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Understanding Chemical Bonds: Elements, Compounds, and Formulas

Explore the fundamentals of chemical bonding, including the types of bonds, formulas, and compounds that elements form to achieve stability. Learn how ionic and covalent bonds differ and practice naming compounds correctly.

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Understanding Chemical Bonds: Elements, Compounds, and Formulas

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  1. Warm-up 3/21/11 • Review questions: List as many elements as you can think of. Then list as many compounds as you can think of. • Teach the teacher questions: If you could start a band what kind of band would you start, what would you call it, and what part would have in it (play guitar, sing, ect.). • Learning Targets: By the end of the class you should know: what happens when elements combine • the two different kinds of bonds • how to balance cations and anions for a chemical bond

  2. Chemical Bonds Bonding isn’t just for people.

  3. Why do atoms form compounds? • TO BECOME STABLE!! • What does stable mean to an atom? • Full set of valence electrons • Atoms want to have the electron configuration of a noble gas • Atoms will gain, lose or share electrons in order to obtain a full set of valence electrons • Chemical bonding

  4. → Combining Elements • The chemical & physical properties of the elements are different than the properties of the compound they make up • Na + Cl2→ NaCl • Reaction of Sodium with Chlorine & Hydrogen with Oxygen

  5. Types of Bonds • Ionic Bonds • Contain a metal & a nonmetal (at least 1 of each) • Electrons are gained or lost • Ex. Salt, NaCl • Covalent Bonds • Contain 2 or more nonmetals or hydrogen • Electrons are shared • Ex. Water, H2O

  6. Ionic Bonding • In an ionic bond, one atoms gives electrons to another atom. • When atoms combine this way, it is called a formula unit. • Ex. NaCl is a formula unit • The charge of a formula unit is always 0. • The positive and negative charges must always balance each other.

  7. Formulas • Chemical Formula—tells what elements a compound contains and the exact number of the atoms of each element. • Ex. NaCl has 1 atom of sodium & 1 atom of chlorine • Ex. H2O has 2 atoms of hydrogen and 1 atom of oxygen. • A subscript (small # written below) is written after a symbol to tell how many atoms of that element are in the compound.

  8. Rules for Formulas • Write the cation (metal) first. Write the anion (nonmetal) second. • The net ionic charge is zero. • Use subscripts to indicate multiple ions. • Write the formula unit in the lowest whole number ratio.

  9. A trick for formula units • Write both ions with their charges as superscripts. Cu3+ & O2- • Crisscross the charges to make the subscripts in the formula • Do not put + or – in the formula • Cu3+ & O2- Cu2O3

  10. Silver Chloride Ag+1 Cl-1 AgCl

  11. Zinc Phosphide Zn+2 P-3 Zn3P2

  12. Aluminum Oxide Al+3 O-2 Al2O3

  13. Warm-Up 3/24/11 • Review: Give an example of a formula unit. • Teach the Teacher: What is the best holiday? Are you going to the pow wow?

  14. Flash card • On the front write: • subscript • On the back write: • H2O (submarine)

  15. Flash card • On the front: • Ionic Bonding • On the back: • When an element gains or loses an electron

  16. Flash Card • On the front: • Covalent bonding • On the back: • When atoms share electrons

  17. Warm-Up 3/25/11 • Review questions: What is an ionic bond? (use your flash cards) • Teach the teacher questions: Would you rather be stuck in an elevator with wet dogs or wet cats? • Learning Targets: By the end of the class you should know: polyatomic ions

  18. Practice with Chemical Formulas Common Name Chemical Formula Types & Number of Elements involved • Sand SiO2 • Milk of MagnesiaMg(OH)2 • Sucrose C12H22O11 • Vinegar HC2H3O2 • Ethanol C2H5OH →

  19. Chemical Bonds • IONIC BONDS • between metals & nonmetals • Electrons form a give take relationship • metals give e- (cation) • nonmetal take e- (anion) • Held together by attraction of opposite charges IONIC ANIMATION Types of Bonds

  20. Table Polyatomic Ions PolyatomicIons • The prefix poly- means many in Greek. • ion consisting of a molecule with many covalently bonded atoms • act as a single unit • polyatomic ion is also referred as a radical • Usually end in –ate & –ite • -ide usually indicates binary compounds

  21. Oxidation number—the charge of an ion 1+ 2+ 3+ 3- 2- 1-

  22. Multiple Oxidation Numbers • Some metals (other metals & transition metals) can have more than 1 oxidation number. • If an element can have more than 1 oxidation number, the charge of the ion is written as a roman numeral in parentheses. • Ex. Copper (I) ion is Cu1+ • Copper (II) ion is Cu2+

  23. Roman numerals are not written in the formula • Charges are not written in the formula • Don’t drop polyatomic subscripts • Hydroxide, OH, needs parentheses to indicate multiples. • Cu(II)O CuO • K+1Br-1KBr • CaNO2 Ca(NO3)2 • CaOH2 Ca(OH)2 Mistakes to Avoid

  24. Ionic Compounds Group A Elements Write the cation name 1st • Cation name is the same as the element name Write the anion name 2nd • Change the ending of the name to –ide. Rules for Naming

  25. Flash Card • On the front write: • Polyatomic Ion • On the back write: • Ion consisting of many covalently bonded atoms

  26. WBC • Zinc Fluoride • Zn+2 • F-1

  27. WBC • Plumbous Bromide • Pb+2 • Br-1

  28. WBC • Stannous Sulfide • Sn+2 • S-2

  29. WBC • Silver Phosphide • Ag+1 • P-3

  30. WBC • Lead (II) Bromide • Pb+2 • Br-1

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