WGU D425 CHEMISTRY OBJECTIVE ASSESSMENT EXAM| 300
PRACTICE QUESTIONS AND ANSWERS (VERIFIED ANSWERS) |
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1. Which statement best describes the relationship between an element's atomic number
and its identity?
A. It equals the number of neutrons in the nucleus
B. It equals the number of protons in the nucleus
C. It equals the number of protons plus neutrons
D. It equals the number of valence electrons
Answer: B
The atomic number is defined by the number of protons in an atom's nucleus. Changing the
number of protons changes the element itself.
2. A neutral atom contains 17 protons and 18 neutrons. Which notation correctly
represents this atom?
A. Chlorine-18
B. Argon-35
C. Chlorine-35
D. Sulfur-35
Answer: C
An atom with 17 protons is chlorine. Its mass number is 17 + 18 = 35, so the isotope is
chlorine-35.
3. Which subatomic particle has the smallest mass?
A. Proton
B. Neutron
C. Alpha particle
D. Electron
Answer: D
An electron has a mass of approximately 1/1836 that of a proton, making it far lighter than
either a proton or neutron.
,4. A student determines that an atom has 12 protons, 12 neutrons, and 10 electrons. What
is the charge of the particle?
A. 2+
B. 2−
C. Neutral
D. 22+
Answer: A
The particle has two more protons than electrons. Therefore, its net charge is 2+.
5. Which property is most directly associated with an element's position in the periodic
table?
A. The date it was discovered
B. The number of laboratory samples available
C. Its atomic number and electron configuration
D. Its physical state at room temperature only
Answer: C
The periodic table is organized by increasing atomic number, while an element's electron
configuration determines many of its chemical properties and periodic trends.
6. Which electron configuration represents a ground-state oxygen atom?
A. 1s²2s²2p⁴
B. 1s²2s²2p⁶
C. 1s²2s⁴2p²
D. 1s²2p⁶
Answer: A
Oxygen has eight electrons. Filling the orbitals according to the Aufbau principle gives
1s²2s²2p⁴.
7. An element is located in Group 1 of the periodic table. Which behavior is most
characteristic of the element?
A. It tends to gain two electrons
B. It tends to form a 1+ ion
C. It tends to form a 2− ion
D. It normally forms four covalent bonds
Answer: B
,Group 1 elements have one valence electron and commonly lose that electron to form 1+ ions.
8. Which trend generally occurs as atomic radius increases down a group?
A. Atomic radius decreases because nuclear charge disappears
B. Atomic radius remains constant
C. Atomic radius increases because additional electron shells are occupied
D. Atomic radius decreases because atoms lose all valence electrons
Answer: C
Atoms become larger down a group because additional occupied energy levels place the outer
electrons farther from the nucleus.
9. Which element has the greatest electronegativity?
A. Fluorine
B. Sodium
C. Magnesium
D. Potassium
Answer: A
Fluorine has the highest electronegativity of all elements because it strongly attracts shared
electrons.
10. A chemistry student compares sodium and chlorine. Which statement correctly
explains why chlorine has a smaller atomic radius?
A. Chlorine has fewer occupied energy levels
B. Chlorine has a greater effective nuclear charge within the same principal energy level
C. Chlorine has fewer protons
D. Chlorine has no valence electrons
Answer: B
Sodium and chlorine are in the same period, but chlorine has more protons while adding
electrons to the same principal energy level. The stronger effective nuclear attraction
produces a smaller radius.
11. Which type of bond results primarily from the electrostatic attraction between
oppositely charged ions?
A. Metallic
B. Hydrogen
, C. Ionic
D. Nonpolar covalent
Answer: C
Ionic bonding occurs when oppositely charged ions attract each other, typically following
electron transfer between a metal and a nonmetal.
12. Which compound is most likely to contain an ionic bond?
A. CO₂
B. CH₄
C. NaCl
D. O₂
Answer: C
Sodium is a metal and chlorine is a nonmetal. Sodium transfers an electron to chlorine,
producing Na⁺ and Cl⁻ ions held together by ionic attraction.
13. What is the correct formula for the compound formed between Mg²⁺ and Cl⁻?
A. MgCl
B. MgCl₂
C. Mg₂Cl
D. Mg₂Cl₂
Answer: B
Two chloride ions are required to balance the +2 charge of one magnesium ion, producing
MgCl₂.
14. Which molecule contains a nonpolar covalent bond?
A. HCl
B. HF
C. Cl₂
D. H₂O
Answer: C
Two identical chlorine atoms have equal electronegativities and therefore share electrons
equally, creating a nonpolar covalent bond.
15. A laboratory technician dissolves potassium nitrate in water. Which interaction
primarily allows the ionic compound to dissolve?
PRACTICE QUESTIONS AND ANSWERS (VERIFIED ANSWERS) |
EXAM PREP PRACTICE QUESTIONS AND ANSWERS | LATEST
EXAM GUIDE 2026&2027
1. Which statement best describes the relationship between an element's atomic number
and its identity?
A. It equals the number of neutrons in the nucleus
B. It equals the number of protons in the nucleus
C. It equals the number of protons plus neutrons
D. It equals the number of valence electrons
Answer: B
The atomic number is defined by the number of protons in an atom's nucleus. Changing the
number of protons changes the element itself.
2. A neutral atom contains 17 protons and 18 neutrons. Which notation correctly
represents this atom?
A. Chlorine-18
B. Argon-35
C. Chlorine-35
D. Sulfur-35
Answer: C
An atom with 17 protons is chlorine. Its mass number is 17 + 18 = 35, so the isotope is
chlorine-35.
3. Which subatomic particle has the smallest mass?
A. Proton
B. Neutron
C. Alpha particle
D. Electron
Answer: D
An electron has a mass of approximately 1/1836 that of a proton, making it far lighter than
either a proton or neutron.
,4. A student determines that an atom has 12 protons, 12 neutrons, and 10 electrons. What
is the charge of the particle?
A. 2+
B. 2−
C. Neutral
D. 22+
Answer: A
The particle has two more protons than electrons. Therefore, its net charge is 2+.
5. Which property is most directly associated with an element's position in the periodic
table?
A. The date it was discovered
B. The number of laboratory samples available
C. Its atomic number and electron configuration
D. Its physical state at room temperature only
Answer: C
The periodic table is organized by increasing atomic number, while an element's electron
configuration determines many of its chemical properties and periodic trends.
6. Which electron configuration represents a ground-state oxygen atom?
A. 1s²2s²2p⁴
B. 1s²2s²2p⁶
C. 1s²2s⁴2p²
D. 1s²2p⁶
Answer: A
Oxygen has eight electrons. Filling the orbitals according to the Aufbau principle gives
1s²2s²2p⁴.
7. An element is located in Group 1 of the periodic table. Which behavior is most
characteristic of the element?
A. It tends to gain two electrons
B. It tends to form a 1+ ion
C. It tends to form a 2− ion
D. It normally forms four covalent bonds
Answer: B
,Group 1 elements have one valence electron and commonly lose that electron to form 1+ ions.
8. Which trend generally occurs as atomic radius increases down a group?
A. Atomic radius decreases because nuclear charge disappears
B. Atomic radius remains constant
C. Atomic radius increases because additional electron shells are occupied
D. Atomic radius decreases because atoms lose all valence electrons
Answer: C
Atoms become larger down a group because additional occupied energy levels place the outer
electrons farther from the nucleus.
9. Which element has the greatest electronegativity?
A. Fluorine
B. Sodium
C. Magnesium
D. Potassium
Answer: A
Fluorine has the highest electronegativity of all elements because it strongly attracts shared
electrons.
10. A chemistry student compares sodium and chlorine. Which statement correctly
explains why chlorine has a smaller atomic radius?
A. Chlorine has fewer occupied energy levels
B. Chlorine has a greater effective nuclear charge within the same principal energy level
C. Chlorine has fewer protons
D. Chlorine has no valence electrons
Answer: B
Sodium and chlorine are in the same period, but chlorine has more protons while adding
electrons to the same principal energy level. The stronger effective nuclear attraction
produces a smaller radius.
11. Which type of bond results primarily from the electrostatic attraction between
oppositely charged ions?
A. Metallic
B. Hydrogen
, C. Ionic
D. Nonpolar covalent
Answer: C
Ionic bonding occurs when oppositely charged ions attract each other, typically following
electron transfer between a metal and a nonmetal.
12. Which compound is most likely to contain an ionic bond?
A. CO₂
B. CH₄
C. NaCl
D. O₂
Answer: C
Sodium is a metal and chlorine is a nonmetal. Sodium transfers an electron to chlorine,
producing Na⁺ and Cl⁻ ions held together by ionic attraction.
13. What is the correct formula for the compound formed between Mg²⁺ and Cl⁻?
A. MgCl
B. MgCl₂
C. Mg₂Cl
D. Mg₂Cl₂
Answer: B
Two chloride ions are required to balance the +2 charge of one magnesium ion, producing
MgCl₂.
14. Which molecule contains a nonpolar covalent bond?
A. HCl
B. HF
C. Cl₂
D. H₂O
Answer: C
Two identical chlorine atoms have equal electronegativities and therefore share electrons
equally, creating a nonpolar covalent bond.
15. A laboratory technician dissolves potassium nitrate in water. Which interaction
primarily allows the ionic compound to dissolve?
