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.
За това тесте
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.
Карти в това тесте
Карта 1
Въпрос
For a monatomic ion, how do atomic number Z and signed charge q give its electron count?
Отговор
Electron count = Z − q. Use q = +2 for a 2+ ion and q = −2 for a 2− ion.
Карта 2
Въпрос
When an atom forms a monatomic ion by gaining or losing electrons, what happens to its proton count?
Отговор
It stays the same. Ion formation changes the electron count, not the element’s atomic number.
Карта 3
Въпрос
Na⁺, Z = 11: electron count?
Отговор
10 electrons. The 1+ charge means one fewer electron than the 11 protons.
Карта 4
Въпрос
What does isoelectronic mean for the closed-shell monatomic ions compared here?
Отговор
They have the same electron configuration. For these ground-state 10- or 18-electron ions, matching electron totals gives the matching configuration.
Карта 5
Въпрос
O²⁻, Z = 8: electron count?
Отговор
10 electrons. The 2− charge means two more electrons than the eight protons.
Карта 6
Въпрос
A magnesium ion has 12 protons and 10 electrons. What is its signed charge?
Отговор
2+. There are two more protons than electrons: 12 − 10 = +2.
Карта 7
Въпрос
Cl⁻, Z = 17: electron count?
Отговор
18 electrons. A 1− ion has one more electron than its proton count.
Карта 8
Въпрос
O²⁻ (Z = 8) and Mg²⁺ (Z = 12) both have 10 electrons. Which has the smaller ionic radius?
Отговор
Mg²⁺. With the same electron configuration, its greater proton count pulls the electron cloud closer.
Карта 9
Въпрос
Al³⁺, Z = 13: electron count?
Отговор
10 electrons. Subtract the positive charge: 13 − 3 = 10.
Карта 10
Въпрос
Which ion has the same electron configuration as Na⁺ (Z = 11): F⁻ (Z = 9), K⁺ (Z = 19), or Ca²⁺ (Z = 20)?
Отговор
F⁻. Both F⁻ and Na⁺ have 10 electrons; K⁺ and Ca²⁺ each have 18.
Карта 11
Въпрос
A learner writes: “P³⁻ has 15 − 3 = 12 electrons.” With Z = 15, repair the calculation.
Отговор
15 + 3 = 18 electrons. A negative charge adds electrons to the neutral count.
Карта 12
Въпрос
A monatomic ion has more electrons than protons. What sign must its charge have?
Отговор
Negative. The excess electrons give a net negative charge.
Карта 13
Въпрос
N³⁻ (Z = 7) and Na⁺ (Z = 11) both have 10 electrons. Which has the larger ionic radius?
Отговор
N³⁻. Its smaller proton count holds the same electron configuration less tightly.
Карта 14
Въпрос
N³⁻, Z = 7: electron count?
Отговор
10 electrons. Add three for the 3− charge: 7 + 3 = 10.
Карта 15
Въпрос
Does the isoelectronic radius rule justify ranking F⁻ (Z = 9) and Cl⁻ (Z = 17) by proton count alone?
Отговор
No. F⁻ has 10 electrons and Cl⁻ has 18, so their configurations differ. This rule alone does not establish their order.
Карта 16
Въпрос
Which aluminium ion has 13 protons and 10 electrons? Give its symbol and charge.
Отговор
Al³⁺. The three-electron deficit gives a 3+ charge.
Карта 17
Въпрос
All three ions have 10 electrons. Rank O²⁻ (Z = 8), Mg²⁺ (Z = 12), and F⁻ (Z = 9) by increasing ionic radius.
Отговор
Mg²⁺ < F⁻ < O²⁻. Increasing radius follows decreasing proton count within this series.
Карта 18
Въпрос
S²⁻, Z = 16: electron count?
Отговор
18 electrons. Add two for the 2− charge: 16 + 2 = 18.
Карта 19
Въпрос
A learner says Na⁺ (Z = 11) and Al³⁺ (Z = 13) have equal radii because both have 10 electrons. Repair the conclusion.
Отговор
Al³⁺ has the smaller radius. Equal electron configurations do not mean equal sizes; Al³⁺ has the greater nuclear charge.
Карта 20
Въпрос
Which ions form the 18-electron group: P³⁻ (Z = 15), Mg²⁺ (Z = 12), Cl⁻ (Z = 17), and S²⁻ (Z = 16)?
Отговор
P³⁻, Cl⁻, and S²⁻. Each has 18 electrons; Mg²⁺ has 10.
Карта 21
Въпрос
O²⁻ (Z = 8) and F⁻ (Z = 9) both have 10 electrons. Which has the larger ionic radius?
Отговор
O²⁻. Its eight protons attract the same electron configuration less strongly than the nine protons in F⁻.
Карта 22
Въпрос
A phosphorus ion has 15 protons and 18 electrons. What is its signed charge?
Отговор
3−. Three excess electrons give a charge of −3.
Карта 23
Въпрос
For 10-electron ions, a learner gives this increasing-radius order: N³⁻ < Na⁺ < Al³⁺. Z values are 7, 11, and 13. Repair the order.
Отговор
Al³⁺ < Na⁺ < N³⁻. The greatest proton count gives the smallest radius in this series.
Карта 24
Въпрос
Ca²⁺, Z = 20: electron count?
Отговор
18 electrons. Subtract two for the 2+ charge: 20 − 2 = 18.
Карта 25
Въпрос
Do an ion’s proton and electron counts give its exact ionic radius in picometres?
Отговор
No. They support a qualitative comparison within a matching-configuration series, not an exact radius value.
Карта 26
Въпрос
K⁺ (Z = 19) and Ca²⁺ (Z = 20) both have 18 electrons. Which has the smaller ionic radius?
Отговор
Ca²⁺. Its extra proton attracts the same electron configuration more strongly.
Карта 27
Въпрос
A learner groups F⁻ (Z = 9) with Cl⁻ (Z = 17) as isoelectronic because both are 1−. Repair the grouping claim.
Отговор
They are not isoelectronic. F⁻ has 10 electrons and Cl⁻ has 18; the same ionic charge does not guarantee the same configuration.
Карта 28
Въпрос
A sulfur ion has 16 protons and 18 electrons. What is its signed charge?
Отговор
2−. It has two more electrons than protons.
Карта 29
Въпрос
All three ions have 18 electrons. Rank Cl⁻ (Z = 17), S²⁻ (Z = 16), and Ca²⁺ (Z = 20) by increasing ionic radius.
Отговор
Ca²⁺ < Cl⁻ < S²⁻. Within the shared configuration, radius increases as proton count decreases.
Карта 30
Въпрос
K⁺, Z = 19: electron count?
Отговор
18 electrons. A 1+ charge removes one electron from the neutral count.
Карта 31
Въпрос
A learner says Mg²⁺ has 12 electrons because magnesium keeps its 12 protons when it ionizes. Repair the electron count.
Отговор
10 electrons. The 12 protons stay, while a 2+ charge means two fewer electrons.
Карта 32
Въпрос
Which nitrogen ion has 7 protons and 10 electrons? Give its symbol and charge.
Отговор
N³⁻. Three excess electrons give a 3− charge.
Карта 33
Въпрос
Are N³⁻ (Z = 7) and F⁻ (Z = 9) isoelectronic in their ground states?
Отговор
Yes. Each has 10 electrons and the same closed-shell configuration.
Карта 34
Въпрос
All three ions have 18 electrons. Rank S²⁻ (Z = 16), K⁺ (Z = 19), and P³⁻ (Z = 15) by decreasing ionic radius.
Отговор
P³⁻ > S²⁻ > K⁺. Within this series, the ion with the fewest protons has the largest radius.
Карта 35
Въпрос
A calcium ion has 20 protons and 18 electrons. A learner labels it Ca²⁻. Repair the charge sign.
Отговор
Ca²⁺. The ion has two more protons than electrons, so the charge is positive.
Карта 36
Въпрос
Can you apply the isoelectronic radius rule to Mg²⁺ (Z = 12) and Ca²⁺ (Z = 20) just because both have charge 2+?
Отговор
No. Mg²⁺ has 10 electrons and Ca²⁺ has 18. A different comparison is needed; sharing a charge does not make this rule applicable.
Карта 37
Въпрос
Which ion breaks the 10-electron group: O²⁻ (Z = 8), Ca²⁺ (Z = 20), F⁻ (Z = 9), or Mg²⁺ (Z = 12)?
Отговор
Ca²⁺. It has 18 electrons; the other three each have 10.
Карта 38
Въпрос
A chlorine ion has 17 protons and 18 electrons. What is its signed charge?
Отговор
1−. One excess electron gives a charge of −1.
Карта 39
Въпрос
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.
Отговор
O²⁻ is larger. Within the same configuration, its smaller proton count gives a weaker nuclear pull and a larger electron cloud.
Карта 40
Въпрос
Al³⁺ (Z = 13) and Mg²⁺ (Z = 12) both have 10 electrons. Which has the smaller ionic radius?
Отговор
Al³⁺. It has more protons pulling on the same electron configuration.
Карта 41
Въпрос
A solution ranks S²⁻ (Z = 16) and Na⁺ (Z = 11) by proton count alone. Which required check was skipped?
Отговор
Whether the electron configurations match. S²⁻ has 18 electrons and Na⁺ has 10, so the isoelectronic radius rule cannot justify that ranking.
Карта 42
Въпрос
Can a qualitative ionic-radius rank, with no element, charge, or candidate list, uniquely identify an ion?
Отговор
No. A size rank alone does not fix an element or charge. Identification needs further constraints, such as proton and electron counts.
42 карти
Isoelectronic Ion Flashcards: Electron Counts & Radius Ranking
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