Lesson · S.3.1
Basic atomic structure
Protons, neutrons, and electrons, plus how the periodic table encodes an element's identity, explained the way the TEAS tests it.
ObjectiveS.3.1Read2 minExam weightChemistry ≈ 18% of Science
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See editions and pricing →What you will be able to do
- Identify the charge, location, and role of protons, neutrons, and electrons.
- Calculate an atom's atomic number and mass number from its particle counts.
- Explain how isotopes and ions differ from a neutral atom.
What the lesson concludes
- Atomic number equals the number of protons and defines the element.
- Mass number equals protons plus neutrons.
- Isotopes are atoms of one element with different neutron counts.
- A neutral atom has equal protons and electrons; an unequal count makes it an ion.
- Elements in the same periodic table group share outer electron counts and similar reactivity.