Notes, summaries, assignments, exams, and problems for Chemistry

Evolution of Atomic Models: Limitations and Contributions

Limitations of Early Atomic Models

Dalton's Atomic Theory: Unexplained Phenomena

• Cathode and Positive Rays Behavior

  1. Cathode ray deflections in the presence of magnetic and electrical fields.
  2. The constancy of the quotient q/m in the particles that constitute cathode rays.

• Existence of Isotopes

  The concept of an element was changed according to Rutherford's model, which Dalton's theory did not account for.

Rutherford's Atomic Model: Theoretical Instability

• Atoms are theoretically unstable systems according to the laws of electromagnetism.
• This model could not explain atomic spectra.

Bohr's Atomic Model: Incomplete Explanations

• It could not explain the spectra of poly-electronic atoms.
• It did not fully

Main Group Elements: Characteristics and Applications

Group 3 Elements (Boron to Thallium)

The elements in Group 3 (Boron, Aluminum, Gallium, Indium, Thallium) share the electron configuration ns²p¹.

Properties of Boron and Aluminum

• Boron (B): A hard, brittle solid with poor electrical conductivity. It primarily forms covalent bonds, such as B-B.
• Aluminum (Al): A shiny, malleable, and ductile metal with good electrical conductivity. Its common oxidation number is +3.

Chemical Reactions and Characteristics

• Boron reacts with Chlorine at high temperatures to form boron trichloride.
• Aluminum burns vigorously when heated in oxygen:

  2Al + 3O2 → 2Al2O3

• Aluminum forms a self-protective layer of aluminum oxide (Al₂O₃) on its surface, which prevents further

Homologous Series

A series of organic compounds having similar structures and similar chemical properties in which the successive members differ in their molecular formula by -CH₂ group.

The different members of the series are called homologous.

Characteristics of Homologous Series

All the member of a homologous series can be described by a common general formula.

Example: All alkane can be described by the general formula C_nH_2n+2.

Each member of a homologous series differ from its higher and lower neighbouring members by a common difference of -CH₂ group.

Cations and Anions

Naming Monatomic Anions

                               Respiratory

1. A processes that take place in the cell to convert energy from nutrients into ATP, and them release waste

2. Carbon dioxide

3. A.)Nose B.)Pharynx C.)Carynx  D.)Trachea E.) Lung F.) Bronchioles G.) Alvelos

4. From the nose inhale oxygen then goes through the trachea then to the bronchus the goes through brochioles then to the alveoli that exchange with cappilaries  oxygen takes back carbon dioxide to exhale it .

5. In the alveoli it exchanges with cuppilaries.

Alveoli gives oxygen and cappilaries diffues carbon dioxide .

6. (I) Inhale oxygen

  (II) Exhale carbon dioxide

Enthalpy, Rate Equations, and Halogens

Enthalpy Change of Solution

The enthalpy change that accompanies the dissolving of 1 mole of gaseous ions in H₂O to form 1 mol of aqueous ions is -1008/2 = -504 kJ mol^-1. F^- has a more exothermic hydration enthalpy as it has a smaller ionic radius, leading to a stronger attraction to H₂O molecules. The bond enthalpy for F-F is +158 kJ mol^-1.

Rate Equations and Reaction Mechanisms

For the reaction: Fe³⁺ + 2I^- --> FeI₂⁺, the rate equation is: rate = k[Fe³⁺][I^-]², where k = 22.5 dm⁶mol^-2s^-1. The mechanism for this reaction is a two-step process:

1. Fe³⁺ + 2I^- --> FeI₂⁺
2. Fe³⁺ + FeI₂⁺ --> 2Fe²⁺ + I₂

Halogens

Halogens have more electrons, leading to stronger London forces between molecules. This means more heat... Continue reading "A Level Chemistry Notes: Enthalpy, Kinetics, and Equilibrium" »

Polyatomic Ions

• PO₄^-3 = Phosphate
• NO₃^-1 = Nitrate
• NO₂^-1 = Nitrite
• CrO₄^-2 = Chromate
• SO₄^-2 = Sulfate
• CO₃^-2 = Carbonate
• SO₃^-2 = Sulfite
• MnO₄^-1 = Permanganate
• HCO₃^-1 = Bicarbonate
• CH₃CO₂^-1 = Acetate
• ClO₄^-1 = Perchlorate
• ClO₃^-1 = Chlorate
• OH^-1 = Hydroxide
• CN^-1 = Cyanide
• NH₄⁺¹ = Ammonium

Naming Mineral Acids

• HF = Hydrofluoric Acid
• HCl = Hydrochloric Acid
• HBr = Hydrobromic Acid
• HI = Hydroiodic Acid

Naming Oxacids

• HNO₂ = Nitrous Acid
• H₂SO₃ = Sulfurous Acid

Diatomic

• N₂, O₂, F₂, Cl₂, Br₂, I₂

Metric Conversions

• Giga^9
• Mega^6
• Kilo^3
• Base = 1
• Deci^-1
• Centi^-2
• Milli^-3
• Micro^-6
• Nano^-9
• Pico^-12

Atomic Models

• Bohr: Based on the assumption that electrons travel in specific shells around the nucleus. Did not work for systems with more than 1 electron.
• Rutherford: Theorized that atoms have their

Scientific Method

Ask a question.

Research.

Make a hypothesis.

Experiment and test your hypothesis.

Analyze your test results.

Present a conclusion.

Chemistry

Chemistry is the branch of science that studies the properties of matter and how matter interacts with energy.

Organic Chemistry

The branch of chemistry concerned with the study of compounds that contain the element carbon.

Inorganic Chemistry

The branch of chemistry concerned with the study of materials that contain any combination of chemical elements.

Element

A substance that cannot be broken into two or more simpler substances by any physical or chemical method and made of the same kind of atoms.

Compound

A molecule of a pure substance that contains two or more elements combined.

Heterogeneous Mixture

A... Continue reading "Scientific Method and Chemistry: An Introduction to Matter and Atoms" »

Halogenation

Halogenation: The reaction of an alkane with a halogen (X2 = F, Cl, Br, I) occurs when a mixture of the two is irradiated with ultraviolet light.

Combustion

Combustion: The reaction of an alkane with O2 occurs during combustion when the alkane is used as a fuel. Carbon dioxide and water are formed as products, and a large amount of heat is released.

An example of a combustion reaction:

CH4 + 2 O2 → CO2 + 2 H2O + Energy

Complete

Complete: C2H6 (g) + O2 (g) → CO2 (g) + H2O (g) + Energy

Incomplete

Incomplete: C3H8 (g) + O2 (g) → H2O (g) + CO2 (g) + CO (g) + C (s) + Energy

Petroleum

Petroleum: Complex mixture of alkanes that can be separated into fractions by distillation. Separating molecules based on differences in boiling points is called... Continue reading "Halogenation, Combustion, Complete and Incomplete Reactions, Petroleum, Refining, Alkenes" »