객관식
Which of the following best describes an element?
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- 1. Intro to General Chemistry3h 46m
- Classification of Matter18m
- Physical & Chemical Changes19m
- Chemical Properties7m
- Physical Properties5m
- Intensive vs. Extensive Properties13m
- Temperature12m
- Scientific Notation13m
- SI Units7m
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- Significant Figures9m
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- Conversion Factors16m
- Dimensional Analysis17m
- Density12m
- Density of Geometric Objects19m
- Density of Non-Geometric Objects5m
- 2. Atoms & Elements4h 17m
- The Atom9m
- Subatomic Particles15m
- Isotopes17m
- Ions27m
- Atomic Mass28m
- Periodic Table: Classifications11m
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- Calculating Molar Mass10m
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- Millikan Oil Drop Experiment7m
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- Combustion Analysis38m
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- Polyatomic Ions24m
- Naming Ionic Compounds11m
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- Naming Acids18m
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- Functional Groups in Chemistry11m
- 4. BONUS: Lab Techniques and Procedures1h 25m
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- 9. Quantum Mechanics2h 59m
- Wavelength and Frequency6m
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- Introduction to Quantum Mechanics5m
- Quantum Numbers: Principal Quantum Number5m
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- 10. Periodic Properties of the Elements3h 10m
- The Electron Configuration22m
- The Electron Configuration: Condensed4m
- The Electron Configurations: Exceptions13m
- The Electron Configuration: Ions12m
- Paramagnetism and Diamagnetism8m
- The Electron Configuration: Quantum Numbers16m
- Valence Electrons of Elements12m
- Periodic Trend: Metallic Character3m
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- 11. Bonding & Molecular Structure3h 29m
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- 12. Molecular Shapes & Valence Bond Theory1h 58m
- 13. Liquids, Solids & Intermolecular Forces2h 24m
- Molecular Polarity10m
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- 15. Chemical Kinetics2h 53m
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- 17. Acid and Base Equilibrium5h 5m
- Acids Introduction9m
- Bases Introduction7m
- Binary Acids15m
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- Bases14m
- Amphoteric Species5m
- Arrhenius Acids and Bases5m
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- Diprotic Acids and Bases8m
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- Triprotic Acids and Bases10m
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- 18. Aqueous Equilibrium4h 47m
- Intro to Buffers20m
- Henderson-Hasselbalch Equation19m
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- Strong Titrate-Strong Titrant Curves9m
- Weak Titrate-Strong Titrant Curves15m
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- Titrations: Weak Acid-Strong Base38m
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- Titrations: Diprotic & Polyprotic Buffers32m
- Solubility Product Constant: Ksp17m
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- 19. Chemical Thermodynamics1h 51m
- 20. Electrochemistry2h 42m
- 21. Nuclear Chemistry2h 37m
- Intro to Radioactivity10m
- Alpha Decay9m
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- Measuring Radioactivity7m
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- Mass Defect19m
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- 22. Organic Chemistry5h 7m
- Introduction to Organic Chemistry8m
- Structural Formula8m
- Condensed Formula10m
- Skeletal Formula6m
- Spatial Orientation of Bonds3m
- Intro to Hydrocarbons16m
- Isomers11m
- Chirality15m
- Functional Groups in Chemistry11m
- Naming Alkanes4m
- The Alkyl Groups9m
- Naming Alkanes with Substituents13m
- Naming Cyclic Alkanes6m
- Naming Other Substituents8m
- Naming Alcohols11m
- Naming Alkenes11m
- Naming Alkynes9m
- Naming Ketones5m
- Naming Aldehydes5m
- Naming Carboxylic Acids4m
- Naming Esters8m
- Naming Ethers5m
- Naming Amines5m
- Naming Benzene7m
- Alkane Reactions7m
- Intro to Addition Reactions4m
- Halogenation Reactions4m
- Hydrogenation Reactions3m
- Hydrohalogenation Reactions7m
- Alcohol Reactions: Substitution Reactions4m
- Alcohol Reactions: Dehydration Reactions9m
- Intro to Redox Reactions8m
- Alcohol Reactions: Oxidation Reactions7m
- Aldehydes and Ketones Reactions6m
- Ester Reactions: Esterification4m
- Ester Reactions: Saponification3m
- Carboxylic Acid Reactions4m
- Amine Reactions3m
- Amide Formation4m
- Benzene Reactions10m
- 23. Chemistry of the Nonmetals2h 39m
- Main Group Elements: Bonding Types4m
- Main Group Elements: Boiling & Melting Points7m
- Main Group Elements: Density11m
- Main Group Elements: Periodic Trends7m
- The Electron Configuration Review16m
- Periodic Table Charges Review20m
- Hydrogen Isotopes4m
- Hydrogen Compounds11m
- Production of Hydrogen8m
- Group 1A and 2A Reactions7m
- Boron Family Reactions7m
- Boron Family: Borane7m
- Borane Reactions7m
- Nitrogen Family Reactions12m
- Oxides, Peroxides, and Superoxides12m
- Oxide Reactions4m
- Peroxide and Superoxide Reactions6m
- Noble Gas Compounds3m
- 24. Transition Metals and Coordination Compounds3h 19m
- Atomic Radius & Density of Transition Metals11m
- Electron Configurations of Transition Metals7m
- Electron Configurations of Transition Metals: Exceptions11m
- Paramagnetism and Diamagnetism10m
- Ligands10m
- Complex Ions5m
- Coordination Complexes7m
- Classification of Ligands11m
- Coordination Numbers & Geometry9m
- Naming Coordination Compounds22m
- Writing Formulas of Coordination Compounds8m
- Isomerism in Coordination Complexes17m
- Orientations of D Orbitals4m
- Intro to Crystal Field Theory10m
- Crystal Field Theory: Octahedral Complexes5m
- Crystal Field Theory: Tetrahedral Complexes4m
- Crystal Field Theory: Square Planar Complexes4m
- Crystal Field Theory Summary8m
- Magnetic Properties of Complex Ions9m
- Strong-Field vs Weak-Field Ligands6m
- Magnetic Properties of Complex Ions: Octahedral Complexes11m
2. Atoms & Elements
The Atom
Multiple Choice
Which gas makes up approximately 21% of Earth's atmosphere?
A
Nitrogen
B
Carbon dioxide
C
Oxygen
D
Argon
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검증된 단계별 안내1
Understand that Earth's atmosphere is composed of several gases, each with a specific percentage by volume.
Recall the major components of the atmosphere: Nitrogen (~78%), Oxygen (~21%), Argon (~0.93%), and Carbon dioxide (~0.04%).
Identify that the question asks for the gas that makes up approximately 21% of the atmosphere.
Match the given options with their typical atmospheric percentages: Nitrogen (~78%), Oxygen (~21%), Carbon dioxide (trace amounts), Argon (~0.93%).
Conclude that Oxygen is the gas that constitutes about 21% of Earth's atmosphere.
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