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Atomic Structure of Matter

• Dalton's atomic model depicts the atom as a solid, indivisible sphere.
• Thomson's model portrays the atom as a positively charged sphere with negatively charged electrons embedded within it. The positive charge balances the negative charge of the electrons.
• Rutherford's model places protons in the nucleus, with the number of negatively charged electrons equaling the number of positively charged protons. Electrons orbit the nucleus.

Rutherford's Model Failures

• Electrons, if stationary, would be attracted to the positively charged nucleus and collapse into it.
• If electrons are moving, they lose energy during movement, slowing and spiraling into the nucleus, causing atomic collapse. However, atoms do not collapse.

Quantum Theory

• Electrons exist in specific energy levels around the nucleus.
• Electrons orbit the nucleus in distinct energy levels.

Orbitals

• Orbitals are regions of space surrounding the nucleus where an electron is likely to be found.
• Orbitals are electron clouds surrounding the nucleus.

Modern Theory Postulates

• The atom consists of a nucleus surrounded by electrons in different energy levels.
• Electrons revolve around the nucleus in specific energy levels.
• Electrons do not repel when found in the same orbital due to opposite spin directions.

Aufbau Principle and Hund's Rule

• Aufbau principle: Electrons fill lower energy levels before higher ones.
• Hund's rule: Electrons individually occupy each orbital in a sublevel before pairing up.

Lewis Symbols

• Lewis symbols visually represent the valence electrons in an atom's outermost shell.

Representative Elements

• Representative elements have partially filled s and p sublevels in their outermost shells; noble gases are an example.

Atomic Radius

• Atomic radius (or atomic size) is half the distance between the nuclei of two identical, bonded atoms.

Ionization Energy

• Ionization energy is the energy needed to remove an electron from the outermost energy level of a neutral gaseous atom.

Periodic Table Groups

• Group 1: Alkali metals
• Group 2: Alkaline earth metals
• Group 7: Halogens
• Group 8: Noble gases

Periodic Table Blocks

• s block: Left side of the periodic table; two groups.
• p block: Right side of the periodic table; six groups, with group 8 being the noble gases.
• d block: Middle of the periodic table; transition elements.
• f block: Bottom of the periodic table; inner transition elements.

Periodic Trends

• Across a period: Atomic radius decreases and ionization energy increases due to increasing nuclear attraction.
• Down a group: Atomic radius increases and ionization energy decreases due to increasing electron shielding.

Why is ionization energy greater in case [0] than in case [3]?

• [3] has a half-filled sublevel (p-orbital), which is less stable than a completely filled sublevel.

Calcium Existence

• Calcium is not found free in nature due to its high reactivity.
• Calcium is found combined with other elements, such as in carbonates (e.g., marble, limestone), sulfates (e.g., gypsum), phosphates (e.g., calcium phosphate), and silicates.

Calcium Extraction

• Calcium is extracted through the electrolysis of molten calcium fluoride or calcium chloride.

Calcium Uses

• Calcium is found in dairy products (e.g., milk) and some seafood.

Calcium Oxide (CaO)

• Calcium oxide (CaO) is also known as quicklime or lime.

Calcium Hydroxide (Ca(OH)₂

• Calcium hydroxide (Ca(OH)₂) is known as slaked lime.
• Pure calcium hydroxide (Ca(OH)₂) is called clear limewater.

Preparation of Calcium Hydroxide

• Slaking lime is the process of adding water (H₂O) to calcium oxide (CaO) to form calcium hydroxide (Ca(OH)₂).

Reaction of Calcium Hydroxide with Carbon Dioxide

• Calcium hydroxide (Ca(OH)₂) turns milky (cloudy) when carbon dioxide (CO₂) is passed through it due to the formation of a white precipitate of calcium carbonate (CaCO₃).

Gypsum Types

• Gypsum (CaSO₄⋅2H₂O): Commonly used in construction.
• Plaster of Paris (CaSO₄⋅½H₂O): Made by heating gypsum until it loses water. Used in construction, plastering, and sculpting.

Sodium (Na) Properties

• Soft metal
• Silver-colored when freshly cut
• Density less than water
• Melts at 97.81 °C
• Boils at 882.9 °C

Sodium Reactivity in Air

• Sodium's luster disappears when exposed to air and moisture due to reacting with oxygen.

Sodium Extraction

• Sodium chloride (NaCl) is mined underground.

Sodium Extraction from Seawater

• Seawater is pumped into evaporation ponds and heated by the sun to precipitate out the sodium salt crystals.

Sodium Hydroxide (NaOH) Properties

• Solid
• Absorbs moisture from air.
• Reacts with CO₂ to form a dry sodium carbonate layer.

Lithium Solubility in Water

• Lithium's low solubility in water is due to its small size and strong nuclear attraction to its electrons.

Group 1 & 2 Elements

• Low electronegativity and low ionization energy
• Group 1 elements have one valence electron; Group 2 has two.
• Both groups are highly reactive and not found free in nature.

Comparing Metallic Character

• Barium is more metallic than beryllium due to a larger atomic radius and thus lower ionization energy.

Flame Tests

• Flame tests use different colored flames when heated:
  • Lithium: Crimson (red)
  • Strontium: Crimson (red)
  • Sodium: Bright yellow
  • Calcium: Brick-red
  • Barium: Pale green

Identifying Sodium Ions

• Sodium ions produce a yellow flame color in a flame test.

Aluminum Extraction

• Bauxite (Al₂O₃⋅nH₂O) is the primary ore for aluminum production.
• Cryolite (Na₃AlF₆) is used to facilitate aluminum extraction.

Aluminum's Resistance to Corrosion

• Aluminum does not corrode completely due to forming a protective aluminum oxide layer (Al₂O₃).
• The aluminum oxide layer restricts acids from the aluminum reacting with it further.

Thermite Reaction

• Thermite reaction involves aluminum reducing iron oxide (Fe₂O₃) with heat released.
  • (2Al + Fe₂O₃ → Al₂O₃ + 2Fe + heat)
• Used in welding large iron structures and railroad rails.

Aluminum Alloys

• Duralumin: High aluminum content with copper and other metals; resistant to corrosion, used in decorative items.
• Aluminum bronze: Low aluminum content with copper; lightweight and strong; used in aircraft parts.

Aluminum Hydroxide (Al(OH)₃) Preparation

• Aluminum hydroxide can be prepared by reacting an aqueous solution of aluminum sulfate (Al₂(SO₄)₃) with sodium hydroxide (NaOH).

Aluminum Oxide (Al₂O₃) Preparation

• Aluminum oxide can be prepared by heating aluminum hydroxide(Al(OH)₃).

Aluminum Oxide Uses

• Polishing and cleaning metals.
• Gemstone crafting.

Alum

• Alum (potassium aluminum sulfate) is a double salt. It is formed by mixing potassium sulfate and aluminum sulfate solutions, allowing the water to evaporate, and producing crystals of alum with water molecules attached.

Alum Uses

• Wound disinfection
• Blood clotting
• Dye fixing in fabrics
• Water purification

Acids and Aluminum

• Aluminum reacts with dilute hydrochloric acid, producing hydrogen gas and aluminum chloride.

Solutions and Concentration

• Solutions are homogeneous mixtures of two or more substances.
• Solute is the substance present in smaller amount.
• Solvent is the substance present in larger amount.

Solution Types

• Liquid solutions: Dissolving a solid in a liquid (e.g., salt in water), a liquid in a liquid (e.g., alcohol in water), a gas in a liquid (e.g., HCl gas in water).
• Solid solutions: Dissolving a solid in a solid (e.g., alloys).
• Gas solutions: Dissolving a gas in a gas (e.g., air).

Types of Solutions by Concentration

• Concentrated solution: High solute concentration.
• Dilute solution: Low solute concentration.
• Converting a concentrated to dilute solution: Add solvent.
• Converting a dilute to concentrated solution: Add solute.

Types of Solutions by Solubility

• Saturated solution: Maximum amount of solute dissolved at a given temperature and pressure.
• Unsaturated solution: Less than maximum solute dissolved.
• Supersaturated solution: More than maximum solute dissolved; unstable and precipitates excess solute.

Electrolyte and Non-Electrolyte Solutions

• Electrolyte: Solute ions in solution; strong (completely ionized) or weak (partially ionized).
• Non-electrolyte: Solute does not ionize in solution (e.g., sugar, ethyl alcohol).

Solubility Factors

• Nature of solute and solvent.
• Temperature.
• Pressure (mostly for gases dissolved in liquids).

Effect of Stirring/Agitation on Solubility

• Stirring increases surface area of solute exposed to solvent, thus accelerating the dissolution process.
• Stirring increases contact time; rate of dissolving increases.

Effect of Particle Size on Solubility

• Smaller particle size (e.g., powdered sugar) increases the surface area exposed to the solvent and thus increases the rate of dissolving.

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