Elements, Compounds, and Mixtures in Organic Chemistry

Matter is categorized into two primary divisions: Pure Substances and Mixtures.
Pure Substances are further divided into:
- Elements
  - Metals
  - Nonmetals
  - Metalloids
- Compounds
  - Organic Compounds
  - Inorganic Compounds, which include Ionic and Covalent types.
Mixtures are classified based on their uniformity:
- Homogeneous Mixtures
  - Solutions
- Heterogeneous Mixtures
  - Colloids
  - Suspensions

Elements
- Elements are fundamental or elementary substances that cannot be broken down into simpler substances by chemical means.
- When the subatomic particles of an element are separated from its atom, it no longer retains the properties of that element.
- Examples of elements include:
  - Hydrogen ( $H$ )
  - Carbon ( $C$ )
  - Oxygen
  - Aluminum
  - $\text{ion (Fe)}$
Compounds
- A compound is a distinct substance that contains two or more elements combined in a definite proportion by weight.
- Compounds can only be separated by chemical means.
- Examples of compounds include:
  - Water ( $H_2O$ )
  - Carbon dioxide ( $CO_2$ )
  - Acetone ( $C_3H_{6}0$ or $CH_3COCH_3$ )
  - Glucose ( $C_6H_{12}O_6$ )
  - Sodium bicarbonate ( $NaHCO_3$ )
  - Sodium chloride ( $NaCl$ )
  - Hydrogen peroxide ( $H_2O_2$ )

General Properties of Mixtures
- Mixtures can be separated by physical means.
Heterogeneous Mixtures
- Suspensions: Examples include iron sludge and quicksand.
- Emulsions: Examples include oil/water mixtures and milk.
- Solid Sols: Examples include iron ore, granite, liquid concrete mayonnaise, and marble.
Homogeneous Mixtures
- Gas Mixtures: Examples include protective gas and air.
- Solutions: Examples include sugar water, carbonated soda, schnapps, and superheated steam.
- Aerosols: Examples include cigarette smoke, water spray, and car exhaust.
- Alloys: Examples include brass, bronze, and solder.

A metal alloy is a solid solution created by combining metals or combining one or more metals with non-metallic elements.
Key metal alloy compositions:
- $gold + copper = red\,gold$
- $gold + silver = white\,gold$
- $silver + copper = sterling\,silver$
- $iron + carbon = steel$
- $copper + tin = bronze$
- $copper + zinc = brass$

Chemical Composition
- Organic compounds are primarily made up of carbon atoms bonded to hydrogen atoms.
- Other essential elements found in organic compounds include oxygen and nitrogen.
- Minor constituent elements include sulfur, phosphorus, and halogens such as fluorine, chlorine, bromine, and iodine.
Biochemical Significance
- The chemicals in living systems are almost entirely organic compounds, including:
  - Carbohydrates
  - Lipids
  - Proteins
  - Enzymes
  - Nucleic acids
  - Hormones
  - Vitamins
Statistical Prevalence
- Chemists have discovered or synthesized over $10 \times 10^6$ organic compounds.
- Approximately $100,000$ new organic compounds are discovered or made each year.
- In contrast, there are an estimated $1.7 \times 10^6$ inorganic compounds.
- Organic compounds constitute approximately $85\%$ of all known compounds.

Historically, scientists supported the Vital Force Theory, which posited that a "vital force" inherent in living organisms was necessary to produce organic compounds.
Under this theory, organic compounds could only be formed by other organic processes.
The demise of the Vital Force Theory began with an experiment performed by Wöhler in $1828$ , the first in a series that proved organic compounds could be synthesized from inorganic materials.
Wöhler's Synthesis Reaction:
- $NH_4Cl + AgNCO \xrightarrow{heat} H_2N-C-NH_2 + AgCl$
- Reactants: Ammonium chloride ( $NH_4Cl$ ) and Silver cyanate ( $AgNCO$ ).
- Products: Urea ( $H_2N-C-NH_2$ ) and Silver chloride ( $AgCl$ ).

Structural Formula: Represents the atoms present in a molecule and the specific bonds connecting them.
VSEPR Model (Valence Shell Electron Pair Repulsion): Used to predict molecular geometry and bond angles. Common angles in organic chemistry include $109.5^\circ$ , $120^\circ$ , and $180^\circ$ .
Examples of Molecular Geometry and Angles:
- Ethane: Bond angles are $109.5^\circ$ .
- Ethylene: Bond angles are $120^\circ$ .
- Acetylene: Bond angles are $180^\circ$ .
- Chloroethane: Bond angles are $109.5^\circ$ .
- Methanol: Bond angles are $109.5^\circ$ .
- Formaldehyde: Bond angles are $120^\circ$ .
- Methanamine: Bond angles are $109.5^\circ$ .
- Methyleneimine: Bond angles are $120^\circ$ .

Organic Compounds
- Bonding: Bonding is almost entirely covalent.
- Physical State: May exist as gases, liquids, or solids with low melting points (typically less than $360^\circ C$ ).
- Solubility: Most are insoluble in water but soluble in organic solvents like diethyl ether, toluene, and dichloromethane.
- Conductivity: Aqueous solutions do not conduct electricity.
- Combustibility: Almost all organic compounds burn.
- Reaction Speed: Chemical reactions are usually slow.
Inorganic Compounds
- Bonding: Most possess ionic bonds.
- Physical State: Most are solids characterized by high melting points.
- Solubility: Many are soluble in water but almost all are insoluble in organic solvents.
- Conductivity: Aqueous solutions conduct electricity.
- Combustibility: Very few inorganic compounds burn.
- Reaction Speed: Chemical reactions are often very fast.

Institution: Emilio Aguinaldo College (Cavite), specifically associated with BIOCHEM 1st SEM 2024-25.
Institutional Motto: Virtue, Excellence, Service.
Personnel Reference: Ellen Mercado.
Document Codes: QF-PQM-051 (03.07.2024) Rev.0, OF-POM-051 (03.07.2024), QF-PQM-051 (03.07.2024) Rev.03.