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Quizzes > Science > Chemistry

Atoms, Ions & Isotopes Quiz - Can You Spot the Difference?

What's an Ion and an Isotope? Jump In and Test Yourself!

Difficulty: Moderate
2-5mins
Learning OutcomesCheat Sheet
Paper art style atoms ions and isotopes quiz graphic on teal background with test your skills challenge

This quiz helps you master the difference between ion and isotope with quick, clear questions on atoms. Use it to practice for class, check any gaps before a test, and sharpen how you tell charge from mass changes in atoms.

Which definition best describes an ion?
Atoms of the same element with different numbers of neutrons
An atom or molecule with unequal numbers of protons and electrons
A positively charged nucleus
A neutral atom with balanced protons and electrons
An ion is formed when an atom or molecule gains or loses electrons, resulting in an unequal number of protons and electrons. This imbalance gives the species a net positive or negative charge. Ions are essential in processes like electrochemistry and biological signaling. Learn more at .
What is an isotope?
Molecules that carry a net charge
Ions with multiple charges
Atoms that have lost or gained electrons
Atoms with the same number of protons but different numbers of neutrons
Isotopes are variants of the same element that have identical proton counts but differ in neutrons. This variation changes the atomic mass without affecting chemical behavior significantly. Radioactive decay and medical imaging often utilize specific isotopes. More details at .
A cation is defined as:
An atom with extra electrons
An ion with a positive charge
An ion with a negative charge
An atom with extra neutrons
A cation results when an atom or molecule loses one or more electrons, creating a net positive charge. Common cations include Na+ and Ca2+ in biological and chemical systems. Their positive charge attracts negative species (anions) to form ionic compounds. See .
An anion is:
A neutral isotope
An ion with a positive charge
An ion with a negative charge
A radioactive isotope
An anion forms when an atom or molecule gains one or more electrons, resulting in a net negative charge. Examples include Cl? and SO4²?, which play crucial roles in physiology and industrial processes. Anions pair with cations to create ionic substances. More at .
The atomic number of an element corresponds to:
The number of neutrons in the nucleus
The number of electrons in a neutral atom
The number of protons in the nucleus
The total mass of protons and neutrons
Atomic number uniquely identifies an element and equals the count of protons in its nucleus. In a neutral atom, this also equals the number of electrons, but the defining feature is protons. Changing atomic number changes the element. Read more at .
Formation of an ion involves change in the number of:
Protons
Electrons
Neutrons
Photons
Ions form by losing or gaining electrons; protons and neutrons in the nucleus remain unchanged. Electron transfer alters the electrical charge of an atom or molecule. This process drives ionic bonding and conductivity. More details at .
Isotopes of an element differ in their number of:
Neutrons
Protons
Valence electrons
Electrons
Isotopes vary in neutron count while sharing the same proton number. This difference alters atomic mass but not chemical identity. Applications include carbon dating and nuclear power. See .
Which of the following represents a sodium ion with one extra electron?
Na2+
Na+
Na°
Na?
When sodium gains one electron, it becomes Na? with one extra electron. The common sodium cation is Na?, but adding rather than losing an electron yields the anionic form. This is less stable in typical chemistry. More at .
A calcium ion has 18 electrons. What is its charge?
2+
3+
1+
2?
Neutral calcium has 20 electrons and 20 protons. Losing two electrons yields 18 electrons with 20 protons, giving a net 2? charge. Calcium commonly forms Ca²? in biological and chemical contexts. Learn more at .
Which pair of atoms are isotopes?
Carbon-12 and Carbon-14
Potassium and Calcium
Sodium and Chlorine
Nitrogen and Neon
Carbon-12 and Carbon-14 share the same proton number (6) but differ in neutrons (6 vs 8). This makes them isotopes of the same element. Other options involve different elements entirely. More at .
How is the isotope uranium-235 represented in nuclear notation?
U-235
235U
U235
2+35U
Nuclear notation places the mass number as a superscript before the element symbol (e.g., ²³?U). The hyphen notation (U-235) is common but not true nuclear notation. Correct formatting indicates mass number distinctly. See .
Which of the following is not an example of an isotope?
H-3
He-2
C-12
H-1
Helium-2 (diproton) does not exist as a stable isotope; it's not a recognized nuclide. H-1, H-3 (tritium), and C-12 are well-known isotopes. Genuine isotopes must have valid configurations of protons and neutrons. Read more at .
Chlorine-37 has 17 protons and how many neutrons?
54
17
37
20
Mass number (37) equals protons (17) plus neutrons. Subtract 17 protons from 37 to get 20 neutrons. Correct neutron count ensures accurate mass determination. More info at .
Why do isotopes of an element exhibit nearly identical chemical properties?
Because they have different atomic numbers
Because they have different mass numbers
Because they have the same number of electrons and protons
Because they have the same number of neutrons
Chemical behavior is governed by electron configuration and proton count, which remain constant across isotopes. Differences in neutron count affect mass and nuclear properties but not chemistry. This explains why isotopes react similarly in compounds. Further reading at .
Magnesium has an isotope Magnesium-24 and Mg2+ ion. What is the charge on the ionic magnesium species?
1+
0
3+
2+
Mg²? indicates magnesium has lost two electrons relative to its neutral state. The isotope designation (24Mg) refers only to mass number, not charge. Mg²? is common in biological and geochemical processes. More at .
An isotope is represented as 14C. How many neutrons does it contain if its atomic number is 6?
20
14
6
8
Mass number (14) minus atomic number (6 protons) gives neutron count: 8. This is a standard calculation for any isotope. Accuracy here is essential in nuclear chemistry. See .
If an element has two isotopes with masses 10 (20% abundance) and 11 (80%), what is its average atomic mass?
11.2
10.8
10.2
21
Average atomic mass = (10 × 0.20) + (11 × 0.80) = 2 + 8.8 = 10.8. Weighting by natural abundance gives a realistic atomic mass. This method is used to report masses on the periodic table. More at .
A neutral atom has 15 protons, 16 neutrons, and 18 electrons. What species is this?
Phosphorus-31 with a 3? charge
Phosphorus-31 neutral
Sulfur-31 with a 2? charge
Phosphorus-15 with a 2? charge
Protons (15) define phosphorus. Neutrons (16) give mass number 31. Electrons (18) vs protons (15) yields a 3? charge. This is the phosphide isotope ³¹P³?. See .
Which analytical technique separates ions based on mass-to-charge ratio and can distinguish isotopes?
Mass spectrometry
NMR spectroscopy
UV-Vis spectroscopy
Infrared spectroscopy
Mass spectrometry ionizes samples and separates ions by mass-to-charge ratio, allowing isotope resolution. It provides accurate isotopic abundance and molecular weight data. Essential in proteomics, geochemistry, and forensics. More at .
How does isotopic substitution affect the vibrational frequency of a molecule in infrared spectroscopy?
No change in vibrational frequency
Only affects rotational but not vibrational frequency
Heavier isotope raises vibrational frequency
Heavier isotope lowers vibrational frequency
Vibrational frequency depends inversely on the square root of reduced mass. Substituting a heavier isotope increases mass, thus lowering vibration frequency. This is observed as peak shifts in IR spectra. See .
In going from a neutral atom to an anion, what happens to the atomic radius?
It oscillates unpredictably
It increases due to added electron repulsion
It decreases due to greater nuclear attraction
It remains the same
Adding electrons increases electron - electron repulsion in the outer shell, causing the electron cloud to expand. The nuclear charge is unchanged, so radius increases. This trend is seen across many anions. More at .
The nitrate ion can exist with an 18O isotope. Which notation represents this oxygen isotope?
NO3-
O18-
18O
O2-
Isotopic notation places the mass number as a prefix (e.g., ¹?O). This specifies the oxygen-18 isotope. Other formats either denote charge or molecular formula, not isotope. See .
Chlorine has two main isotopes, 35Cl and 37Cl. What pattern ratio appears in its mass spectrum?
1:3
3:1 (35Cl to 37Cl)
1:1
7:2
Natural chlorine is ~75% ³?Cl and ~25% ³?Cl, giving a 3:1 peak intensity ratio in mass spectrometry. This pattern is a classic example of isotopic abundance. Used for calibration and identification in MS. More at .
Which phenomenon arises from isotopic substitution affecting reaction rates due to bond vibration differences?
Radioactive decay
Kinetic isotope effect
Ionic dissociation
Equilibrium shift
The kinetic isotope effect occurs when bonds involving heavier isotopes vibrate at lower frequencies, altering reaction rates. It's a powerful tool for probing reaction mechanisms. Observed in hydrogen/deuterium exchange studies. Learn more at .
Which hydrogen isotope is commonly used as a non-active solvent in NMR spectroscopy to avoid interference?
Deuterium
Protium
Hydron
Tritium
Deuterium (²H) is used in NMR solvents because it resonates at a different frequency than protium (¹H), avoiding interference in the proton NMR spectrum. Its incorporation provides a lock signal for field stabilization. Tritium is radioactive and not used for this purpose. Details at .
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Study Outcomes

  1. Understand Ion and Isotope Fundamentals -

    Define what an ion is and what an isotope is, including their key characteristics and how they relate to atomic structure.

  2. Differentiate Ions from Isotopes -

    Distinguish the difference between ion and isotope by comparing electron gain or loss versus neutron variation.

  3. Analyze Atomic Transformations -

    Explain how atoms become ions through electron exchange and how isotopic forms emerge from neutron changes.

  4. Apply Concepts to Practice Questions -

    Solve quiz items and worksheet scenarios focused on atoms, ions and isotopes to reinforce your learning.

  5. Assess Your Mastery -

    Evaluate your understanding by completing targeted questions on ions, isotopes and their differences.

Cheat Sheet

  1. Definition of Ions vs. Isotopes -

    The primary difference between an ion and isotope lies in electron count versus neutron count: ions carry a net charge due to electron gain or loss, while isotopes are neutral atoms of the same element with varying neutron numbers. According to IUPAC guidelines, you can denote ions with superscripts showing charge (e.g., Na❺) and isotopes with mass numbers (e.g., ¹❴C). Remember the phrase "Ion is charged, isotope is sized" to lock in which particle changes.

  2. Electron Transfer and Ion Formation -

    Review oxidation and reduction reactions where atoms become ions: for example, Mg → Mg²❺ + 2e❻ or Cl + e❻ → Cl❻, as detailed by Khan Academy. Use the formula Q = n·F (where n is the number of electrons and F is Faraday's constant) to quantify charge transfer if needed. This solidifies how electron count changes drive ion creation in redox processes.

  3. Isotope Notation and Mass Numbers -

    Isotopes are distinguished using the notation AₓY (mass number A over atomic number x with element symbol Y), such as ¹³C or ²³❵U, following the convention in MIT OpenCourseWare. Knowing that "mass number = protons + neutrons" helps you calculate the neutron count for any isotope. Practice writing isotopic symbols to reinforce recognition.

  4. Chemical vs. Physical Property Differences -

    Though isotopes share chemical behavior, their mass differences affect physical properties like density and radioactive decay rates - for instance, heavy water (D₂O) exhibits a higher boiling point than H₂O, as noted by the US National Labs. In contrast, ions determine electrical conductivity in solutions, which is key in electrolytes and battery chemistry. Comparing these properties underscores why the difference between an ion and isotope matters in applications.

  5. Real-World Applications of Ions and Isotopes -

    Explore how isotopes like ¹❴C enable radiocarbon dating in archaeology and how ions such as Na❺ and K❺ maintain nerve impulses and fluid balance in physiology, drawing from NIH resources. An "ions isotopes and atoms worksheet" often pairs these examples to test conceptual understanding. Connecting theory to everyday uses boosts retention and confidence.

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