Atomic Models and Chemical Bonding: A Comprehensive View
Atomic Models
Dalton Model
- Each element is composed of indivisible particles called atoms.
- In an element, all the atoms are identical.
- Atoms of different elements are all different.
- When atoms of more than one element combine, they form molecules. Compounds are made of molecules.
- In a chemical reaction, atoms are not created, destroyed, or changed into other types of atoms.
Thomson Model
Thomson based this model on his work with cathode rays. In this model, an atom consists of a positively charged jellylike
Read MoreCrude Oil, Hydrocarbons, and Chemical Processes
Crude Oil and Fractional Distillation
Crude oil is a complex mixture of hydrocarbons (compounds containing hydrogen and carbon only). Crude oil is separated by fractional distillation in a continuous process, taking off the samples at different levels from the fractionating column. The dissolved gases come out of the top, and the boiling points rise as one goes down the column.
- Refinery gases: Used for bottled gases such as gas, propane, butane
- Gasoline: Fuel for cars (petrol)
- Kerosene: Fuel for jet
Alkali, Alkaline Earth, Aluminum, Halogen, Oxygen, and Sulfur Properties
Element Representation
Alkali and Alkaline Earth Metals
Alkali and alkaline earth metals have low ionization potential (IP) and electron affinity (EA), meaning they easily lose electrons. They have increasing atomic radius (Z) down a column, higher density, and lower melting points.
Physical Properties: Good conductors of heat and electricity, low melting points, and are soft.
Chemical Properties: They are strong reducing agents, readily forming ionic compounds. They react with oxygen to form oxides
Read MoreUnderstanding Chemical Bonds: Types and Properties
Chemical Bonds: Types and Properties
In chemical bonds, atoms tend to bind to each other to form more complex entities, which make up substances.
Ionic Bonds
When an atom that is missing a few electrons in its valence shell is faced with another atom of low electronegativity, an electron transfer occurs. This is common between metals and nonmetals. The fundamental process of electron transfer results in what is known as an ionic network or crystal. In ionic compounds, we cannot speak of individual
Read MoreCovalent Bonds and Molecular Structures: Key Concepts
Covalent Bonds and Molecular Structures
Types of Covalent Bonds
- Non-polar Covalent Bonds: Electronegativity difference is close to zero (less than 0.4).
- London Dispersion Force: Weak attraction between nonpolar molecules; the more electrons, the greater the attraction.
- Polar Covalent Bonds: Electronegativity difference is between 0.4 and 1.67. The higher the difference, the more polar the bond.
Dipole Moment
A dipole moment (polar molecule) is a molecule that has a center of positive charge and a center
Read MoreAldol Condensation: Reactions, Mechanisms, and Types
Aldol condensation is a condensation reaction in organic chemistry in which an enol or an enolate ion reacts with a carbonyl compound to form a β-hydroxyaldehyde or β-hydroxyketone, followed by dehydration to give a conjugated enone. Aldol condensations are important in organic synthesis because they provide a good way to form carbon-carbon bonds. For example, the Robinson annulation reaction sequence features an aldol condensation; the Wieland-Miescher ketone product is an important starting
Read More