MODULE-3-

Course and Institutional Overview

• Institution: Holy Infant College of Tacloban City, Inc.
• Address: Benigno Aquino Ave., Brgy. 50-B Youngfield, Tacloban City
• Administration: Owned and administered by the Religious Sisters of Mercy
• Department: Basic Education Department – Junior High School
• Subject: General Chemistry 1
• Academic Quarter & Year: 1st Quarter | SY: 2026-2027
• Lesson: Lesson 3 – Naming and Writing Chemical Formulas
• Subject Teacher: Jerwine Helaria, LPT
• Institutional Motto: In God’s Mercy, We Serve with Joy!

Lesson Objectives and Curriculum Framework

• Represent compounds using chemical formulas, structural formulas, and models.
• Name compounds given their chemical formulas, and write the chemical formulas of compounds given their systematic names.
• Practice naming ionic compounds and writing their corresponding chemical formulas.

Introductory Activity and Foundational Questions

• Matching Activity (Symbol Identification):

  • Sodium: $\text{Na}$
  • Chlorine: $\text{Cl}$
  • Calcium: $\text{Ca}$
  • Magnesium: $\text{Mg}$
  • Aluminum: $\text{Al}$
  • Oxygen: $\text{O}$
  • Potassium: $\text{K}$
  • Carbon: $\text{C}$
  • Nitrogen: $\text{N}$
  • Sulfur: $\text{S}$

• Element Charge Analysis Activity:

  • Elements evaluated for electron loss/gain and net charge determination: Sodium, Chlorine, Calcium, Magnesium, Aluminum, Oxygen, Potassium, Carbon, Nitrogen, Sulfur.

• Hook-Up Scenario:

  • Imagine assisting in a science laboratory where the teacher requests sodium chloride ($\text{NaCl}$) from a storage cabinet. Two containers are present: one labeled $\text{NaCl}$ and another labeled $\text{KCl}$. Both contain white crystals that appear visually identical. Selecting a container based purely on physical appearance or the generic term "salt" risks choosing the incorrect chemical substance.

• Laboratory Guide Questions:

  • How can we tell these substances apart?
  • What information does a chemical formula give us?
  • Why can't we rely only on the common name or appearance of a substance?
  • What could happen if a chemical substance were incorrectly identified or labeled?
  • How can knowing chemical symbols and formulas help us in everyday life?

• Substance Identification Questions:

  • Two labels say table salt and sodium chloride. How would you explain that they refer to the same substance?
  • Why might using only common names cause confusion in a chemistry laboratory?
  • How does knowing common names and chemical names help you recognize the chemistry of substances used in everyday life?

Foundations of Ionic Compounds and Oxidation Numbers

• Ionic Compound Definition:

  • Ionic compounds are chemical substances composed of positively charged ions (cations) and negatively charged ions (anions) held together by electrostatic attraction known as an ionic bond.
  • Ionic compounds commonly form when a metallic element transfers one or more valence electrons to a nonmetallic element.

• Oxidation Number:

  • Oxidation numbers are whole numbers related directly to the combining ratios of ions within a compound.

• Monatomic Ions Table:

  • Sodium ion: $\text{Na}^+$, charge $+1$
  • Potassium ion: $\text{K}^+$, charge $+1$
  • Magnesium ion: $\text{Mg}^{2+}$, charge $+2$
  • Calcium ion: $\text{Ca}^{2+}$, charge $+2$
  • Aluminum ion: $\text{Al}^{3+}$, charge $+3$
  • Chloride ion: $\text{Cl}^-$, charge $-1$
  • Oxide ion: $\text{O}^{2-}$, charge $-2$
  • Sulfide ion: $\text{S}^{2-}$, charge $-2$
  • Nitride ion: $\text{N}^{3-}$, charge $-3$

• Monovalent and Selected Polyatomic Ions Table:

  • Acetate ion: $\text{C}_2\text{H}_3\text{O}_2^-$ (listed as $\text{C}_2\text{H}_3\text{O}_3$)
  • Hypochlorite ion: $\text{ClO}^-$
  • Chlorite ion: $\text{ClO}_2^-$
  • Chlorate ion: $\text{ClO}_3^-$
  • Perchlorate ion: $\text{ClO}_4^-$
  • Cyanide ion: $\text{CN}^-$
  • Cyanate ion: $\text{CNO}^-$
  • Hydroxide ion: $\text{OH}^-$
  • Bicarbonate ion: $\text{HCO}_3^-$

Writing Chemical Formulas for Ionic Compounds

• Step-by-Step Procedure for Ionic Formulas:

  1. Write the symbol for the metal cation followed by the nonmetal anion, including their respective ionic charges. Always place the cation first.
  • Example 1: Potassium Chloride: $\text{K}^+$ and $\text{Cl}^-$
  • Example 2: Magnesium Fluoride: $\text{Mg}^{2+}$ and $\text{F}^-$
  1. Crisscross the numerical values of the charges to serve as subscripts for the opposite ion.
  2. Verify that the resulting ionic compound is electrically neutral by ensuring the sum of all positive charges equals the sum of all negative charges.

• Illustrative Practice Examples:

  • Aluminum bromide: $\text{AlBr}_3$
  • Lithium iodide: $\text{LiI}$
  • Sodium chloride: $\text{NaCl}$
  • Calcium iodide: $\text{CaI}_2$
  • Magnesium nitride: $\text{Mg}_3\text{N}_2$

• Boardwork Exercises:

  • Calcium bromide: $\text{CaBr}_2$
  • Sodium oxide: $\text{Na}_2\text{O}$
  • Magnesium phosphide: $\text{Mg}_3\text{P}_2$
  • Aluminum fluoride: $\text{AlF}_3$
  • Potassium oxide: $\text{K}_2\text{O}$

Polyatomic Ions and Naming Rules

• Definition of Polyatomic Ions:

  • A chemical element or grouping that exists as a molecular unit containing multiple atoms bound together.
  • They consist of multiple nonmetal atoms covalently bonded together that possess a net electrical charge due to gaining or losing electrons, maintaining stability as a charged ion group.

• Rules for Naming Polyatomic Ionic Compounds:

  1. Combine the full name of the cation directly with the name of the polyatomic anion.
  2. Format: Name of Cation + Name of Polyatomic Anion
  3. Example: $\text{KNO}_2$ is named Potassium nitrite.

• Illustrative Examples:

  • Aluminum sulfate: $\text{Al}_2(\text{SO}_4)_3$
  • Zinc hydroxide: $\text{Zn}(\text{OH})_2$
  • Potassium nitrate: $\text{KNO}_3$
  • Sodium bicarbonate: $\text{NaHCO}_3$

• Boardwork Exercises:

  • Sodium nitrate: $\text{NaNO}_3$
  • Potassium sulfate: $\text{K}_2\text{SO}_4$
  • Calcium carbonate: $\text{CaCO}_3$
  • Magnesium hydroxide: $\text{Mg}(\text{OH})_2$
  • Barium nitrate: $\text{Ba}(\text{NO}_3)_2$
  • Aluminum sulfate: $\text{Al}_2(\text{SO}_4)_3$

Naming Binary Ionic Compounds

• Definition:

  • Binary compounds are chemical compounds constructed from exactly two different chemical elements.

• Naming Rules:

  • Name the metal cation first, followed by the nonmetal anion.
  • Truncate the nonmetal element name to its root word and append the suffix -ide.
  • General Equation: Metal + Nonmetal root + ide

• Illustrative Examples:

  • $\text{Na}_2\text{O}$: Sodium oxide
  • $\text{CaCl}_2$: Calcium chloride
  • $\text{BaCl}_2$: Barium chloride
  • $\text{CsF}$: Cesium fluoride
  • $\text{LiCl}$: Lithium chloride
  • $\text{CdS}$: Cadmium sulfide

Alternative Nomenclature Systems: Stock System and Classical Method

• Stock System (Roman Numerals):

  • Uses Roman numerals written in parentheses immediately following the metal name to represent the specific oxidation charge of the transition metal.
  • Applied to metals capable of forming multiple ionic charges.
  • Examples:
  • $\text{FeO}_3$: Iron(III) oxide (listed as $\text{FeO}_3$)
  • $\text{FeCl}_2$: Iron(II) chloride
  • $\text{CuCl}$: Copper(I) chloride
  • $\text{CuCl}_2$: Copper(II) chloride

• Classical Method (Latin Roots and Suffixes):

  • Uses specific Latin root names combined with variable suffixes to indicate charge status:
  • Suffix -ic: Applied when the metal cation is in its higher oxidation charge state.
  • Suffix -ous: Applied when the metal cation is in its lower oxidation charge state.
  • Examples:
  • $\text{FeBr}_3$: Ferric bromide / Ferric oxide
  • $\text{FeBr}_2$: Ferrous chloride / Ferrous bromide
  • $\text{CuCl}$ (lower charge): Cuprous chloride
  • $\text{CuCl}_2$ (higher charge): Cupric chloride

Latin Etymology of Chemical Elements

• Gold: Symbol $\text{Au}$, Latin Name: Aurum, Meaning: "Shining dawn"

• Silver: Symbol $\text{Ag}$, Latin Name: Argentum, Meaning: "Shiny" or "white"

• Copper: Symbol $\text{Cu}$, Latin Name: Cuprum, Meaning: From Cyprus (where it was mined)

• Lead: Symbol $\text{Pb}$, Latin Name: Plumbum, Meaning: "Soft metal" (used in pipes)

• Tin: Symbol $\text{Sn}$, Latin Name: Stannum, Meaning: Old word for tin alloy

• Sodium: Symbol $\text{Na}$, Latin Name: Natrium, Meaning: From natural soda

• Potassium: Symbol $\text{K}$, Latin Name: Kalium, Meaning: From alkali

• Antimony: Symbol $\text{Sb}$, Latin Name: Stibium, Meaning: Ancient name for a black cosmetic

• Mercury: Symbol $\text{Hg}$, Latin Name: Hydrargyrum, Meaning: "Liquid silver"

• Iron: Symbol $\text{Fe}$, Latin Name: Ferrum, Meaning: "Iron" in Latin

• Comparative Nomenclature Table (Stock vs. Classical):

  • $\text{FeS}$: Stock Name: Iron(II) sulfide, Classical Name: Ferrous sulfide
  • $\text{Fe}_2\text{S}_3$: Stock Name: Iron(III) sulfide, Classical Name: Ferric sulfide
  • $\text{Cu}_2\text{S}$: Stock Name: Copper(I) sulfide, Classical Name: Cuprous sulfide
  • $\text{CuS}$: Stock Name: Copper(II) sulfide, Classical Name: Cupric sulfide
  • $\text{SnO}$: Stock Name: Tin(II) oxide, Classical Name: Stannous oxide
  • $\text{SnO}_2$: Stock Name: Tin(IV) oxide, Classical Name: Stannic oxide
  • $\text{PbO}$: Stock Name: Lead(II) oxide, Classical Name: Plumbous oxide
  • $\text{PbO}_2$: Stock Name: Lead(IV) oxide, Classical Name: Plumbic oxide

Formative Questions and Conceptual Scenarios

• Exit Question: How does knowing the charges of ions allow us to correctly write the formula and name of an ionic compound?
• One-Sentence Exit Reflection Prompt: "Today, I learned that correctly naming and writing ionic compounds requires me To _______ because __________ ."
• Formative Questions for Covalent Compounds:
  • A student names $\text{CO}$ as carbon dioxide. Is the student correct? Explain your answer.
  • A student writes $\text{N}_2\text{O}_3$ for nitrogen dioxide. What is wrong with the student's formula?
  • Why does $\text{CO}$ have a different name from $\text{CO}_2$, even though both contain carbon and oxygen?
  • A compound is named dinitrogen tetroxide. How can the prefixes help you determine its formula?
  • How does understanding prefixes help you move from a compound's name to its chemical formula?

Naming Binary Covalent Compounds and Greek Prefixes

• Covalent Compound Definition:

  • Compounds formed when two or more nonmetal atoms share valence electrons, forming covalent bonds.

• Greek Prefixes:

  • Used to specify the exact number of atoms of each element present in a binary covalent molecule.
  • Allows formula determination without calculating ionic charges.
  • Mono = $1$
  • Di = $2$
  • Tri = $3$
  • Tetra = $4$
  • Penta = $5$
  • Hexa = $6$
  • Hepta = $7$
  • Octa = $8$
  • Nona = $9$
  • Deca = $10$

• General Rule for Naming:

  • General Equation: Prefix + Name of 1st Nonmetal + Prefix + Name of 2nd Nonmetal root + ide

• Illustrative Practice Examples:

  • $\text{CO}_2$: Carbon dioxide
  • $\text{H}_2\text{O}$: Dihydrogen monoxide
  • $\text{NH}_3$: Nitrogen trihydride
  • $\text{SO}_3$: Sulfur trioxide
  • $\text{PCl}_3$: Phosphorus trichloride
  • $\text{Cl}_2\text{O}$: Dichloride monoxide
  • $\text{BF}_3$: Boron trifluoride
  • $\text{N}_2\text{O}_4$: Dinitrogen tetroxide