Covalent and Ionic Bonds Overview

Covalent Bond Details

• A coordinate bond (also called a dative covalent bond) is a type of covalent bond
• In a coordinate bond, one atom donates both electrons to the bond
• Atoms donate a lone pair of electrons to another atom needing electrons
• Examples include ammonia (where nitrogen donates a lone pair)
• Coordinate bonds are often found in coordination compounds
• These compounds have a central metal ion surrounded by ligands
• Coordinate bonds generally have a higher bond length compared to standard covalent bonds
• Coordinate bonds can be considered as Lewis acid-base reactions: a Lewis base is an electron donor and a Lewis acid is an electron acceptor
• Examples of compounds containing coordinate bonds include O3, SO3, and H2SO4

Ionic Bond Formation

• An ionic bond forms when one or more electrons are transferred between atoms
• This transfer results in the formation of ions with opposite charges
• Metals lose electrons to become positively charged ions (cations)
• Nonmetals gain electrons to become negatively charged ions (anions)
• Oppositely charged ions attract each other, forming the ionic bond
• Example 1: Sodium Chloride (NaCl)
  • Sodium (Na) loses one electron to become Na+
  • Chlorine (Cl) gains one electron to become Cl-
  • Na+ and Cl- ions attract, forming an ionic bond
• Example 2: Calcium Oxide (CaO)
  • Calcium (Ca) loses two electrons to become Ca2+
• Ionic bonds are formed by the electrostatic attraction between oppositely charged ions.

Electronic Theory of Valence

• The electronic theory of valence was proposed by Kossel and Lewis in 1916
• They proposed a logical explanation of valence based on the inertness of noble gases
• Octet rule: atoms achieve stability by having 8 electrons in their outermost shell (octet)
• During bond formation, atoms lose, gain or share electrons to achieve a stable octet configuration

Occurrence of Metal

• Metals can be found in nature in both free and combined states
• Free state: metals like gold, silver, and platinum exist in their elemental forms. Metals that are less reactive or noble are in free state.
• Combined state: most metals are reactive and exist in combined states, often as compounds in minerals and ores

Metallurgy

• Metallurgy is a process for extracting metals from their ores
• Basic concepts include:
  • Minerals: naturally occurring inorganic compounds
  • Ores: minerals containing a metal that can be extracted economically
  • Gangue: impurities present in the ore
  • Flux: a substance used to remove impurities
  • Slag: waste material produced during extraction
  • Alloys: mixtures of two or more metals
• Stages of metallurgy include concentration, extraction, and refining

Chemical Processes (Calcination and Roasting)

• Calcination: Heating the ore in the absence, or limited supply of air
  • Removing moisture or other volatile materials
  • Decomposing ores Example: Heating Calcium Carbonate (CaCO3) to Calcium Oxide (CaO) and releasing Carbon Dioxide gas (CO2)
  • Type of Ore: Calcium Carbonate
• Roasting: Heating the ore in the presence of air
  • Converting the metal compounds into oxides, often in the presence of air.
  • Usually for sulphide ores. Removing sulphur impurities. Example: Heating a sulphide ore to produce an oxide

Electro-Magnetic Separation

• Electro-magnetic separation is a method for separating magnetic and non magnetic materials
• Non-magnetic materials are separated from magnetic materials.
• The magnetic materials are attracted to the magnetic field.

Gravity Separation

• Gravity separation is a method for separating components in mixture based on their/specific densities
• The method utilizes the difference in specific gravities
• Heavier components sink to the bottom and lighter components rise to the top

Names of Ores and Formulas

• Several ores and their corresponding chemical formulas are listed.