1. States of Matter. The Atom and the Periodic Table
1.6. Electron Configurations
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The periodic table
Middle of the 19th century: Some 60 elements discovered.
- Mendeleev organizes them by atomic mass.
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The order in the periodic table
Atoms are ordered by atomic number.
The electrons in the atoms are ordered in electron shells, so they have the lowest possible energy.
- The closer to the nucleus, the lower the energy.
Models of some atoms
How many e– are there room for in the different shells?
Shell |
1 (K) |
2 (L) |
3 (M) |
4 (N) |
\(n\) |
Max. number of e– |
2 |
8 |
18 |
32 |
\(2n^2\) |
Electron configurations for some atoms
Element |
Atomic # |
K |
L |
M |
N |
Hydrogen, H |
1 |
1 |
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Helium, He |
2 |
2 |
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Litium, Li |
3 |
2 |
1 |
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Beryllium, Be |
4 |
2 |
2 |
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Fluorine, F |
9 |
2 |
7 |
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Neon, Ne |
10 |
2 |
8 |
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Sodium, Na |
11 |
2 |
8 |
1 |
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Sulfur, S |
16 |
2 |
8 |
6 |
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Argon, Ar |
18 |
2 |
8 |
8 |
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Potassium, K |
19 |
2 |
8 |
8 |
1 |
Zinc, Zn |
30 |
2 |
8 |
18 |
2 |
Krypton, Kr |
36 |
2 |
8 |
18 |
8 |
All the electrons marked in red are valence electrons.
ExampleGive the electron configuration for oxygen, 8O. SolutionOxygen has 8p+ and 8e–
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Valence electrons
Valence electrons decide much of an element's properties.
- These properties were what Mendeleev noticed!
- The farther away from the nucleus, the easier they may be released.
- The fewer they are, the easier they may be released.
- Eight valence electrons are particularly stable!
Rule of octets – noble gas configuration
- All the noble gases except helium have eight valence electrons.
- Eight valence electrons (or two, for helium) is called noble gas configuration.
- In chemical reactions: The atoms strive to attain noble gas configuration.
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Contents
- 1. States of Matter. The Atom and the Periodic Table
- 1.1. Matter. States of Matter
- 1.2. Elements and Chemical Compounds. Pure Substances and Mixtures
- 1.3. The Birth of Chemistry
- 1.4. Atomic Theory. The Atomic Model
- 1.5. Atomic Number, Mass Number, and Atomic Mass
- 1.6. Electron Configurations
- 1.7. Beyond Bohr's Atomic Model
- 1.8. Redox Reactions
- 1.9. The Structure of the Periodic Table
- 1.10. The Noble Gases
- 1.11. The Alkali Metals and the Halogens
- 1.12. The Alkaline Earth Metals and the Oxygen Group
- 1.13. A Few of the Elements in Group 13, 14, and 15
- 2. Chemical Calculations
- 2.1. Physical Quantity, Magnitude, and Units
- 2.2. Atomic Mass, Molecular Mass, and Unit Mass
- 2.3. Amount of Substance, Molar Mass, and Mass
- 2.4. Stoichiometry. The Mass is Preserved
- 2.5. Water of Crystallization
- 2.6. Calculating the Formula of a Chemical Compound
- 2.7. From Empirical to Molecular Formulas
- 2.8. Equivalent Amounts of Substance and Masses
- 2.9. Gases and Pressure
- 2.10. Concentrations
- 2.11. Dilutions
- 2.12. Yield
- 2.13. Limiting Reactants
- 3. Chemical Bonding
- 3.1. How Ionic Compounds are Formed
- 3.2. Precipitations
- 3.3. Names and Formulas of Ionic Compounds
- 3.4. Ionic Bonds
- 3.5. Properties of Ionic Compounds
- 3.6. Metal Bonding
- 3.7. Covalent Bonding
- 3.8. Polar Covalent Bonding
- 3.9. Dipoles. Polar and non-polar Molecules
- 3.10. The VSEPR Theory
- 3.11. Hydrogen Bonding. The Peculiar Water
- 3.12. Equals Solves Equal
- 3.13. Solubility of Gases in Water
- 3.14. Solubility of Salts in Water
- 4. Thermochemistry
- 5. Chemical Equilibrium
- 5.1. Reaction Rates
- 5.2. The Law of Mass Action
- 5.3. Calculations on Chemical Equilibrium
- 5.4. Heterogenous Equilibria. Solubility Product
- 5.5. Is the System at Equilibrium? The Reaction Quotient Q
- 5.6. Changing the Concentrations in a System in Equilibrium.
- 5.7. Diluting or Compressing Systems in Equilibrium, or Changing the Temperature
- 6. Acids and bases
- 7. Oxidation and Reduction
- 8. Electrochemistry
- 9. Organic Chemistry
- 9.1. Alkanes
- 9.2. Chain Isomers. Nomenclature
- 9.3. Haloalkanes
- 9.4. Nucleophilic Substitution
- 9.5. Alkenes
- 9.6. Electrophilic Addition. Markovnikov’s Rule
- 9.7. Elimination
- 9.8. Alkynes
- 9.9. Arenes and Aromatic Compounds
- 9.10. Alcohols
- 9.11. Oxidation of Alcohols
- 9.12. Aldehydes and Ketones
- 9.13. Thiols and Disulfides
- 9.14. Ethers
- 9.15. Amines
- 9.16. Nitro Compounds and Organic Nitrates
- 9.17. Carboxylic Acids
- 9.18. More on Carboxylic Acids
- 9.19. Stereoisomerism
- 9.20. Esters
- 9.21. Lipids
- 9.22. Mono-, Oligo-, and Polysaccharides
- 9.23. Amino Acids
- 9.24. Nucleotides
- 10. Biochemistry
- 10.1. Proteins
- 10.2. Enzymes
- 10.3. Catabolic Processes
- 10.4. Carrier Molecules
- 10.5. Glycolysis
- 10.6. Beta-oxidation
- 10.7. The Citric Acid Cycle
- 10.8. The Metabolism of Amino Acids
- 10.9. The Electron Transport Chain
- 10.10. Anabolic Processes
- 10.11. Gluconeogenesis and Fatty Acid Synthesis
- 10.12. DNA: Structure and Function
- 11. Analytical chemistry