What are the impurities in 22 carat gold?

 22-carat gold contains 91.67% pure gold and 8.33% other metals (often called alloys) added intentionally to provide strength and durability. 

These added metals—which are not considered impurities but deliberate mixtures—typically include: 

• Copper
• Silver
• Zinc
• Nickel (occasionally) 

Because pure gold (24-carat) is too soft and malleable to hold its shape or bear the weight of daily wear, these non-gold metals are essential for making it suitable for jewelry crafting

Electrons in metals behave like a gas or a liquid

 Electrons in metals behave more like a liquid than an independent gas. While early theories treated them as a simple bouncing "gas," strong electrical repulsions mean they actually flow as a correlated fluid called a Fermi liquid. [1, 2, 3, 4]

The Electron Gas Model

The classical Drude-Sommerfeld model treats conduction electrons as a "free electron gas". [1, 2]

• How it works: Electrons move randomly in all directions, much like molecules in an ideal gas, but they do not bounce off one another.
• What it explains: It successfully predicts basic electrical and thermal conductivity, as well as the heat capacity of metals.
• Why it falls short: It ignores the fact that electrons are highly charged and repel each other. [1, 2, 3, 4, 5]

The Electron Liquid Model (Fermi Liquid Theory)

Because the concentration of electrons in a metal is incredibly high (roughly \(10^{29} \text{ per m}^3\)), they are constantly interacting via Coulomb forces. This requires a quantum fluid approach. [1, 2, 3, 4, 5]

• How it works: Electrons drag and coordinate with one another. Instead of moving independently, they flow collectively as a highly viscous, charged liquid. [1, 2, 3]
• What it explains: It accurately describes complex phenomena like superconductivity, specific types of resistance, and how electrons "screen" or hide the charge of impurities

What are the types of chemical bonds?

 Chemical bonds hold atoms together to form molecules and compounds. The three primary types of strong bonds are ionic, covalent, and metallic, while hydrogen bonds and London dispersion forces act as weaker, temporary connections. [1, 2]

1. Primary (Strong) Bonds

• Ionic Bonds: Formed when electrons are completely transferred from one atom to another, creating positive and negative ions that attract each other.
  • Mechanism: Electrostatic attraction.
  • Example: Sodium chloride (table salt), where \(Na^{+}\) and \(Cl^{-}\) attract. [1, 2, 3]
• Covalent Bonds: Formed when atoms share pairs of electrons to achieve stability. These can be nonpolar (electrons shared equally) or polar (electrons shared unequally).
  • Mechanism: Shared electron orbits.
  • Example: Water (\(H_{2}O\)), carbon dioxide (\(CO_{2}\)). [1, 2, 3, 4]
• Metallic Bonds: Occur between metal atoms where electrons are free to move across a lattice structure in a "sea of electrons".
  • Mechanism: Delocalized electrons.
  • Example: Pure metals like copper, iron, or gold. [1, 2, 3, 4]

2. Secondary (Weak) Bonds

• Hydrogen Bonds: Weak electrostatic attractions occurring when a hydrogen atom covalently bound to a highly electronegative atom is attracted to another electronegative atom.
  • Example: Bonds between water molecules. [1, 2]
• Van der Waals Forces / London Dispersion: Weak, temporary attractions caused by shifting electron densities in atoms or molecules.

what are polar and non polar molecules?

 Polar molecules have an unequal sharing of electrons, creating partial positive and negative charges (a "net dipole"). Nonpolar molecules share electrons equally or have symmetrical shapes that perfectly cancel out any charge differences. This key difference determines how substances dissolve, mix, and react. 

Common Polar Molecules

These molecules feature asymmetrical shapes or lone pairs of electrons that cause an uneven pull. [1, 2]

• Water (\(H_{2}O\))
• Ammonia (\(NH_{3}\))
• Hydrogen Fluoride (\(HF\))
• Sulfur Dioxide (\(SO_{2}\))
• Hydrogen Chloride (\(HCl\))
• Ethanol (\(C_{2}H_{5}OH\))
• Carbon Monoxide (\(CO\))
• Acetone (\(CH_{3}COCH_{3}\)) 

Common Non-Polar Molecules

These molecules typically have a symmetrical geometry, causing the pulls of individual atoms to cancel each other out.

• Oxygen Gas (\(O_{2}\))
• Carbon Dioxide (\(CO_{2}\))
• Methane (\(CH_{4}\))
• Nitrogen Gas (\(N_{2}\))
• Benzene (\(C_{6}H_{6}\))
• Carbon Tetrachloride (\(CCl_{4}\))
• Hexane (\(C_{6}H_{14}\))
• Hydrogen Gas (\(H_{2}\)) 

Key Differences

Feature	Polar Molecules	Nonpolar Molecules
Electron Sharing	Unequal (electrons spend more time near the more electronegative atom).	Equal (electrons are shared evenly across the atoms).
Symmetry	Asymmetrical.	Symmetrical.
Charge	Has distinct positive and negative ends (poles).	No distinct positive or negative ends.
Common Examples	Water (\(H_{2}O\)), Ammonia (\(NH_{3}\)), Hydrochloric Acid (\(HCl\)).	Carbon Dioxide (\(CO_{2}\)), Methane (\(CH_{4}\)), Oxygen gas (\(O_{2}\)).