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WGU D425 INTRODUCTION TO CHEMISTRY 2025/2026 –
COMPLETE PA & OA FINAL EXAM STUDY GUIDE WITH 230
VERIFIED QUESTIONS, DETAILED ANSWERS, AND
RATIONALES FOR EASY TEST PREP,100% CORRECT ALREADY
GRADED A+
Q1. Which subatomic particle has a negative charge and is found outside the
nucleus in orbitals?
A. Proton
B. Neutron
C. Electron
D. Positron
Answer: C. Electron
Rationale: Electrons are negatively charged particles located in orbitals
around the nucleus, responsible for bonding and chemical reactivity.
Q2. What is the atomic number of an element determined by?
A. Mass number
B. Number of neutrons
C. Number of protons
D. Number of isotopes
Answer: C. Number of protons
Rationale: The atomic number equals the number of protons in the nucleus,
which defines the identity of an element.
Q3. An isotope of carbon has 6 protons and 8 neutrons. What is its mass
number?
A. 6
B. 8
C. 14
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D. 12
Answer: C. 14
Rationale: Mass number = protons + neutrons = 6 + 8 = 14.
Q4. Which type of bond involves the complete transfer of electrons?
A. Covalent
B. Metallic
C. Hydrogen
D. Ionic
Answer: D. Ionic
Rationale: Ionic bonds form when electrons are transferred from one atom
to another, usually between metals and nonmetals.
Q5. The horizontal rows on the periodic table are called:
A. Groups
B. Families
C. Periods
D. Series
Answer: C. Periods
Rationale: Periods run left to right; groups run top to bottom. Period
number relates to energy levels of electrons.
Q6. Which element is a halogen?
A. Sodium
B. Oxygen
C. Chlorine
D. Magnesium
Answer: C. Chlorine
Rationale: Halogens belong to Group 17 and are highly reactive nonmetals.
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Q7. Which of the following is an alkaline earth metal?
A. Calcium
B. Fluorine
C. Sodium
D. Aluminum
Answer: A. Calcium
Rationale: Group 2 elements are alkaline earth metals, including calcium,
magnesium, and barium.
Q8. The molar mass of H₂O is approximately:
A. 10 g/mol
B. 14 g/mol
C. 18 g/mol
D. 20 g/mol
Answer: C. 18 g/mol
Rationale: H (1 × 2 = 2) + O (16) = 18 g/mol.
Q9. Which gas law states that pressure is inversely proportional to volume at
constant temperature?
A. Charles’ law
B. Avogadro’s law
C. Boyle’s law
D. Dalton’s law
Answer: C. Boyle’s law
Rationale: Boyle’s law: P₁V₁ = P₂V₂ at constant T.
Q10. What is the pH of a neutral solution at 25°C?
A. 0
B. 5
C. 7
D. 14
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Answer: C. 7
Rationale: Neutral solutions have equal H⁺ and OH⁻ ion concentrations,
giving pH = 7.
Q11. Which type of reaction is: 2H₂ + O₂ → 2H₂O?
A. Decomposition
B. Synthesis
C. Combustion
D. Double replacement
Answer: B. Synthesis
Rationale: Two reactants combine to form one product.
Q12. Which scientist proposed the planetary model of the atom?
A. Dalton
B. Rutherford
C. Bohr
D. Thomson
Answer: C. Bohr
Rationale: Niels Bohr described electrons orbiting the nucleus in fixed
energy levels.
Q13. Which type of radiation has the highest penetrating power?
A. Alpha
B. Beta
C. Gamma
D. Neutron
Answer: C. Gamma
Rationale: Gamma rays are high-energy electromagnetic waves that
penetrate deeply.
WGU D425 INTRODUCTION TO CHEMISTRY 2025/2026 –
COMPLETE PA & OA FINAL EXAM STUDY GUIDE WITH 230
VERIFIED QUESTIONS, DETAILED ANSWERS, AND
RATIONALES FOR EASY TEST PREP,100% CORRECT ALREADY
GRADED A+
Q1. Which subatomic particle has a negative charge and is found outside the
nucleus in orbitals?
A. Proton
B. Neutron
C. Electron
D. Positron
Answer: C. Electron
Rationale: Electrons are negatively charged particles located in orbitals
around the nucleus, responsible for bonding and chemical reactivity.
Q2. What is the atomic number of an element determined by?
A. Mass number
B. Number of neutrons
C. Number of protons
D. Number of isotopes
Answer: C. Number of protons
Rationale: The atomic number equals the number of protons in the nucleus,
which defines the identity of an element.
Q3. An isotope of carbon has 6 protons and 8 neutrons. What is its mass
number?
A. 6
B. 8
C. 14
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D. 12
Answer: C. 14
Rationale: Mass number = protons + neutrons = 6 + 8 = 14.
Q4. Which type of bond involves the complete transfer of electrons?
A. Covalent
B. Metallic
C. Hydrogen
D. Ionic
Answer: D. Ionic
Rationale: Ionic bonds form when electrons are transferred from one atom
to another, usually between metals and nonmetals.
Q5. The horizontal rows on the periodic table are called:
A. Groups
B. Families
C. Periods
D. Series
Answer: C. Periods
Rationale: Periods run left to right; groups run top to bottom. Period
number relates to energy levels of electrons.
Q6. Which element is a halogen?
A. Sodium
B. Oxygen
C. Chlorine
D. Magnesium
Answer: C. Chlorine
Rationale: Halogens belong to Group 17 and are highly reactive nonmetals.
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Q7. Which of the following is an alkaline earth metal?
A. Calcium
B. Fluorine
C. Sodium
D. Aluminum
Answer: A. Calcium
Rationale: Group 2 elements are alkaline earth metals, including calcium,
magnesium, and barium.
Q8. The molar mass of H₂O is approximately:
A. 10 g/mol
B. 14 g/mol
C. 18 g/mol
D. 20 g/mol
Answer: C. 18 g/mol
Rationale: H (1 × 2 = 2) + O (16) = 18 g/mol.
Q9. Which gas law states that pressure is inversely proportional to volume at
constant temperature?
A. Charles’ law
B. Avogadro’s law
C. Boyle’s law
D. Dalton’s law
Answer: C. Boyle’s law
Rationale: Boyle’s law: P₁V₁ = P₂V₂ at constant T.
Q10. What is the pH of a neutral solution at 25°C?
A. 0
B. 5
C. 7
D. 14
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Answer: C. 7
Rationale: Neutral solutions have equal H⁺ and OH⁻ ion concentrations,
giving pH = 7.
Q11. Which type of reaction is: 2H₂ + O₂ → 2H₂O?
A. Decomposition
B. Synthesis
C. Combustion
D. Double replacement
Answer: B. Synthesis
Rationale: Two reactants combine to form one product.
Q12. Which scientist proposed the planetary model of the atom?
A. Dalton
B. Rutherford
C. Bohr
D. Thomson
Answer: C. Bohr
Rationale: Niels Bohr described electrons orbiting the nucleus in fixed
energy levels.
Q13. Which type of radiation has the highest penetrating power?
A. Alpha
B. Beta
C. Gamma
D. Neutron
Answer: C. Gamma
Rationale: Gamma rays are high-energy electromagnetic waves that
penetrate deeply.
