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Quizzes > Science > Chemistry

Ready to Ace Chemistry Unit 2? Take the Test!

Dive into our chemistry unit 2 practice test for a thorough chem unit 2 review!

Difficulty: Moderate
2-5mins
Learning OutcomesCheat Sheet
Paper art showing periodic table, electron shells, chemical test icons on teal background for Chemistry Unit 2 quiz

Ready to boost your confidence? Dive into our chemistry unit 2 test designed for students eager to master the periodic table, electron shells and essential chemical tests. This chemistry test unit 2 lets you challenge your understanding while enjoying a dynamic chemistry unit 2 practice test format. Whether you're prepping for a chem unit 2 review session or gearing up for the big chemistry unit 2 exam, you'll sharpen your skills and identify areas needing extra focus. Explore interactive sections like a periodic table quiz and a chemistry practice quiz to supercharge your study plan. Take on the challenge now and see how far you can go!

What does the atomic number of an element represent?
The total number of protons and neutrons
The number of protons in the nucleus
The mass of the most common isotope
The number of electrons in any atom of the element
The atomic number is defined as the number of protons in an atom's nucleus. In a neutral atom, this also equals the number of electrons. This fundamental definition differentiates each element. For more details see Chemguide: Atomic Number.
What is the maximum number of electrons that can occupy the second electron shell (n=2)?
32
8
18
2
The second shell (n=2) has one 2s orbital (2 electrons) and three 2p orbitals (6 electrons), totaling 8 electrons. This follows the 2n^2 rule. Refer to Chemguide: Electron Shells.
Which group in the periodic table contains the alkali metals?
Group 17
Group 2
Group 18
Group 1
Alkali metals are found in Group 1 and include lithium, sodium, and potassium. They all have a single electron in their outer shell, giving them similar reactivity. More details at RSC: Group 1 Elements.
Which of the following is a noble gas?
Chlorine
Nitrogen
Fluorine
Neon
Neon is a noble gas located in Group 18 of the periodic table. Noble gases have full outer electron shells, making them largely unreactive. For more information see BBC Bitesize: Noble Gases.
What is the electron configuration of a sodium atom in its ground state?
1s2 2s2 2p6 3s1
1s2 2s2 2p6 3s2
1s2 2s2 2p6 3p1
1s2 2s2 2p5 3s2
Sodium has 11 electrons: two in 1s, two in 2s, six in 2p, and one in 3s, so the correct configuration is 1s2 2s2 2p6 3s1. This is detailed at Chemguide: Electron Configuration.
Which color flame does lithium produce during a flame test?
Green
Yellow
Red
Orange
Lithium salts give a crimson or red flame in a flame test due to electronic transitions in the Li+ ion. Other alkali metals give different colors. See RSC: Lithium Flame Test.
What ion is formed when calcium becomes a stable ion?
Ca3+
Ca -
Ca2+
Ca+
Calcium loses two electrons to achieve the stable electronic configuration of argon, forming Ca2+. This is typical for Group 2 elements. More at BBC Bitesize: Group 2 Elements.
What is the correct order of filling of the first four electron orbitals?
1s, 2p, 2s, 3s
1s, 2s, 2p, 3s
1s, 3s, 2s, 2p
2s, 1s, 2p, 3s
Orbitals fill in order of increasing energy: 1s, then 2s, then 2p, then 3s. This is a consequence of the Aufbau principle. See Chemguide: Orbital Filling.
How does atomic radius change across a period from left to right?
It increases
It decreases
It first increases then decreases
It remains constant
Across a period, nuclear charge increases without additional shielding, pulling electrons closer and decreasing atomic radius. This trend is well-documented. More at LibreTexts: Periodic Trends.
How does first ionization energy change down a group?
It remains unchanged
It increases
It increases then decreases
It decreases
Down a group, atomic size increases and shielding rises, making it easier to remove an electron, so the first ionization energy decreases. Details at Chemguide: Ionisation Energy.
Which reagent is commonly used to test for sulfate ions in solution?
Sodium hydroxide
Silver nitrate
Barium chloride
Hydrochloric acid
Barium chloride reacts with sulfate ions to form a white precipitate of barium sulfate. This is a standard qualitative test for sulfates. See Chemguide: Sulfate Test.
What is the result of adding a dilute acid to a carbonate compound?
No visible reaction
Blue precipitate forms
Effervescence of carbon dioxide
Formation of ammonia gas
Dilute acids react with carbonates to release CO2 gas, causing effervescence. This test is often used to identify carbonates. More at BBC Bitesize: Carbonates.
Which test would confirm the presence of ammonium ions?
Warm with sodium hydroxide, damp red litmus turns blue
Add silver nitrate, white precipitate forms
Perform a flame test, red flame appears
Add barium chloride, white precipitate forms
Ammonium ions react with warm NaOH to release ammonia gas, which turns damp red litmus blue. This is a classical test for NH4+. See Chemguide: Ammonium Test.
Why does reactivity increase down Group 2 metals?
Atomic radius decreases
Number of protons decreases
Outer electrons are further from the nucleus
Nuclear charge decreases down the group
As you move down Group 2, atoms get larger and the outer electrons experience more shielding, making them easier to remove. This increases reactivity. More at BBC Bitesize: Group 2 Reactivity.
The graph of first ionization energies across Period 3 shows a drop from magnesium to aluminum. What explains this drop?
An electron is removed from a higher-energy 3p subshell in aluminum
The nuclear charge decreases in aluminum
Shielding by inner electrons is lower in aluminum
Electron-electron repulsion is reduced in aluminum
Aluminum's outer electron is in the 3p subshell, which is higher in energy and further from the nucleus than magnesium's 3s electron, making it easier to remove. This causes the ionization energy drop. See Chemguide: Periodicity in Ionisation.
Which electron configuration shows an exception to the Aufbau principle?
Sc: [Ar] 3d1 4s2
Zn: [Ar] 3d10 4s2
Cr: [Ar] 3d5 4s1
Fe: [Ar] 3d6 4s2
Chromium has a half-filled 3d subshell ([Ar] 3d5 4s1) rather than the expected 3d4 4s2 because half-filled subshells have extra stability. Details at Chemguide: Subshell Exceptions.
Which statement best explains electron affinity?
The energy required to remove an electron from a neutral atom
The energy change when a neutral atom gains an electron
The energy change when a neutral atom loses a proton
The energy released when a proton is added to the nucleus
Electron affinity refers to the energy change when an atom in the gas phase gains an electron to form an anion. It quantifies how easily an atom accepts an electron. More at LibreTexts: Electron Affinity.
In a halide test using silver nitrate, a cream precipitate indicates which ion?
Iodide ions
Bromide ions
Fluoride ions
Chloride ions
Silver nitrate reacts with bromide ions to form a cream-colored silver bromide precipitate. Chloride gives white, iodide gives yellow. See Chemguide: Halide Tests.
What color precipitate forms when lead(II) nitrate reacts with iodide ions?
White
Cream
Red
Yellow
Lead(II) iodide is a yellow precipitate formed when iodide ions react with lead(II) nitrate. This characteristic color is used in qualitative analysis. More at Chemguide: Iodide Test.
Which species has the smallest ionic radius?
Mg2+
F?
Na+
O2?
Among those ions, Na+ has the smallest radius because it has lost an entire electron shell and has a high effective nuclear charge relative to the number of electrons. See LibreTexts: Ionic Radii.
Which Group 1 metal has the highest melting point?
Potassium
Lithium
Sodium
Rubidium
Lithium has the highest melting point among the alkali metals because its small cation leads to a stronger metallic lattice. Reactivity increases and melting point decreases down the group. More at RSC: Lithium Properties.
What is the correct half-equation for the reduction of copper(II) ions to copper metal?
Cu2+ ? Cu+ + e?
Cu ? Cu2+ + 2e?
Cu2+ + e? ? Cu+
Cu2+ + 2e? ? Cu
Reduction involves gain of electrons. Copper(II) ions gain two electrons to form copper metal: Cu2+ + 2e? ? Cu. See Chemguide: Half-Equations.
Which factor contributes most to the high lattice energy of magnesium oxide compared to sodium chloride?
Higher charge density of Mg2+ and O2?
Lower charge on Na+ and Cl?
Higher covalent character in NaCl
Larger ionic radii of Mg2+ and O2?
Lattice energy is greatest for ions with high charges and small radii, so Mg2+ and O2? have a much higher charge density and produce a stronger ionic bond than Na+ and Cl?. See LibreTexts: Born - Haber Cycles.
In molecular orbital theory, what is the bond order of O??
3
2
2.5
1
O? has 8 bonding and 4 antibonding electrons: bond order = (8?4)/2 = 2. A bond order of 2 corresponds to a double bond. More at Chemguide: MO Theory.
Which qualitative test can distinguish propanone (acetone) from propanal (an aldehyde)?
Bromine water decolorizes only propanone
Tollens' reagent gives a silver mirror with propanal only
Acidified dichromate oxidizes only propanone
Fehling's solution gives red precipitate with propanone
Propanal is an aldehyde and reduces Tollens' reagent to metallic silver, forming a silver mirror, whereas propanone (a ketone) does not react. See Chemguide: Tollens' Test.
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Study Outcomes

  1. Understand Periodic Table Organization -

    Identify element groups, periods, and key trends in atomic properties to navigate the periodic table effectively.

  2. Analyze Periodic Trends -

    Compare atomic radius, ionization energy, and electronegativity patterns to predict element behavior and reactivity.

  3. Apply Electron Shell Configuration Rules -

    Write and interpret electron configurations using the Aufbau principle, Pauli exclusion principle, and Hund's rule for main-group elements.

  4. Interpret Chemical Test Methods -

    Recognize common qualitative tests for gases and ions - such as flame tests, gas evolution, and precipitation reactions - to identify unknown substances.

  5. Evaluate Reaction Outcomes -

    Assess test results and balanced chemical equations to determine the presence of specific ions or compounds in sample analyses.

Cheat Sheet

  1. Periodic Table Structure & Trends -

    According to IUPAC guidelines, elements are arranged by increasing atomic number into periods and groups, which reveal trends in atomic radius, electronegativity and ionisation energy. In your chemistry unit 2 practice test, remember that atomic radius decreases across a period and increases down a group. Use the mnemonic "ADI" (Across Decreases, Down Increases) to lock in this trend before the exam.

  2. Electron Shell Configurations & Aufbau Principle -

    Building on the shell model from UC Berkeley's Chemistry department, electrons fill orbitals in order of increasing energy (1s→2s→2p…), following the Aufbau principle, Hund's rule and the Pauli exclusion principle. For example, sodium in your chem unit 2 review appears as 1s2 2s2 2p6 3s1, often memorised as 2 8 1. Chanting the sequence "1s2, 2s2, 2p6, 3s1" aloud helps cement orbital order under exam pressure.

  3. Ionisation Energy & Effective Nuclear Charge -

    As described by the Royal Society of Chemistry, effective nuclear charge (Z_eff) increases across a period, pulling electrons closer and raising ionisation energy. In a chemistry unit 2 exam question, watch for anomalies at Be→B and N→O due to subshell electron repulsion. Practice calculating Z_eff using Z_eff = Z − S (where S is shielding electrons) to strengthen trend interpretation skills.

  4. Flame Tests for Cation Identification -

    According to CLEAPSS and RSC resources, flame tests rapidly identify metal cations by their emission colours - sodium yields bright yellow, potassium lilac, and calcium brick-red. In your chemistry unit 2 practice test, use a clean platinum or nichrome wire dipped in dilute HCl between samples to prevent contamination. A handy phrase is "Na Yellow, K Lilac, Ca Red Brick" to recall Na, K and Ca flame colours.

  5. Precipitation Reactions for Anion Testing -

    Official exam boards like AQA and Edexcel list key tests: chloride with AgNO3 yields a white precipitate, bromide gives cream and iodide yellow, while sulphate forms a white precipitate with BaCl2 in acidic conditions. During your chem unit 2 review, ensure you can write full ionic equations - e.g., Ag+ + Cl− → AgCl(s). Practising these reactions in the context of a chemistry test unit 2 scenario boosts speed and accuracy under timed conditions.

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