Unit Checkpoint
Unit Summary
This checkpoint assesses your understanding of the entire Physical Science unit. Review the key concepts before attempting the assessment questions.
Topics Covered in This Unit
- Atomic Structure: protons, neutrons, electrons, and their arrangement
- The Periodic Table: organization, groups, periods, and trends
- Guided Practice: applying atomic concepts to problem-solving
- Lab Analysis: interpreting experimental data
- Claim-Evidence Writing: scientific argumentation using CER
Review Examples
Review these key examples before taking the checkpoint assessment.
Key Concept Review
Atomic Number vs Mass Number: Atomic number = number of protons (identifies element). Mass number = protons + neutrons.
Periodic Trends: Atomic radius decreases across a period; increases down a group. Electronegativity increases across a period.
Electron Configuration: Electrons fill lowest energy levels first. Valence electrons determine chemical properties.
✏️ Practice
Test your understanding with these practice questions.
Practice Questions
0/3 correctWhat is the scientific method's first step?
A hypothesis is:
Which is a property of matter?
Checkpoint Assessment
Complete these 10 questions to assess your mastery of the Physical Science unit.
Question 1: An atom has 17 protons, 18 neutrons, and 17 electrons. What element is it and what is its mass number?
Answer: The element is chlorine (Cl) because it has 17 protons. Mass number = 17 + 18 = 35, so this is chlorine-35.
Question 2: Why do elements in the same group have similar chemical properties?
Answer: Elements in the same group have the same number of valence electrons, which determines how they bond and react with other elements.
Question 3: What is the difference between an atom and an ion?
Answer: An atom has equal numbers of protons and electrons (neutral charge). An ion has gained or lost electrons, giving it a positive or negative charge.
Question 4: Explain the trend in atomic radius from sodium to argon.
Answer: Atomic radius decreases from Na to Ar because the number of protons increases (stronger nuclear pull on electrons) while electrons remain in the same energy level.
Question 5: A flame test produces a green color. What element might this be?
Answer: Copper (Cu) produces a green flame. Barium also produces a green color but is more yellow-green.
Question 6: How many valence electrons does sulfur have, and how did you determine this?
Answer: Sulfur has 6 valence electrons. It is in Group 16, and the group number minus 10 gives the number of valence electrons for elements in groups 13-18.
Question 7: What evidence would support the claim that potassium is more reactive than lithium?
Answer: Potassium reacts more vigorously with water than lithium, producing more heat and potentially igniting. K has a larger atomic radius, making its valence electron easier to remove.
Question 8: Explain why isotopes of the same element have identical chemical properties but different masses.
Answer: Isotopes have the same number of protons and electrons (same chemical behavior) but different numbers of neutrons (different mass).
Question 9: A sample has density 8.9 g/mL. Using the periodic table, what metal might this be?
Answer: This is likely copper (Cu), which has a density of approximately 8.96 g/mL.
Question 10: Write a claim about periodic trends and support it with evidence and reasoning.
Answer: Claim: Electronegativity increases across a period. Evidence: F has electronegativity 4.0, O has 3.5, N has 3.0, C has 2.5. Reasoning: As nuclear charge increases across a period, atoms more strongly attract bonding electrons.
Next Steps
- If you scored below 80%, review the lessons you found challenging
- Proceed to the next unit: Energy and Waves
- Use the SAT/ACT skills from this unit in future practice