Atomic Structure Basics Quiz

Grade 7 · Science · Quiz

Test your understanding of atomic particles, atomic number, mass number, and how atoms are organized on the periodic table.

Questions

1. An element has atomic number 8. What is the element?

   1. Carbon
   2. Nitrogen
   3. Oxygen
   4. Sulfur
   Show answer

   Answer: Oxygen

   Oxygen has atomic number 8, meaning every oxygen atom has exactly 8 protons. The periodic table lists elements in order of atomic number.

2. Which subatomic particle has the least mass?

   1. Proton
   2. Neutron
   3. Electron
   4. They all have equal mass
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   Answer: Electron

   Electrons are about 1,836 times lighter than protons or neutrons. Their mass is so small it is often considered negligible when calculating atomic mass.

3. An atom has 11 protons and 12 neutrons. What is its mass number?

   1. 11
   2. 12
   3. 23
   4. 1
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   Answer: 23

   Mass number = protons + neutrons = 11 + 12 = 23. This atom is sodium-23, the most common form of sodium.

4. Two atoms can be isotopes of the same element if they have the same number of protons but different numbers of neutrons.

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   Answer: True

   Isotopes are atoms of the same element (same proton count) with different neutron counts. For example, carbon-12 and carbon-14 are both carbon isotopes.

5. Where are electrons located in an atom?

   1. Inside the nucleus
   2. In energy levels outside the nucleus
   3. Mixed throughout the nucleus
   4. Only on the surface of the nucleus
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   Answer: In energy levels outside the nucleus

   Electrons occupy energy levels (also called shells or orbitals) in the space surrounding the nucleus. They are not inside the nucleus.

6. An atom gains 2 electrons. What does it become?

   1. A neutral atom
   2. A positively charged ion
   3. A negatively charged ion
   4. An isotope
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   Answer: A negatively charged ion

   Gaining electrons adds negative charges to a neutral atom, making it a negatively charged ion (anion). Losing electrons creates a positively charged ion (cation).

7. The number of protons in the nucleus of an atom is called its ______ number.

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   Answer: atomic

   The atomic number uniquely identifies each element. It equals the number of protons and determines where the element appears on the periodic table.

8. Which statement best describes the nucleus of an atom?

   1. It is large and diffuse, taking up most of the atom's volume
   2. It contains only electrons
   3. It is small, dense, and contains protons and neutrons
   4. It has a negative charge because of electrons
   Show answer

   Answer: It is small, dense, and contains protons and neutrons

   The nucleus is extremely small — about 100,000 times smaller than the whole atom — but contains nearly all of the atom's mass. It holds protons (+) and neutrons (neutral).

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