Science 10 Chemistry Study Guide: Atoms, Elements, and Compounds

Course Overview and General Learning Structure

• The course is organized by weeks, focusing on specific learning outcomes that serve as the primary guide for instruction and assessment. Priority learning outcomes are emphasized to ensure core competency acquisition. • Curriculum delivery includes daily synchronous topics, tasks, and assessments designed to address learning outcomes and develop essential scientific skills and processes. • Educators and designers facilitate learning based on student needs, recommending specific tasks that may shift based on contextual requirements.

Introduction to Chemistry and Real-World Applications

• Chemistry is the study of matter and the changes it undergoes, exploring fundamental questions about the nature of substances and why they react. Understanding chemistry is essential to understanding the physical world. • Real-world examples of chemical processes include:   • Fermentation: Chemical reactions that convert sugar into alcohol and $CO_2$.   • Medicine: The formation and synthesis of substances used to treat illnesses.   • Industrial Production (e.g., Methanex Company): Combining natural gas and steam to create industrial chemicals.   • Agricultural Chemistry (e.g., Canadian Fertilizer Company): Mixing specific ratios of chemicals to optimize plant growth.

Workplace Hazardous Materials Information System (WHMIS)

• The primary purpose of WHMIS is to reduce workplace and laboratory injury and illness. • WHMIS legislation ensures that individuals working with chemicals are trained to:   • Handle chemicals safely.   • Dispose of chemicals safely. • Hazard Symbols and Their Meanings:   • Exploding Bomb: Represents explosion or reactivity hazards.   • Flame: Indicates fire hazards for flammable and combustible materials.   • Flame Over Circle: Represents oxidizing materials that provide oxygen, causing other materials to burn or explode.   • Gas Cylinder: Indicates gases stored under pressure.   • Corrosion: Symbolizes materials that cause corrosive damage to metals, skin, or eyes.   • Skull and Crossbones: Indicates acute toxicity that can cause death or severe toxicity with short exposure to small amounts.   • Health Hazard: Represents materials suspected of causing serious health effects such as carcinogenicity, mutagenicity, or respiratory sensitization.   • Exclamation Mark: Indicates materials that cause less serious health effects or damage to the ozone layer (e.g., irritants).   • Biohazardous Infectious Materials: Pertains to biological organisms or toxins that can cause disease in people or animals.   • Environmental Hazard: Indicates materials destructive to the aquatic environment or ozone layer. Note: This group was not adopted in WHMIS 2015 but may still appear on Labels/SDSs.   • Aspiration Hazard: Materials that cause pulmonary injury if breathed in.   • Dangerously Reactive Material: Specifically for unstable materials undergoing unexpected reactions.

Material Safety Data Sheets (MSDS)

• An MSDS is shipped with every chemical and contains comprehensive safety information including:   • Scientific and common names.   • Physical properties.   • Chemical hazards.   • Handling, storage, and disposal instructions.   • Emergency procedures and first aid. • Case Study: Acetone MSDS (Flinn Scientific, Inc.) Details:   • Synonyms: Dimethyl ketone, 2-Propanone. CAS#: $67-64-1$.   • Hazards: Class 1B flammable liquid. IRritating to tissues. Toxic if ingested. Vapors cause fatigue/nausea.   • NFPA Code: Health (1), Flammability (3), Reactivity (0).   • Fire Fighting: Flash point of $-17^\circ C$. Uses triclass dry chemical extinguishers.   • First Aid: Flush eyes/skin for $15$ minutes. Do NOT induce vomiting if swallowed.   • Exposure Guidelines: PEL $1000\,ppm$, TWA $500\,ppm$, STEL $750\,ppm$.

Classification of Matter

• Matter is defined as anything with mass and volume, existing as solid, liquid, or gas. • Pure Substances: Matter with a definite composition.   • Elements: Substances that cannot be chemically broken down into simpler forms.   • Compounds: Two or more elements chemically combined; can be separated chemically. • Mixtures: Combinations of matter separable by physical means with variable composition.   • Heterogeneous (Mechanical Mixture): Different components are visible; composition varies throughout.   • Homogeneous (Solution): Components are not visible; composition is constant throughout.

Changes in Matter

• Physical Change: A substance changes form but not chemical composition. No new substances are formed. Examples: cutting carrots, melting ice, dissolving iced tea. • Chemical Change: Atomic/molecular structures change as bonds are broken and reformed to create new substances. These are difficult/impossible to reverse. Examples: iron rusting, milk souring, wood burning. • Learning Check Examples:   • Ice tea dissolves (Physical).   • Carrot cut (Physical).   • Dying hair (Chemical).   • Water to steam (Physical).   • Iron rusts (Chemical).   • Popcorn popping (Chemical).

Historical Development of Atomic Theory

• Aristotle: Proposed all matter was made of Earth, Water, Air, and Fire. • Democritus: Proposed ‘atomos’—tiny, indivisible particles. His ideas were largely ignored for $2000$ years until the scientific method developed. • Antoine Lavoisier: Discovered the Law of Conservation of Mass (matter is not created or destroyed in reactions). • John Dalton (1808) – ‘Billiard Ball’ model:   • All matter is made of atoms.   • Atoms are indivisible.   • Atoms of an element are identical in mass/size.   • Compounds form in fixed proportions. • J.J. Thomson – ‘Raisin Bun’ model:   • Used the Cathode Ray Tube to discover negative particles (electrons).   • Proposed the atom is a positive sphere with embedded negative electrons. • Ernest Rutherford (1909) – ‘Planetary’ model:   • Gold Foil Experiment: Fired alpha ($+$) particles at thin gold. Most passed through, but some bounced back.   • Conclusion: Atoms are mostly empty space with a tiny, dense, positive nucleus.   • James Chadwick (working under Rutherford) discovered the neutron to explain why Helium is $4\times$ heavier than Hydrogen. • Niels Bohr (1913) – ‘Energy Level’ model:   • Electrons orbit the nucleus in fixed energy levels/shells and cannot exist in between levels.

Atomic Structure and the Periodic Table

• Subatomic Particles:   • Proton ($p^+$): $1+$ charge. Found in nucleus.   • Neutron ($n^0$): $0$ charge. Found in nucleus.   • Electron ($e^-$): $1-$ charge. Negligible mass, orbits nucleus. • Calculations for Neutral Atoms:   • \text{# of protons} = \text{Atomic Number}   • \text{# of electrons} = \text{# of protons}   • \text{# of neutrons} = \text{Mass Number} - \text{Atomic Number} • Isotopes: Atoms of the same element (same protons) with different masses (different neutrons). Named as ‘Element-Mass #’ (e.g., Carbon-14). • Periodic Table Organization:   • Developed by Dmitri Mendeleev.   • Periods: Horizontal rows ($1-7$).   • Groups/Families: Vertical columns ($1-18$).   • Staircase Line: Separates metals (left) from non-metals (right). Metalloids sit on the line.

Elemental Families and Properties

• Group 1: Alkali Metals – Shiny solids, soft, highly reactive with water. • Group 2: Alkaline Earth Metals – Shiny solids, reactive, form oxides. • Group 17: Halogens – React with metals to form salts. Can be gas ($F, Cl$), liquid ($Br$), or solid ($I$). • Group 18: Noble Gases – Colorless gases, extremely stable/unreactive because they have a ‘stable octet’ (full valence shell). • Malleability: Ability to be shaped by pressure. • Ductility: Ability to be stretched into wire.

Electron Arrangement and Diagrams

• Bohr Diagrams: Show all electrons in specific orbits. Rule: Max $2e^-$ in 1st level, max $8e^-$ in 2nd level, max $8e^-$ in 3rd level. • Energy Level Diagrams: Simplified text representations of Bohr diagrams (e.g., Lithium: $1e^-, 2e^-$ written beside the symbol). • Lewis Dot Diagrams: Represent the nucleus and inner shells with the symbol, surrounded by dots for valence electrons (outer shell). • Valence Electrons: The number of electrons in the outer shell. In main groups, the last digit of the group number equals the number of valence electrons (e.g., Group 15 has $5$ valence electrons).

Chemical Bonding and Compound Formation

• Ion Formation:   • Atoms gain or lose electrons to achieve a stable octet (like the nearest noble gas).   • Cation: Positively charged ion formed when a metal loses electrons.   • Anion: Negatively charged ion formed when a non-metal gains electrons. • Ionic Compounds: Formed via electron transfer between a metal and non-metal. Held by strong ionic bonds in a crystal lattice. • Molecular Compounds: Formed when non-metals share electrons via covalent bonds. They exist as independent molecules rather than lattices. • Diatomic/Polyatomic Elements: Atoms of the same element sharing electrons (e.g., $Cl_2$, $CO_2$ (compound)).

Learning Checks and Self-Assessment

• Identify common properties: Noble gases are non-reactive due to a full valence level. • Identify atomic structure: Element ‘X’ with $18$ protons and mass of $40$ is Argon ($Ar$). It has $18$ protons, $22$ neutrons, and belongs to Group 18, Period 3. • Compound Classification Checklist:   • $NaCl$ (Ionic)   • $H_2O$ (Molecular)   • $LiF$ (Ionic)   • $CO_2$ (Molecular)   • $MgBr_2$ (Ionic)