This checkpoint covers the atomic-structure and model-development block: subatomic particles, atomic number, mass number, isotopes and model change through evidence.
This checkpoint tests the second block of the unit, where atom structure becomes more detailed and model change becomes evidence-based.
Subatomic particles, charge, location, atomic number, mass number and neutral atoms.
Isotopes as same element, different neutron number, with simple uses.
Dalton, Thomson, Rutherford and Bohr plus usefulness and limits of models.
Strong answers use evidence-based reasoning, not memorised names alone.
1. Which particle is negatively charged?
2. What does atomic number count?
3. What is mass number?
4. Two atoms have the same proton number but different neutron numbers. What are they?
5. Why are isotopes still the same element?
6. Why did atomic models change over time?
7. Which scientist is linked most strongly to the nuclear model in this unit?
8. Why can a simplified classroom model still be useful?
9. A neutral atom has 9 protons. How many electrons does it have?
10. Which statement is strongest?
Explain the difference between atomic number and mass number.
Explain why two atoms can be isotopes of the same element.
Explain why a simplified atomic model can still be useful in a science classroom.
1: C. Electrons are negatively charged.
2: A. Atomic number counts protons.
3: D. Mass number is protons plus neutrons.
4: B. They are isotopes.
5: A. Same proton number means same element.
6: C. New evidence supported better explanations.
7: D. Rutherford is linked strongly to the nuclear model.
8: B. It can still be useful if it shows the main structure clearly.
9: A. A neutral atom has equal protons and electrons.
10: C. That statement best captures the block.
Atomic number is the number of protons, while mass number is the number of protons plus neutrons. They are different counts and should not be confused.
Two atoms can be isotopes of the same element because they have the same proton number but different neutron numbers. This keeps the element identity the same while changing the mass number.
A simplified model can still be useful because it helps communicate the main structure clearly. It does not need to be a perfect copy of reality to support learning.
Subatomic particles and atom numbers must stay clearly separated.
Same element means same proton number.
Evidence is the reason models changed over time.
Next block applies this understanding to the periodic table.