Science · Atoms and particles
Several numbers can describe the same atom, yet they answer different questions. Atomic number identifies an element by its proton count. Mass number counts protons and neutrons together. Electrical neutrality concerns the balance of positive and negative charge. Before calculating, write which of these questions the prompt actually asks.
The examples keep the particle counts explicit. You do not need a table of every element or a model of the electron’s path to solve them. Use a simple list headed protons, neutrons and electrons, then mark the entries needed for the requested number or comparison.
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Atomic number is the number of protons. Changing that count changes the element being identified. The number of neutrons or electrons is not a substitute for the proton count when the question asks for atomic number. Keep the definition beside your particle list.
Mass number combines the proton and neutron counts. In the stated example, six protons and eight neutrons give 6 + 8 = 14. This is a particle count named mass number, rather than a measurement of an atom’s mass in grams.
A proton has a positive charge and an electron a negative charge of equal magnitude. Equal counts balance in an electrically neutral atom. The question asks you to compare those two counts, rather than add every particle in the list.
Use the same list to review all three examples. Circle only protons for atomic number, protons plus neutrons for mass number, and the proton/electron comparison for neutrality. Explain why the unmarked entry is not used in each case. This checks the selection of information before the arithmetic and prevents one familiar number from becoming an answer to every atomic question.
TRY & READ
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Example 1 · Chemistry: atoms and the periodic table
Answer: Protons
Changing the proton number changes the element.
Basic facts and equations in this chapter concerning matter, atoms, reactions, or equilibrium. The questions, choices, and explanations were independently authored.
Source checked: 2026-10-03Example 2 · Chemistry: atoms and the periodic table
Answer: 14
Mass number is the sum of protons and neutrons: 6 + 8 = 14.
Basic facts and equations in this chapter concerning matter, atoms, reactions, or equilibrium. The questions, choices, and explanations were independently authored.
Source checked: 2026-10-03Example 3 · Chemistry: atoms and the periodic table
Answer: They are equal
Equal amounts of positive and negative charge balance.
Basic facts and equations in this chapter concerning matter, atoms, reactions, or equilibrium. The questions, choices, and explanations were independently authored.
Source checked: 2026-10-03Source checked: 2026-10-04
Topics: Chemistry: atoms and the periodic table. Range: Broader knowledge. Difficulty: Basic, Standard. These are selected initially. You can change these on the setup screen.
Try this topic in a quizA test shows explanations after submission. Continuous challenge explains each answer. Review uses unresolved mistakes recorded on this device. Casual mode does not update learning records.