matching electron totals gives the matching configuration.
การ์ด 5
คำถาม
O²⁻, Z = 8: electron count?
คำตอบ
10 electrons. The 2− charge means two more electrons than the eight protons.
การ์ด 6
คำถาม
A magnesium ion has 12 protons and 10 electrons. What is its signed charge?
คำตอบ
2+. There are two more protons than electrons: 12 − 10 = +2.
การ์ด 7
คำถาม
Cl⁻, Z = 17: electron count?
คำตอบ
18 electrons. A 1− ion has one more electron than its proton count.
การ์ด 8
คำถาม
O²⁻ (Z = 8) and Mg²⁺ (Z = 12) both have 10 electrons. Which has the smaller ionic radius?
คำตอบ
Mg²⁺. With the same electron configuration, its greater proton count pulls the electron cloud closer.
การ์ด 9
คำถาม
Al³⁺, Z = 13: electron count?
คำตอบ
10 electrons. Subtract the positive charge: 13 − 3 = 10.
การ์ด 10
คำถาม
Which ion has the same electron configuration as Na⁺ (Z = 11): F⁻ (Z = 9), K⁺ (Z = 19), or Ca²⁺ (Z = 20)?
คำตอบ
F⁻. Both F⁻ and Na⁺ have 10 electrons; K⁺ and Ca²⁺ each have 18.
การ์ด 11
คำถาม
A learner writes: “P³⁻ has 15 − 3 = 12 electrons.” With Z = 15, repair the calculation.
คำตอบ
15 + 3 = 18 electrons. A negative charge adds electrons to the neutral count.
การ์ด 12
คำถาม
A monatomic ion has more electrons than protons. What sign must its charge have?
คำตอบ
Negative. The excess electrons give a net negative charge.
การ์ด 13
คำถาม
N³⁻ (Z = 7) and Na⁺ (Z = 11) both have 10 electrons. Which has the larger ionic radius?
คำตอบ
N³⁻. Its smaller proton count holds the same electron configuration less tightly.
การ์ด 14
คำถาม
N³⁻, Z = 7: electron count?
คำตอบ
10 electrons. Add three for the 3− charge: 7 + 3 = 10.
การ์ด 15
คำถาม
Does the isoelectronic radius rule justify ranking F⁻ (Z = 9) and Cl⁻ (Z = 17) by proton count alone?
คำตอบ
No. F⁻ has 10 electrons and Cl⁻ has 18, so their configurations differ. This rule alone does not establish their order.
การ์ด 16
คำถาม
Which aluminium ion has 13 protons and 10 electrons? Give its symbol and charge.
คำตอบ
Al³⁺. The three-electron deficit gives a 3+ charge.
การ์ด 17
คำถาม
All three ions have 10 electrons. Rank O²⁻ (Z = 8), Mg²⁺ (Z = 12), and F⁻ (Z = 9) by increasing ionic radius.
คำตอบ
Mg²⁺ < F⁻ < O²⁻. Increasing radius follows decreasing proton count within this series.
การ์ด 18
คำถาม
S²⁻, Z = 16: electron count?
คำตอบ
18 electrons. Add two for the 2− charge: 16 + 2 = 18.
การ์ด 19
คำถาม
A learner says Na⁺ (Z = 11) and Al³⁺ (Z = 13) have equal radii because both have 10 electrons. Repair the conclusion.
คำตอบ
Al³⁺ has the smaller radius. Equal electron configurations do not mean equal sizes; Al³⁺ has the greater nuclear charge.
การ์ด 20
คำถาม
Which ions form the 18-electron group: P³⁻ (Z = 15), Mg²⁺ (Z = 12), Cl⁻ (Z = 17), and S²⁻ (Z = 16)?
คำตอบ
P³⁻, Cl⁻, and S²⁻. Each has 18 electrons; Mg²⁺ has 10.
การ์ด 21
คำถาม
O²⁻ (Z = 8) and F⁻ (Z = 9) both have 10 electrons. Which has the larger ionic radius?
คำตอบ
O²⁻. Its eight protons attract the same electron configuration less strongly than the nine protons in F⁻.
การ์ด 22
คำถาม
A phosphorus ion has 15 protons and 18 electrons. What is its signed charge?
คำตอบ
3−. Three excess electrons give a charge of −3.
การ์ด 23
คำถาม
For 10-electron ions, a learner gives this increasing-radius order: N³⁻ < Na⁺ < Al³⁺. Z values are 7, 11, and 13. Repair the order.
คำตอบ
Al³⁺ < Na⁺ < N³⁻. The greatest proton count gives the smallest radius in this series.
การ์ด 24
คำถาม
Ca²⁺, Z = 20: electron count?
คำตอบ
18 electrons. Subtract two for the 2+ charge: 20 − 2 = 18.
การ์ด 25
คำถาม
Do an ion’s proton and electron counts give its exact ionic radius in picometres?
คำตอบ
No. They support a qualitative comparison within a matching-configuration series, not an exact radius value.
การ์ด 26
คำถาม
K⁺ (Z = 19) and Ca²⁺ (Z = 20) both have 18 electrons. Which has the smaller ionic radius?
คำตอบ
Ca²⁺. Its extra proton attracts the same electron configuration more strongly.
การ์ด 27
คำถาม
A learner groups F⁻ (Z = 9) with Cl⁻ (Z = 17) as isoelectronic because both are 1−. Repair the grouping claim.
คำตอบ
They are not isoelectronic. F⁻ has 10 electrons and Cl⁻ has 18; the same ionic charge does not guarantee the same configuration.
การ์ด 28
คำถาม
A sulfur ion has 16 protons and 18 electrons. What is its signed charge?
คำตอบ
2−. It has two more electrons than protons.
การ์ด 29
คำถาม
All three ions have 18 electrons. Rank Cl⁻ (Z = 17), S²⁻ (Z = 16), and Ca²⁺ (Z = 20) by increasing ionic radius.
คำตอบ
Ca²⁺ < Cl⁻ < S²⁻. Within the shared configuration, radius increases as proton count decreases.
การ์ด 30
คำถาม
K⁺, Z = 19: electron count?
คำตอบ
18 electrons. A 1+ charge removes one electron from the neutral count.
การ์ด 31
คำถาม
A learner says Mg²⁺ has 12 electrons because magnesium keeps its 12 protons when it ionizes. Repair the electron count.
คำตอบ
10 electrons. The 12 protons stay, while a 2+ charge means two fewer electrons.
การ์ด 32
คำถาม
Which nitrogen ion has 7 protons and 10 electrons? Give its symbol and charge.
คำตอบ
N³⁻. Three excess electrons give a 3− charge.
การ์ด 33
คำถาม
Are N³⁻ (Z = 7) and F⁻ (Z = 9) isoelectronic in their ground states?
คำตอบ
Yes. Each has 10 electrons and the same closed-shell configuration.
การ์ด 34
คำถาม
All three ions have 18 electrons. Rank S²⁻ (Z = 16), K⁺ (Z = 19), and P³⁻ (Z = 15) by decreasing ionic radius.
คำตอบ
P³⁻ > S²⁻ > K⁺. Within this series, the ion with the fewest protons has the largest radius.
การ์ด 35
คำถาม
A calcium ion has 20 protons and 18 electrons. A learner labels it Ca²⁻. Repair the charge sign.
คำตอบ
Ca²⁺. The ion has two more protons than electrons, so the charge is positive.
การ์ด 36
คำถาม
Can you apply the isoelectronic radius rule to Mg²⁺ (Z = 12) and Ca²⁺ (Z = 20) just because both have charge 2+?
คำตอบ
No. Mg²⁺ has 10 electrons and Ca²⁺ has 18. A different comparison is needed; sharing a charge does not make this rule applicable.
การ์ด 37
คำถาม
Which ion breaks the 10-electron group: O²⁻ (Z = 8), Ca²⁺ (Z = 20), F⁻ (Z = 9), or Mg²⁺ (Z = 12)?
คำตอบ
Ca²⁺. It has 18 electrons; the other three each have 10.
การ์ด 38
คำถาม
A chlorine ion has 17 protons and 18 electrons. What is its signed charge?
คำตอบ
1−. One excess electron gives a charge of −1.
การ์ด 39
คำถาม
A learner says O²⁻ is smaller than F⁻ because it is more negative. Both have 10 electrons; Z is 8 for O and 9 for F. Repair the comparison.
คำตอบ
O²⁻ is larger. Within the same configuration, its smaller proton count gives a weaker nuclear pull and a larger electron cloud.
การ์ด 40
คำถาม
Al³⁺ (Z = 13) and Mg²⁺ (Z = 12) both have 10 electrons. Which has the smaller ionic radius?
คำตอบ
Al³⁺. It has more protons pulling on the same electron configuration.
การ์ด 41
คำถาม
A solution ranks S²⁻ (Z = 16) and Na⁺ (Z = 11) by proton count alone. Which required check was skipped?
คำตอบ
Whether the electron configurations match. S²⁻ has 18 electrons and Na⁺ has 10, so the isoelectronic radius rule cannot justify that ranking.
การ์ด 42
คำถาม
Can a qualitative ionic-radius rank, with no element, charge, or candidate list, uniquely identify an ion?
คำตอบ
No. A size rank alone does not fix an element or charge. Identification needs further constraints, such as proton and electron counts.
42 การ์ด
Isoelectronic Ion Flashcards: Electron Counts & Radius Ranking
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