Physical Science (24-25) PDF

# Unit 4 Part 1 ## Chemical Bonds: - Elements are normally found in compounds (not by itself) - Compound: Substance composed of different elements; mixture - Bonds: A persistent attraction between two or more atoms - Ionic: Electrostatic force between oppositely charged ions (crystal) - Co...

# Unit 4 Part 1 ## Chemical Bonds: - Elements are normally found in compounds (not by itself) - Compound: Substance composed of different elements; mixture - Bonds: A persistent attraction between two or more atoms - Ionic: Electrostatic force between oppositely charged ions (crystal) - Covalent: Sharing of electrons - Charges that are alike **REPEL** - Charges that are opposite **ATTRACT** ## Ionic Bonds: - Ions are charged (+ or -) - Ions attract (Coulomb's Law) - Ion Bond: Atoms gain or lose electrons to have a full valence shell - Stable structures when charges balance - Ion Crystal: A regular arrangement of atoms held together by attraction - Forms when multiple ion pairs attract each other - **Properties:** Hard, brittle, crystal, high melting point - Exist as crystals - Simple ions: Single atom that became charged ## Naming Compounds: - **Ionic Binary Compound: Single-Charged Cations** - Write metal first and then non-metal + Change ending to "ide" ## Ratios: - Compounds should be electrically neutral overall - Balancing ratios to neutralize compound - Example: Calcium Fluoride - Ca²⁺+ F^- "need two fluorine to neutralize - Therefore calcium fluoride is CaF₂ - Ionic compounds that are stable **MUST** be neutral. (Zero-Sum Rule) ## Polyatomic Ions (Compound): - Common Polyatomic Ions: | Ion's Name | Formula | Charge | |---|---|---| | Nitrate | NO₃^- | 1- | | Nitrite | NO₂^- | 1- | | Hydroxide | OH^- | 1- | | Bicarbonate | HCO₃^- | 1- | | Chlorate | ClO₃^- | 1- | | Carbonate | CO₃^2- | 2- | | Sulphate | SO₄^2- | 2- | | Phosphate | PO₄^3- | 3- | | Ammonium | NH₄⁺ | 1+ | - Polyatomic ions: Ions made of several; acts as a single ion. - Bonded covalently ## Naming Compounds: - **Polyatomic ions is...** - Behind: It's negative - In front: It's positive - >1: Write in brackets # Unit 4 Part 2 ## Covalent Bonds: - Made up of non-metals - Molecule: Covalent compounds - Crystal: Ionic compounds - Sharing electrons = **Covalent Bonds** - Allow them to all have a full outer shell - **Lewis' Dot Diagram** - H:H - Naming Covalent Compounds: - Written from left to right based on position on the PT - Ending changes to "ide" - Prefixes tell # of atoms of each type ## Diatomic Elements: - Common gases that exists in nature in single bond (pair) - Hydrogen - H₂ - Nitrogen - N₂ - Fluorine - F₂ - Oxygen - O₂ - Iodine - I₂ - Chlorine - Cl₂ - Bromine - Br₂ - How to remember: - Have - No - Fear - Of - Ice - Cold - Beer ## Video: chemical bond - **New Info Only** - Metals generally have 1-3 valence electrons - Non-metals generally have 4-8 valence electrons - Ionic bonds have high melting points due to requiring a lot of energy to break apart. - Same goes for covalent bonds ## Three Types of Covalent Compounds: 1. **Simple Covalent:** Weak intermolecular force - Low boiling point because its easy to break 2. **Giant Covalent:** Strong intermolecular force - High boiling point because it's harder to break 3. **Polymer:** More complex - connecting long chains of similar units ## Metallic Structures' atoms share electrons: - Electrons are de-localized and roam freely around structure - The positive nuclei form attraction with de-localized electrons - Very strong hence why it's so strong ## Other Information: ### Electrolytes: - Compounds that conduct electricity - Ionic compounds can conduct energy - Compounds separate into ions in water (charged) - Process is called dissociation - Covalent compounds can't conduct energy - Doesn't separate because they're not charged ### Molecular Shape: - 3D arrangement of atoms to showcase molecules ## Polarity + Electronegativity: - How unevenly distributed the electrons are in a covalent bond - **Polar Covalent Bond:** Electrons are shared unevenly. - : C::C: - **Non-polar Covalent Bond:** Electrons are shared approximately equally. - H:Cl: - Significantly greater electronegativity between atoms - Electrons are more pulled towards atom with higher electroneg. - Delta (δ): Greek letter that shows partial positive and negative parts - Electronegativity shown in periodic table - δ-= Partially negative (for atoms with more electron density) - δ+= Partially positive (for atoms with less electron density) ### Types of Covalent Bonds: - **Pure Covalent Bond:** Zero electronegativity difference between atoms (<0.4) - **Polar Covalent Bond:** Intermediate electronegativity difference between atoms (0.4-1.8) - **Ionic Bond:** Large electronegativity difference between atoms (>1.8) ## Difference in Ionic & Covalent - **IONIC** - Electroneg. difference bigger than 1.8-2.0 - Lower electroneg. atom gives valence electrons to other atom - The attraction force is the different charges in atoms - Non-metal and metal - **COVALENT** - Electroneg. difference smaller than 1.8-1.7 - Has at least one non-metal - Two atoms share valence electrons to form full outer shell - The attraction force is the atoms nuclei and electrons - Non-metal and non-metal ## Difference in Ionic & Covalent (Compound) - **IONIC** - Ionic bonds (from ions) form crystalline solids. - High melting + boiling point - Hard - Soluble in water, not non-polar liquid - Conducts electricity when dissolved in water or is a liquid - No odor + definite shape - Not crushable - Strong interparticle attractions - **COVALENT** - Covalent bonds form gas, solid, and liquid molecules - Low melting + boiling point - Soft - Polar = soluble in water - Non-polar = not soluble - Poor electrical conductors in all phases - Has odor + definite shape - Crushable - Weak interparticle attraction ## Covalent: Polar v.s. Non Polar - **POLAR** - Electroneg. difference bigger than 0.4-0.5. - Not stealing but hogging electrons - Electroneg. atom pulls electron to itself - **NON-POLAR** - Electroneg. difference smaller than 0.4-0.5 - Electrons are shared usually equally (same atoms = equal). - Both types of bonds have electronegativity difference of smaller than 1.8-1.7 - Both are types of covalent bonds.