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Quizzes > Science

First 20 Elements Quiz: From Hydrogen to Calcium

Quick, free practice for the periodic table 1-20. Instant results.

Editorial: Review CompletedCreated By: Alcoholic OminousUpdated Aug 23, 2025
Difficulty: Moderate
2-5mins
Learning OutcomesCheat Sheet
Paper art periodic table quiz first 20 elements on dark blue background with paper cut letters and atomic symbols.

Use this quiz to recall and name the first 20 elements of the periodic table, from hydrogen to calcium. Answer quickly, spot gaps before a test, and see your score instantly. For extra practice, warm up with elements 1 to 10, try a broader periodic table elements quiz, or build speed with periodic table practice.

Which element has atomic number 1?
Nitrogen
Helium
Oxygen
Hydrogen
Hydrogen has atomic number 1 because it contains one proton in its nucleus. It is the lightest and most abundant element in the universe and serves as the foundation for chemistry. Hydrogen is classified as a nonmetal and appears at the top of group 1 in the periodic table.
What is the chemical symbol for oxygen?
O
Om
Og
Ox
The chemical symbol for oxygen is O, derived from the first letter of its name. Oxygen is a diatomic molecule (O2) at standard conditions and is essential for most forms of life. It is positioned at atomic number 8 in the periodic table.
Which of the following is a noble gas?
Neon
Carbon
Oxygen
Nitrogen
Neon is a noble gas in group 18 of the periodic table, characterized by its full valence shell and low chemical reactivity. It is atomic number 10 and is used in lighting and signage. Noble gases have stable electron configurations, making them inert under standard conditions.
Which of the following is a halogen?
Neon
Sulfur
Sodium
Fluorine
Fluorine is a halogen in group 17 of the periodic table, known for being the most electronegative element. It has atomic number 9 and forms compounds such as HF and fluorides. Halogens typically exist as diatomic molecules and are highly reactive nonmetals.
What is the chemical symbol for sodium?
N
So
Na
S
The symbol Na comes from the Latin name 'natrium' and represents the element sodium, atomic number 11. Sodium is a highly reactive alkali metal that reacts vigorously with water. It is essential for biological functions such as nerve impulses and electrolyte balance.
Which of the following is an alkali metal?
Beryllium
Carbon
Boron
Lithium
Lithium is an alkali metal in group 1 of the periodic table and has atomic number 3. Alkali metals are soft, highly reactive, and have a single electron in their outer shell. Lithium is used in batteries and has a low density compared to other metals.
Which element is most abundant in Earth's crust?
Oxygen
Silicon
Iron
Aluminum
Oxygen makes up about 46% of Earth's crust by weight and is predominantly found in oxides and silicates. It has atomic number 8 and is the most abundant element in the crust. Silicon is the second most abundant at about 28%.
Which element has the symbol Mg?
Molybdenum
Mercury
Magnesium
Manganese
Mg is the symbol for magnesium, atomic number 12, an alkaline earth metal in group 2. Magnesium is lightweight and used in alloys for aerospace applications. It burns with a bright white flame when ignited.
What is the atomic number of calcium?
19
18
20
21
Calcium has atomic number 20, meaning it has 20 protons in its nucleus. It is an alkaline earth metal in group 2 and is essential for biological processes like bone formation. Calcium compounds such as calcium carbonate are common in rocks and shells.
Which element among the first 20 has the highest electronegativity?
Nitrogen
Chlorine
Fluorine
Oxygen
Fluorine is the most electronegative element with a Pauling value of 3.98, attracting electrons more strongly than any other element. It is highly reactive, especially with hydrogen. Electronegativity decreases down a group and increases across a period.
What is the electron configuration of neon in standard notation?
1s2 2s2 2p6
1s2 2p6 2s2
1s2 2s2 2p5
1s2 2s1 2p6
Neon has the electron configuration 1s2 2s2 2p6, filling both the 2s and 2p subshells. This full valence shell makes it chemically inert as a noble gas. The configuration reflects a complete second energy level.
Which element has an atomic mass closest to 32 amu?
Chlorine
Potassium
Sulfur
Phosphorus
Sulfur has an atomic mass of approximately 32.06 amu, making it the closest to 32 on the periodic table. It is a nonmetal in group 16 and forms compounds such as SO2 and H2S. Sulfur's common isotopes are S-32, S-33, S-34, and S-36.
Which element has three valence electrons?
Aluminum
Oxygen
Nitrogen
Carbon
Aluminum has three valence electrons in the 3s and 3p orbitals, giving it a +3 oxidation state in many compounds. It is in group 13 of the periodic table. Valence electrons determine reactivity and bonding behavior.
Identify the metalloid among the first 20 elements.
Nitrogen
Boron
Carbon
Oxygen
Boron is classified as a metalloid due to its intermediate properties between metals and nonmetals. It is in group 13 and has atomic number 5. Boron is used in semiconductors and borosilicate glass.
Which of these is an alkaline earth metal?
Sodium
Aluminum
Magnesium
Silicon
Magnesium is an alkaline earth metal in group 2 with atomic number 12. It has two valence electrons and forms +2 cations in compounds such as MgO and MgCl2. These metals are harder and have higher melting points than alkali metals.
Which element has the electron configuration [Ne] 3s2 3p1?
Sodium
Silicon
Phosphorus
Aluminum
Aluminum has the ground-state electron configuration [Ne] 3s2 3p1, indicating it has three electrons beyond the neon core. This configuration places it in group 13. It commonly forms a +3 oxidation state.
Which of these elements has the largest atomic radius?
Chlorine
Potassium
Argon
Calcium
Atomic radius increases down a group and decreases across a period. Potassium, in period 4 group 1, has the largest radius among these choices. Argon is smaller because noble gases have compact electron shells.
Which element has the highest first ionization energy among the first 20 elements?
Helium
Oxygen
Fluorine
Neon
Helium has the highest first ionization energy because its two electrons are held very tightly in the 1s orbital. It is the smallest atom with a full shell and thus requires the most energy to remove an electron.
Which isotope has 12 protons and 13 neutrons?
Al-27
Mg-26
Mg-24
Mg-25
An isotope with 12 protons is magnesium (atomic number 12). If it has 13 neutrons, its mass number is 25, making it Mg-25. Mg-24 has 12 neutrons and Mg-26 has 14.
What is the oxidation state of nitrogen in ammonia (NH3)?
+1
+3
-1
-3
In NH3, hydrogen has an oxidation state of +1 each, totaling +3. To balance that, nitrogen must be -3. This gives the molecule a net charge of zero.
Which element has an atomic mass closest to 40 amu?
Argon
Calcium
Potassium
Sulfur
Argon's atomic mass is about 39.95 amu, which is closest to 40 among the first 20 elements. Calcium is slightly above at 40.08 amu, and potassium is 39.10 amu. Argon is a noble gas in period 3.
Which alkaline earth metal is in period 4?
Beryllium
Magnesium
Calcium
Strontium
Calcium is the alkaline earth metal in period 4 with atomic number 20. Magnesium (12) and beryllium (4) are in periods 3 and 2, respectively. Strontium (38) is in period 5.
Which element among the first 20 has the greatest number of stable isotopes?
Sulfur
Silicon
Magnesium
Calcium
Calcium has six stable isotopes (40, 42, 43, 44, 46, 48), the most of any element in the first 20. Magnesium has three, silicon has three, and sulfur has four. The variety of isotopes contributes to calcium's use in geochronology.
Which second-period element has the highest electron affinity?
Carbon
Oxygen
Fluorine
Nitrogen
Among second-period elements, fluorine has the highest electron affinity at about 328 kJ/mol. This high value reflects fluorine's strong tendency to gain an electron to achieve a full valence shell. Electron affinity generally increases across a period.
Which ion has the larger ionic radius?
Al3+
Na+
Mg2+
Ne
Among these, Na+ has the largest ionic radius because it has the smallest positive charge relative to its electron cloud size. Mg2+ and Al3+ have higher charges pulling the electrons closer. Neutral neon is a noble gas atom, but ionic radii comparisons consider charged species.
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Study Outcomes

  1. Identify Element Names and Symbols -

    Accurately match each of the first 20 elements of the periodic table with its chemical symbol in the quiz, improving your recall precision.

  2. Recall Atomic Numbers and Positions -

    Memorize and retrieve atomic numbers and their positions on the periodic table, strengthening your foundational understanding of element ordering.

  3. Classify Element Categories -

    Differentiate metals, nonmetals, and metalloids among the first twenty elements, enhancing your grasp of their chemical properties.

  4. Apply Quiz Strategies -

    Use targeted recall techniques and mnemonic devices during the periodic table quiz to improve speed and accuracy.

  5. Analyze Performance Feedback -

    Interpret quiz results to identify strengths and areas for improvement, guiding focused study on missing elements.

  6. Reinforce Long-Term Retention -

    Leverage repeated practice in the first 20 elements quiz to solidify your memory and boost confidence in chemistry fundamentals.

Cheat Sheet

  1. Essential Element Details -

    Start by memorizing each element's name, symbol, and atomic number for the first 20 elements of the periodic table quiz with flashcards or an app like Anki. A classic mnemonic - "Happy Henry Likes Beans Brown, Boring Cops Nauseate Or Foul Neighbors" (H, He, Li, Be, B, C, N, O, F, Ne) - can boost recall for the first ten. University of Texas Chemistry resources confirm that pairing symbols with atomic numbers forms the foundation for mastering elements 1 - 20.

  2. Group and Period Classification -

    Organize the first 20 elements into s-block (Groups 1 - 2) and p-block (Groups 13 - 18) categories to see patterns in reactivity and properties; for example, alkali metals (Li, Na, K) are highly reactive with water while noble gases (He, Ne, Ar) are inert. When tackling a periodic table quiz first 20 elements, recognizing these families helps predict behavior, such as Group 17 halogens forming salts with Group 1 metals. Purdue University's ChemCollective highlights that grouping simplifies learning trends across periods and down families.

  3. Electron Configuration Patterns -

    Apply the Aufbau principle to write configurations from hydrogen (1s¹) up to calcium ([Ar] 4s²), noting that periods 1 - 4 fill 1s, 2s/2p, 3s/3p, and 4s orbitals respectively. For carbon (atomic number 6), the configuration is 1s² 2s² 2p², and for sulfur (16) it's [Ne] 3s² 3p❴ - practice these to solidify orbital filling order. MIT OpenCourseWare emphasizes that knowing these builds a strong conceptual base for predicting chemical bonding and reactivity in this elements quiz.

  4. Key Periodic Trends -

    Recognize that atomic radius decreases left to right across a period due to increasing nuclear charge, while first ionization energy and electronegativity generally rise (for instance, Li→Ne). Plotting these values for elements 1 - 20 from NIST data shows clear, reproducible trends that can guide multiple-choice answers in the first twenty elements quiz. Mastering these trends is crucial for predicting which element in a set will have the lowest ionization energy or largest atomic size.

  5. Common Compounds and Valency Practice -

    Write formulas for everyday compounds - H₂O, NaCl, CO₂, MgO, and CaCO₃ - by matching element valencies (e.g., O²❻ with Mg²❺ gives MgO). Practicing these simple compounds reinforces the concept of oxidation states and formula writing, a frequent challenge in elements quiz 1-20 sections. The Royal Society of Chemistry validates that hands-on formula exercises sharpen your ability to predict chemical formulas under exam conditions.

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