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Quizzes > Science

Polyatomic Ions Quiz: Names, Formulas, and Charges

Quick, free polyatomic ion test with instant results.

Editorial: Review CompletedCreated By: Honesttlly InsaneUpdated Aug 27, 2025
Difficulty: Moderate
2-5mins
Learning OutcomesCheat Sheet
Paper art illustration for polyatomic ions quiz on a sky blue background

This polyatomic ions quiz helps you recognize charged groups by name, formula, and typical charge, with instant feedback on every question. Use it to spot gaps fast and strengthen recall for class or exams. When you are ready for more, try the common polyatomic ions quiz, the naming polyatomic ions quiz, or the polyatomic ions charge quiz.

What is the charge on the sulfate ion?
-2
+2
-1
+1
The sulfate ion is SO4 with a net charge of -2 because each oxygen carries a -2 oxidation state balanced by the +6 of sulfur, resulting in SO4 2-. This is a fundamental polyatomic ion commonly encountered in inorganic chemistry. The charge arises from the overall electron count compared to the neutral atoms.
Which formula represents the nitrate ion?
NO3?
NO3²?
N2O3
NO2?
The nitrate ion has the formula NO3?, composed of one nitrogen atom bonded to three oxygens and carrying a -1 charge. Its resonance-stabilized structure distributes the negative charge equally among the oxygen atoms. Nitrate is a key ion in fertilizers and environmental chemistry.
What is the name of the ion with formula NH4??
Nitride
Ammonium
Amide
Hydrazinium
The NH4? ion is called ammonium and is formed by the protonation of ammonia (NH3). It carries a +1 charge and is a common cation in acid - base chemistry. Ammonium salts are widely used in fertilizers and cleaning agents.
Which of the following is the carbonate ion?
C3O2
CO2²?
CO3²?
CH3COO?
The carbonate ion is CO3²?, featuring one carbon atom double-bonded to one oxygen and single-bonded to two other oxygens, with a total -2 charge. It is a key component in carbonated beverages and geological minerals like limestone. Its resonance structures stabilize the negative charge.
What is the formula for the phosphate ion?
PO3³?
PO4²?
PO4³?
P2O7??
Phosphate is PO4³?, consisting of one phosphorus atom in the center of a tetrahedral arrangement with four oxygens, carrying a -3 charge. Phosphate is crucial for biological molecules like DNA and ATP. The three negative charges come from the oxygen atoms that have gained extra electrons.
The charge on the hydroxide ion is:
OH?
O??
OH²?
OH?
The hydroxide ion, OH?, consists of one oxygen and one hydrogen carrying a net -1 charge. It is a strong base found in substances like sodium hydroxide. In aqueous solutions, it accepts protons to form water.
Identify the chlorate ion.
ClO?
ClO??
ClO??
ClO??
Chlorate is ClO??, composed of one chlorine atom bonded to three oxygens with a -1 charge. It is widely used in bleaching, disinfectants, and herbicides. Chlorate's resonance structures distribute the negative charge over the oxygen atoms.
Which species below is a polyatomic ion?
Cl?
Na?
SO?²?
Mg²?
SO?²? (sulfate) is a polyatomic ion made of one sulfur and four oxygens carrying a -2 charge. Polyatomic ions consist of multiple atoms bonded together that act as a single charged unit. Chloride (Cl?) and sodium (Na?) are single-atom ions.
What is the common name for HCO???
Hydroxide
Bicarbonate
Carbonate
Formate
HCO?? is commonly known as bicarbonate or hydrogen carbonate. It is the conjugate base of carbonic acid and acts as a buffer in blood and other systems. Bicarbonate plays a crucial role in maintaining pH balance.
Which formula corresponds to the hydrogen phosphate ion?
HPO?²?
PO?³?
H?PO??
HP?O?³?
Hydrogen phosphate, HPO?²?, is the conjugate base of dihydrogen phosphate and can act as a base in the phosphate buffer system. It has one proton less than H?PO??. This ion is important in biological buffering.
What is the charge on the permanganate ion?
MnO?²?
MnO?
MnO??
MnO??
Permanganate is MnO??, featuring manganese in the +7 oxidation state bonded to four oxygens. It is a strong oxidizing agent in acidic solution. The single negative charge comes from the extra electron beyond neutrality.
What is the formula for the dichromate ion?
CrO?²?
Cr?O?²?
CrO?²?
Cr?O??
Dichromate is Cr?O?²?, composed of two chromium atoms each in the +6 oxidation state joined by oxygen bridges. In acidic solution, dichromate and chromate ions interconvert depending on pH. It's widely used in analytical chemistry.
Which ion is the conjugate base of sulfuric acid?
SO?²?
H?SO?
SO?²?
HSO??
HSO?? (hydrogen sulfate or bisulfate) is the conjugate base of sulfuric acid (H?SO?), formed after losing one proton. It still can lose another proton to form SO?²?. This ion is important in acid - base titrations.
What is the chemical formula for the thiosulfate ion?
S?O?²?
SO?²?
S?O?²?
SO?²?
Thiosulfate is S?O?²?, where one sulfate oxygen is replaced by a sulfur atom. It's used in photographic fixing and gold extraction. Its structure shows resonance between the two sulfur atoms and oxygens.
Which of these ions contains nitrogen?
SO?²?
CO?²?
NO??
ClO??
NO?? is the nitrite ion, containing nitrogen bonded to two oxygens with a -1 charge. Nitrogen is absent in carbonate, sulfate, and perchlorate. Nitrite is an intermediate in nitrogen cycling in soils and water.
What is the oxidation state of sulfur in the sulfite ion, SO?²??
+2
+4
+6
+5
In SO?²?, each oxygen is -2 for a total of -6. The overall charge is -2, so sulfur must be +4 to balance. This +4 state makes sulfite a reducing agent in some reactions.
What is the formula for the hypochlorite ion?
ClO??
ClO??
ClO??
ClO?
Hypochlorite is ClO?, used in bleaching and disinfection. It is the conjugate base of hypochlorous acid (HOCl). Its chemistry is crucial in water treatment and household cleaners.
What is the formula for the acetate ion?
C?H?O?
C?H?O?²?
COO?
CH?COO?
Acetate is CH?COO?, consisting of two carbons, three hydrogens, and two oxygens with a -1 charge. It's the conjugate base of acetic acid (vinegar). Acetate is fundamental in organic reactions and metabolism.
Which of the following is the triiodide ion?
I??
I??
I?²?
I??
Triiodide is I??, formed by the association of I? with I? in solution, carrying a -1 charge. It's used in iodometry titrations and shows a characteristic dark color. This complex ion demonstrates halogen coordination chemistry.
What is the molecular geometry of the phosphate ion?
Tetrahedral
Octahedral
Bent
Trigonal planar
Phosphate (PO?³?) has a tetrahedral geometry with four oxygen atoms symmetrically arranged around phosphorus. This arises from sp³ hybridization of the phosphorus center. The shape is crucial for its function in biological molecules like ATP.
What is the oxidation state of chromium in the dichromate ion, Cr?O?²??
+4
+2
+6
+3
In Cr?O?²?, seven oxygens contribute -14 total, and the overall charge is -2, so the two chromium atoms together must be +12, giving each Cr a +6 oxidation state. Dichromate is a strong oxidizing agent in acid.
What is the formula for the oxalate ion?
C?O?²?
C?O?²?
CO?²?
C?O?²?
Oxalate is C?O?²?, consisting of two carboxylate groups linked together. It often forms strong complexes with metal ions like Ca²? and Fe³?. Oxalate is important in both biological systems and coordination chemistry.
What is the name of the CrO?²? ion?
Perchromate
Dichromate
Chromate
Trichromate
CrO?²? is called chromate, featuring chromium in a +6 oxidation state bonded to four oxygens in a tetrahedral layout. Chromate and dichromate interconvert depending on pH. This ion is used in pigments and corrosion inhibitors.
What is the formula for the thiocyanate ion?
CNS?
SCN?
CSN²?
S?CN³?
Thiocyanate, SCN?, contains sulfur, carbon, and nitrogen with a -1 charge. It forms complexes with metals and is used in chemical analysis. The ion shows resonance between S - C - N and S=C=N forms.
What is the molecular shape of the sulfite ion, SO?²??
Bent
Tetrahedral
Trigonal planar
Trigonal pyramidal
SO?²? has three bonding pairs and one lone pair on the sulfur, resulting in a trigonal pyramidal shape. This is predicted by VSEPR theory for AX?E molecules. The lone pair slightly distorts bond angles from 109.5°.
What is the formula for the superoxide ion?
O?²?
O??
O?²?
O?
Superoxide is O??, containing two oxygens sharing an extra electron. It is a reactive oxygen species important in biology and combustion. The species often appears in alkali superoxide salts like KO?.
Which polyatomic ion has the highest negative charge among these?
Carbonate
Nitrate
Sulfate
Phosphate
Phosphate (PO?³?) carries a -3 charge, which is higher in magnitude than sulfate (SO?²?), carbonate (CO?²?), and nitrate (NO??). This extra negative charge reflects the removal of three protons from phosphoric acid. Phosphate's charge makes it vital for energy transfer in cells.
Which polyatomic ion can act as both an acid and a base in the phosphate buffering system?
PO?³?
H?PO?
HPO?²?
H?PO??
HPO?²? (hydrogen phosphate) can accept a proton to become H?PO?? or donate a proton to become PO?³?, making it amphiprotic in the phosphate buffer system. This dual role is critical in maintaining physiological pH. The Henderson - Hasselbalch equation describes its buffering behavior.
In alkaline redox titrations, which polyatomic ion serves as the primary oxidizing agent?
MnO??
NO??
Cr?O?²?
ClO??
In alkaline solutions, permanganate (MnO??) acts as a strong oxidizer, often reduced to MnO? (solid). The MnO??/MnO? reaction is used in redox titrations under basic conditions. The purple permanganate color disappears at endpoint.
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Study Outcomes

  1. Identify Common Polyatomic Ions -

    Recognize the chemical formulas and charges of frequently encountered ions such as hydroxide (OH - ), nitrate (NO₃ - ), sulfate (SO₄² - ) and others to strengthen your foundational knowledge.

  2. Name Ions from Formulas -

    Convert given chemical formulas into proper ion names, including more complex species like dichromate (Cr₂O₇² - ), ensuring accurate nomenclature practice.

  3. Differentiate Similar Ions -

    Distinguish between closely related ions - such as sulfate vs. sulfite and nitrate vs. nitrite - to avoid common naming and charge errors.

  4. Apply Charge Balancing -

    Use your understanding of polyatomic ion charges to predict and write correct formulas for ionic compounds, ensuring overall charge neutrality.

  5. Enhance Quiz Recall Speed -

    Improve your quick-identification skills under polyatomic ions quiz conditions to solve questions more efficiently and accurately.

  6. Monitor Progress and Confidence -

    Track your performance throughout the free polyatomic ions quiz to build confidence and identify areas for further practice.

Cheat Sheet

  1. Memorize Core Formulas and Charges -

    Familiarize yourself with the eight most common ions - nitrate (NO₃❻), sulfate (SO₄²❻), phosphate (PO₄³❻), carbonate (CO₃²❻), hydroxide (OH❻), ammonium (NH₄❺), acetate (C₂H₃O₂❻) and chromate (CrO₄²❻). Use the "Nick the Camel ATE Clams for Supper in Phoenix" mnemonic to recall NO₃❻, CO₃²❻, ClO₃❻, SO₄²❻ and PO₄³❻. Confidence builds when you can write each formula without hesitation - perfect prep for any polyatomic ions quiz.

  2. Understand Naming Rules and Suffixes -

    Learn IUPAC conventions: the "-ate" ending denotes more oxygens than "-ite" (e.g., sulfate vs. sulfite), and "hypo-"/"per-" signal fewer or greater oxygens respectively (hypochlorite ClO❻, perchlorate ClO₄❻). Remember hydrogen (bi-) prefixes add H❺ (bicarbonate HCO₃❻, bisulfate HSO₄❻). Mastery of these patterns will make question stems in your polyatomic ions practice feel straightforward.

  3. Apply Charge-Balance in Compound Formation -

    Use the crossover method to balance charges: Al³❺ with PO₄³❻ becomes AlPO₄, and Mg²❺ with NO₃❻ gives Mg(NO₃)₂. Practice by writing formulas for combinations like Ca²❺/CO₃²❻ or NH₄❺/SO₄²❻ until it's second nature. Accurate charge balancing is crucial for acing a polyatomic ion quiz under time pressure.

  4. Leverage Solubility and Reaction Rules -

    Know that all nitrates and ammonium salts are soluble, while most hydroxides are insoluble except those of Group 1 and Ba²❺ (per University of Waterloo guidelines). Use these rules to predict precipitates - e.g., mixing NaOH with FeCl₃ yields Fe(OH)₃(s). Being able to anticipate products boosts your score on reaction-based quiz questions.

  5. Use Active Recall and Spaced Repetition -

    Create digital flashcards or use free polyatomic ions game apps from sites like Purdue University to quiz yourself daily. Schedule reviews at increasing intervals - 1 day, 3 days, 1 week - to cement retention. Consistent, self-testing practice is statistically proven to outperform passive reading (see journals from the American Chemical Society).

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