1. Unit B Chemical Reactions Gizmos

2. Copyright © 2010 Pearson Canada Inc. B - 1 4.2: Ionic and Molecular Compounds Compounds are formed when atoms of different elements combine in a process involving the transfer of electrons from one atom to another. For example, when atoms of sodium metal combine with atoms of chlorine to form sodium chloride,

3. Copyright © 2010 Pearson Canada Inc. B - 2 Bohr Diagrams Showing Transfer of Electrons

4. Copyright © 2010 Pearson Canada Inc. B - 3 Sodium metal and chlorine gas react to form the ionic compound sodium chloride (NaCl)

5. Copyright © 2010 Pearson Canada Inc. B - 4 Properties of ionic compounds most are hard, brittle solids that can be crushed. They form crystals that have an alternating arrangement of positively charged ions and negatively charged ions. Every ion is attracted to every other in the crystal resulting in high melting points. sodium chloride melts at 800ºC. ionic compound dissolves in water, Solutions of ionic compounds conduct electricity. The are called electrolytes

6. Copyright © 2010 Pearson Canada Inc. B - 5 Structure of Crystals of NaCI

7. Copyright © 2010 Pearson Canada Inc. B - 6 Ionic Symbols and Names ElementIon ChargeSymbol sodium1+1+ Na + calcium2+2+ Ca 2+ aluminum3+3+ Al 3+ fluorine1–1– F – (Fluoride) oxygen2–2– O 2– (oxide) lead2+4+2+4+ Pb 2+ lead(II) Pb 4+ lead(IV)

8. Copyright © 2010 Pearson Canada Inc. B - 7 Ion Symbols and Names Write the symbol of the element and show the ion charge as a superscript. For example, the symbol of a calcium ion is Ca 2+ When an element can form only one type of ion, the ion has the same name as the element. A multivalent element is an element that can form an ion in more than one way. Many metal elements are multivalent. For example, Cu + is named copper (I), which is read as “copper one.” Similarly, Cu 2+ is named copper (II), which is read “copper two.”

9. Copyright © 2010 Pearson Canada Inc. B - 8 Compounds Containing Multivalent Elements Multivalent element always contains a Roman numeral to indicate its charge. nickel(II) sulphide indicates that the Ni 2+ ion forms the compound. nickel(III) bromide indicates that the Ni 3+ in the compound

10. Copyright © 2010 Pearson Canada Inc. B - 9 Naming Binary Ionic Compounds 1.Name the metal ion first, which is same as the element name. 2. Name the non-metal ion second. When a non-metal becomes a negative ion, the ending of its name changes to “ide.” 3. Name the ionic compound by combining the ion names. 4. The name of KBr is, therefore, potassium bromide. Copy Table 4.6 pg 159

11. Copyright © 2010 Pearson Canada Inc. B - 10 Steps for writing Ionic Compounds Identify the ions and their charges. Determine the number of each ion needed to balance the charges. Note the ratio of positive to negative ions, and write the formula. Write the chemical formula, using subscripts if needed.

12. Copyright © 2010 Pearson Canada Inc. B - 11 Examples calcium bromide magnesium nitride Copper (II) oxide calcium: Ca 2+ bromide: Br – magnesium: Mg 2+ nitride: N 3– copper (II): Cu 2+ oxide: O 2– Ca 2+ Br – Mg 2+ Mg 2+ Mg 2+ N 3– N 3– Cu 2+ O 2– 1 Ca 2+ to 2 Br - 3 Mg 2+ to 2 N 3- 1 Cu 2+ to 1O 2- CaBr 2 Mg 3 N 2 CuO

13. Copyright © 2010 Pearson Canada Inc. B - 12 Practice- binary ionic compounds Write the formula of the following: Copper (II) chloride Sodium carbide Barium fluoride Cesium sulfide Aluminum nitride

14. Copyright © 2010 Pearson Canada Inc. B - 13 Polyatomic Ions A polyatomic ion is a group of atoms, usually of different elements, that act as a single ion. Sulphur and four atoms of oxygen form the polyatomic ion called sulphate, or SO 4 2–. the sulphate ion can combine with the lead (II) ion to form PbSO 4. Pb 2+ + SO 4 2– PbSO 4 Copy Table 4.7 & 4.8 pg 161

15. Copyright © 2010 Pearson Canada Inc. B - 14 Common Polyatomic Ions. ammoniumNH 4 + carbonateCO 3 2- hydrogen carbonate (bicarbonate) HCO 3 - hydroxideOH - nitrateNO 3 - nitrite NO2NO 2 - sulphateSO 4 2-

16. Copyright © 2010 Pearson Canada Inc. B - 15 Formulas for Compounds with Polyatomic Ions rules are similar to the rules for other ionic compounds the positive and negative charges in an ionic compound must be equal. brackets may be used to show the ratio of ions. For example, in Cr(HCO 3 ) 3,

17. Copyright © 2010 Pearson Canada Inc. B - 16 Examples of Polyatomic Ions in Formulas Namecalcium carbonate ammonium sulphide Iron (lll) hydroxide ammonium phosphate IonsCa 2+ CO 3 2– NH 4 + S 2– Fe 3+ OH – NH 4 + PO 4 3– Ratio of Ions Ca 2+ CO 3 2– (1:1) NH 4 + S 2– (2:1) Fe 3+ OH – OH – OH – ( 1: 3) NH 4 + NH 4 + PO 4 3– (3:1) FormulaCaCO 3 (NH 4 ) 2 SFe(OH) 3 (NH 4 ) 3 PO 4

18. Copyright © 2010 Pearson Canada Inc. B - 17 Molecular Elements A molecule is a combination of two or more atoms held together by covalent bonds. A covalent bond is a connection, between atoms of non-metals, in which atoms share electrons. A pair of electrons forms a single; two pairs forms a double bond. Molecular elements for diatomic molecules.

19. Copyright © 2010 Pearson Canada Inc. B - 18 Common Diatomic Molecules ElementFormula bromineBr 2 chlorineCl 2 fluorineF2F2 hydrogenH2H2 iodineI2I2 nitrogenN2N2 oxygenO2O2

20. Copyright © 2010 Pearson Canada Inc. B - 19 Sharing of Electrons in a Covalent Bond

21. Copyright © 2010 Pearson Canada Inc. B - 20 Molecular Compounds molecular compound is formed when atoms of two or more different non-metals combine Prefixes Used in Naming Molecules

22. Copyright © 2010 Pearson Canada Inc. B - 21 Model of Glucose Molecule

23. Copyright © 2010 Pearson Canada Inc. B - 22 Bohr Diagrams of Water Molecules

24. Copyright © 2010 Pearson Canada Inc. B - 23 Bohr Diagram of Hydrogen Gas, H 2

25. Copyright © 2010 Pearson Canada Inc. B - 24 Properties of Molecular Compounds They are often soft. If they dissolve in water, they form solutions that do not conduct electricity. They have low melting points. For example, white table sugar can be melted on a stove. The chemical name for table sugar is sucrose, and its formula is C 12 H 22 O 11.

26. Copyright © 2010 Pearson Canada Inc. B - 25 Naming Binary Molecular Compounds Prefixes are used in naming molecular compounds Number of Atoms Prefix 1Mono- 2di- 3tri- 4tetra- 5penta- 6hexa-

27. Copyright © 2010 Pearson Canada Inc. B - 26 Naming Binary Molecular Compounds Steps Examples N 2 O PBr 3 1.Name the first element. nitrogen phosphorus 2. Name the second element, using “-ide”. oxide bromide 3. Add prefixes to indicate the number of each atom. dinitrogen monoxidephosphorus tribromide

28. Copyright © 2010 Pearson Canada Inc. B - 27 Review Questions Naming compounds video