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Chemical Reactions and Compound Formation

Learn about chemical reactions, compounds, and the different types of bonding. Understand the importance of names in everyday life.

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Chemical Reactions and Compound Formation

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  1. Chapter 3 Elements Combine to Form Compounds

  2. Chapter 3 3.1 Compounds

  3. Chemical Reaction What are the indicators that a chemical reaction has occurred? • Potassium Chlorate and a Gummy Bear

  4. In your INB notebooks or WB to create the following table What charge will be on the following atoms? Will the atoms GAIN or LOSE electrons to become stable? How many electrons? Ion Charge? Element Metal or Non-meta Valence Electrons G Metal Lose 1 e- 1+ Metal Lose 2 e- 2+ Non -metal Gain 1 e- 1- Non -metal Gain 2 e- 2- Non -metal Gain 3 e- 3-

  5. Ion Charge Revisited What determines the ion charge or combining capacity for a particular element? • The ion charge is determined by the number of valence e- in the outer shell that an element wants to donate or borrow (lose or gain). Example: Ca = +2 Na = +1 Cl = -1 What are Ions? - video clip

  6. Metals vs. Nonmetals From the periodic table, can you locate metals and nonmetals? What type of ions do metals form? • Metals have positive (+) charges. • They want to donate (give) an e- (or electrons)from their outer shell. What type of ions do nonmetals form? • Most non-metals have negative (–) charges. • They want to accept (gain) an e- (or electrons)into their outer shell.

  7. What is a Compound? • Molecules are pure substances made of only one type of atom held together by chemical bonds. Example: Diatomic elements H2, N2, O2, F2, Cl2, Br2, I2 • Compounds are pure substances made of more than one type of atom held together by chemical bonds. CO2, H2O • Most compounds are one of 2 basic types: • Covalent • Ionic

  8. Determining Ionic vs. Covalent Compounds What do you think is the main difference between the elements in the ionic compound and the elements in the covalent compound shown below? Answer this question in your INB notebook .

  9. Covalent Compounds • Atoms combine by sharing valence electrons Example. Water • Covalent bonding usually occurs between at least 2 non-metals. • Example: C and O share electrons to form CO2 (carbon dioxide) – try to draw it!

  10. Ionic Compounds • Atoms gain or lose electrons and form ions (- or +). • The charges of the ions are attracted to the opposite charge; therefore a compound is produced. • Attraction and bond between a metal (+ ion) and non-metal (- ion) to produce/form a compound. • Example. Na+ and Cl- combine to form NaCl (salt) NOTE: • In covalentcompounds, atoms combine by sharing electrons to form molecules.

  11. Covalent vs. Ionic Bonding • Covalent vs. Ionic Compounds - video clip • What are Ionic Bonds (The Fuse School) - video clip • Ionic Bonds - video clip

  12. Ionic Bonds • Lead to the formation of crystal lattices. • All the ions are attracted to all other ions in the crystal, although nearest ions have the greatest attraction. • Repeating pattern of negative and positive charges. • Think in terms of ratios. • NaCl is a ratio of one sodium to one chlorine, but many NaCl molecules will form a crystal lattice.

  13. Two Representations of Crystal Lattices

  14. Carefully examine the information in the table below. Write answers in INB. • What do you think the subscripts in the chemical formulas represent? • The subscripts indicate the number of each atom in the compound. • How many of a particular atom are present in a compound when there is no subscript written? • The absence of a subscript indicates that there is one of that particular atom in the compound.

  15. Chemical Formula A compound is a substance made up of a definite proportion of two or more elements. A chemical formula tells us the number of atoms of each element in a compound. Subscripts - indicate the number of each atom present in a compound • subscripts are placed AFTER the atom that they refer to. Example: Al2S3 2 Al atoms 3 S atoms Total atoms 2 + 3 = 5 The absence of a subscript after an atom indicates that there is one atom present - the “1” subscript is never written. NaCl(1 Na and 1 Cl)

  16. Chemical Formula Subscripts When brackets are placed around atom groups in a compound, the subscript after the brackets indicates the number of atom groups in a compound. Example: Al2(SO4)3 Indicates # of“SO4” groups (3 groups) A subscript outside (and after) a bracket - multiply all the elements inside the brackets by that #. Example: Ba3(PO4)2 3 Barium atoms; 1 x 2 = 2 Phosphorus Atoms; 4 x 2 = 8 Oxygen Atoms Total = 3 + 2 + 8 = 13 atoms

  17. Chemical Formula Scripts

  18. Names in Everyday Life Write your answers in your INB notebook Names are important in every part of our lives. Write a few sentences to explain the importance of names in each of the following aspects of your life. WHY ARE CLEAR, UNIQUE NAMES IMPORTANT IN EACH CASE? • Getting around: streets, cities, towns, landmarks • Communicating: conversation, social media, messaging • Consuming: product and brand names; names of medications; names of books, songs, and movies NOTE: The international system for naming chemicals is maintained by the International Union of Pure and Applied Chemistry (IUPAC).

  19. How do we name Ionic Compounds? In your INB, state what you notice about the following ionic compound names. Sodium Chloride NaCl Magnesium Oxide MgO Potassium Sulphide K2S Barium Bromide BaBr2

  20. Naming Simple Ionic Compounds • Write the metal (+ ion) name first • As found on the periodic table 2. Write the non-metal (- ion) name second • Change the last few letters to “ide” • “ide” is a suffix (goes at the end of the word) Example: NaCl → sodium chloride Example: MgO → magnesium oxide

  21. Naming Covalent Compounds ·In covalent compounds, prefixes are used to tell a person how many of element there is. Below is a list of covalent prefixes: 1 = mono 2 = di 3 = tri 4 = tetra 5 = penta 6 = hexa 7 = hepta 8 = octa 9 = nona 10 = deca A prefix goes at the beginning of a word.

  22. Naming Covalent Compounds • Write the name of the first non-metal with the proper prefix for how many non-metals there are (the subscript #). NOTE: No “mono” prefix for the first non-metal Example: CO (carbon monoxide) 2. Write the name of the second non-metal ending in “ide” with the proper prefix for how many non-metals there are (the subscript #). Example: N2Cl4 (dinitrogen tetrachloride) • N is nitrogen and the prefix for two is “di” • Cl is chloride and the prefix for four is “tetra”

  23. Writing Formula of Ionic Compounds Although an ionic compound is made up of ions, overall the compound is electrically neutral (no charge). • The positive charges on the metal ions must balance the negative charges on the non-metal ions. NaCl MgCl2 Al2O3 1 Na+ ion: 1 Cl- ion 1 Mg2+ ion: 2 Cl- ion 2 Al3+ ion: 3 O2-ion O2- Cl- Al3+ Na+ O2- Cl- Mg2+ Cl- Al3+ O2-

  24. Steps for Writing Formulas of Simple Ionic Compounds - Balancing Charges • Identify each ion and its charge. • Determine the total charges needed to balance positive with negative so that there is a net zero charge. • Note the ratio of positive ions to negative ions (these will become your subscripts). • Write the formula using subscripts to indicate how many of each atom you need. REMINDER - “1” is not shown in the subscripts.

  25. Example - Formula for Ionic Compound Aluminum chloride

  26. Example - Formula for Ionic Compound Zinc Nitride

  27. Steps for Writing Formulas of Simple Ionic Compounds - Criss Cross • Write the symbols for each atom • SUPERSCRIPT the ion charges (but drop +/- signs) • Cross the ion charges (without charges) to become the subscript of the opposite atom. • Reduce if needed.

  28. Steps for Writing Formulas of Simple Ionic Compounds - Criss Cross

  29. Covalent Compound Formula Follow the instructions provided by the name • DO NOT reduce Example: sulfur trioxide one sulfur and three oxygen → SO3 Example: dichlorine monoxide two chlorine and one oxygen → Cl2O Example: dinitrogen dioxide two nitrogen and two oxygen → N2O2DO NOT reduce

  30. Multivalent Metals Multivalent metals - metals that can form on an ion in more than one way, resulting in different ions with different charges. Multi means…many. State three examples of elements that have more than one ion charge (look at your Periodic table). Cr2+ Cr3+ Fe2+ Fe3+ Cu2+ Cu+

  31. Example Iron (II) Oxide (FeO) Iron (III) Oxide (Fe2O3)

  32. Roman Numerals Roman numerals are used when naming ionic compounds that include multivalent metals.

  33. Steps Writing Formula with Multivalent Metal Ions 1. Write the metal ion first 2. The Roman numeral in the brackets indicates what the ion charge is on the metal ion 3. Write the non-metal ion charge 4. Balance the charges or crisscross method

  34. Examples Chromium (II) chloride Chromium (II) oxide Cu2+Cl- Cr2+O2- Cu2Cl1 2+ = 2- CuCl2 CrO

  35. Steps to Name Compounds that contain Multivalent Metal Ions 1. Write the metal ion first • Reverse cross to find ion charges OR • Write the non-metal ion charge and balance it to the metal to find metal ion charge • The ion charge on the metal ion → Roman numeral after metal 2. Write the non-metal with “ide” at the end

  36. Examples Reverse Cross Balance Charges Fe2O3 FeO Fe2O3 Fe O2- Fe3O2 Fe2+O2- Iron (III) oxide Iron (II) oxide

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