Atomic Structure and Separation Processes

Atomic Structure and Models

• Atom: The smallest unit of a substance that cannot be broken down further
• Element: A substance containing only one type of atom, not breakable down.
• Compound: Formed when two or more elements chemically combine
• Mixture: Two or more elements not chemically combined.
• Isotope: A different version of the same element, has a different number of neutrons.
• Number of electrons = number of protons in a neutral atom
• Atomic model: Models have evolved with discoveries (e.g., electrons orbiting nucleus)
• Plum pudding model: Positive mass with evenly distributed negative electrons
• Nuclear model: Empty space with concentrated positive nucleus and orbiting electrons. The scattering experiment showed the concentrated nucleus.
• Relative charge on a neutral atom is 0 because the number of protons equals the number of electrons.

Separation Processes

• Filtration: Separates solids from liquids or gases.
• Crystallization: Separates solid crystals from a solution by evaporating the solvent.
• Simple Distillation: Separates a solvent from a solution (e.g., pure water from seawater).
• Fractional Distillation: Separates mixtures of liquids with different boiling points (e.g., crude oil).
• Chromatography: Separates mixtures of soluble substances.

Periodic Table

• Periodic table: Organized by atomic number (increasing number of protons).
• Groups: Columns with similar properties. Elements in a group have the same number of electrons in their outer shells.
• Development: Initially arranged by atomic weight; later by atomic number after the discovery of protons, electrons, and neutrons; Mendeleev left gaps for undiscovered elements.
• Isotopes impacted the understanding of the arrangement of elements in the table.

Reactivity of Groups

• Metals form positive ions; non-metals form negative ions.
• Group 0 (Noble gases): Unreactive due to stable electron configurations. Boiling points increase down the group.
• Group 1 (Alkali metals): One electron in the outer shell. Increasing reactivity down the group (weaker attraction to the nucleus).
• Group 7 (Halogens): Seven electrons in the outer shell. Decreasing reactivity down the group (weaker attraction to the nucleus). Halogens form salts when they react.

Transition Metals

• Transition metals are useful as catalysts.
• They have similar properties such as similar melting and boiling points.
• Mostly solid (except Mercury), malleable, and high density.

Bonding

• Ionic bonding: Metal + nonmetal. Transfer of electrons, creating positive metal ions and negative non-metal ions. Strong electrostatic forces between these ions. Results in a lattice structure and high melting/boiling points.
• Covalent bonding: Nonmetal + nonmetal. Sharing of electrons. Forms molecules and smaller substances or giant structures such as diamond, which have high melting/boiling points.
• Metallic bonding: Metal + metal. Delocalized electrons shared throughout the structure, strong bonds, high melting/boiling points, malleability/ductility.

Particle Model

• Stronger forces mean higher melting/boiling points (more energy required to break the forces).
• Simple particle models have limitations like not showing forces between particles. Solid, Liquid and gas states are explained in terms of particle arrangement and speed of particles.
• Ionic compounds have high melting/boiling points due to the strong electrostatic forces in the giant ionic lattice structure.
• Conduct electricity when molten or dissolved in water as ions can move freely.
• Gases and Liquids have low melting/boiling points due to weaker intermolecular forces. Intermolecular forces increase in size with increased molecular size. The size of intermolecular forces determine whether materials are solids, liquid or gases.

Polymers

• Polymers: Held together by strong covalent bonds within the polymer chain.
• Strong intermolecular forces result in them being solids at room temperature.

Metals

• Metals: Good electrical conductors due to delocalized electrons allowing charge movement.
• Pure metals are soft and malleable due to their layered structure; mixtures with other metals form alloys to make them harder.

Carbon Structures

• Diamond: Very hard, high melting point, does not conduct electricity (strong covalent bonds in a tetrahedral structure).
• Graphite: Conducts electricity due to delocalised electrons; structured in layers, low melting point due to weak intermolecular forces.

Earth and Air

• Earth's atmosphere: Primarily nitrogen (80%), oxygen (20%), small amounts of other gases.
• Theory of atmosphere's formation: Volcanic eruptions released gases; oceans formed, absorbing CO2; photosynthesis increased oxygen. CO2 is absorbed through the seas.
• Oxygen levels increased over time allowing animals to evolve.

Human Activities and Greenhouse Gases

• Human activities increase CO2 and other greenhouse gases (e.g., methane) through industries and agriculture.
• Combustion reactions with insufficient oxygen produce carbon monoxide and soot.

Crude Oil and Polymers

• Crude oil: Formed from dead plankton buried in the mud. Hydrocarbons (alkanes: CnH2n+2)
• Fractional distillation separates crude oil into different fractions based on boiling points.
• Cracking: Breaking down long-chain hydrocarbons into shorter, more useful hydrocarbons, typically to produce alkanes and alkenes. This is done through catalytic cracking (using a catalyst) and steam cracking.
• Saturated hydrocarbons (alkanes) turn into unsaturated hydrocarbons(alkenes) during cracking.
• Alkenes have a double bond in the middle C=C.
• Alkenes (CnH2n) are detected by their ability to decolorize bromine water from brown to colorless
• Combustion of hydrocarbons produces energy. Complete combustion produces CO2 and H2O. Incomplete combustion produces CO, C, or unburnt hydrocarbons.

Reactions of Alkenes, Alkanes

• Alkenes react via addition reactions with other compounds. Examples include addition reactions with hydrogen(alkene to alkane), water(alkene to alcohol), or halogens(alkene to haloalkane).
• The combustion of alkanes produces carbon dioxide and water.

Energy

• Exothermic reactions transfer heat to the surroundings.
• Endothermic reactions absorb heat from the surroundings.
• Activation energy: The minimum energy needed for a reaction to occur.

Reaction Rates

• Factors affecting reaction rate: Concentration, pressure, surface area, temperature, catalysts.
• Collision theory: More collisions, faster reaction rate.
• Equilibrium: Forwards and backwards reactions balance out.

Identifying Gases

• Hydrogen (H2): Produces a squeaky pop sound.
• Oxygen (O2): Relites a glowing splint.
• Carbon dioxide (CO2): Turns limewater cloudy.

Acids and Bases

• Acids release hydrogen ions. Alkalies produce hydroxide ions.
• Neutralization reaction: Acid + alkali = Salt + water.
• Universal indicator is used to determine the pH.

Explore the fundamentals of atomic structure and various separation processes such as filtration and crystallization in this quiz. Test your knowledge on concepts like atoms, elements, compounds, and different atomic models. Ideal for students studying chemistry or science classes.