IONIC BONDING. Belton High School

Transcription

1 IONIC BONDING Belton High School

2 Chemical Bond Definition a mutual electrical attraction between the nuclei and valence electrons of different atoms Valence electrons are electrons available to form a chemical bond. These electrons are in the outermost s and p orbital

3 Making Ionic Compounds Why do atoms bond? Independent atoms are at a relatively high potential energy. Bonding allows atoms to become more stable

4 There are two types of Chemical COVALENT Bonds Occurs when electrons are shared between two non-metals We will study these after break IONIC Occurs between METALS and NON METALS

5 Formation of Positive Ions Metals LOSE electrons and form POSITIVE (+) ions. Positively charged ions are called cations Metals (main group elements, s & p blocks) Number electrons lost = valence electrons Ion charge = number of electrons lost Transition metals (d-block) are multivalent Use the chart to determine the charge

6 Formation of Negative Ions Nonmetals GAIN electrons and form NEGATIVE (-) ions. Negatively charged ions are called anions Number of electrons gained = 8 valence electrons Ion charge = number of electrons gained

7 Calculating the number of Valence Electrons Simple, look at periodic table! On your periodic table, write the # of valence electrons for each main group

8 Practice Problems How many valence electrons are in the following elements? Mg 2 val. electrons F 7 val. electrons Na 1 val. electron Al 3 val. electrons

9 To keep track of valence electrons, we use an electron dot structures Electron dot diagrams represent VALENCE electrons. 1) Write the symbol of the element. 2) Draw dots to represent valence electrons

10 Practice Problems Draw the electron dot structures for the following atoms: Carbon Neon Barium Silicon

11 Noble Gases Noble gas are extremely stable due to a completely filled s and p orbital Noble gases have 8 val. Electrons (except He) All the other elements want to be like a Noble Gas Octet Rule: Atoms lose, gain, or share to reach an octet (8) of valence electrons.

12 Determining the Charge of Ions Remember Ions are positively or negatively charged atoms Ions have either gained or lost electrons Start with drawing electron dot structure, then determine how many electrons need to be gained or lost to achieve an octet Example) Fluorine

13 Determining the Charge of Ions Refer to Periodic Table!!

14 Practice Problems Determine the Charge of the following Ions Nitrogen Lithium Radium Chlorine

15 Practice Problems Determine the Charge of the following Ions Nitrogen -3 Lithium +1 Radium +2 Chlorine -1

16 Making Ionic Compounds An ionic compound is between a cation and an anion. The positive and negative charges must balance one another. The total overall charge must always equal zero (0) Why do atoms bond? Independent atoms are at a relatively high potential energy. Bonding allows atoms to become more stable

17 Electron Dot Structure for Ionic Compounds We will use arrows to show the movement of electrons for ionic compounds. The electrons always go from Cations (metal) to Anions (non-metal) Therefore, your arrow always points to the nonmetal Example) Na and Cl

18 1). Ionic bond electron from Na is transferred to Cl, this causes a charge imbalance in each atom. The Na becomes (Na+) and the Cl becomes (Cl-), charged particles or ions.

19 Electron Dot Structure of Electron Pushing Model

20 Writing Formulas for Ionic Compounds Step One Write the ions for each atom involved in the bond. Step Two Balance the charges to make the sum equal zero Example) Potassium and Oxygen 1) K +1 and O -2 2) K 2 O Subscript tells you the number of atoms No subscript is an understood ONE K + K + O 2-

21 Writing Formulas Lithium and Oxygen Li + Li + O 2- Hydrogen and Fluorine HF H + F - Metal/Cation Li 2 O Non Metal/Anion Al 3+ O 2- Aluminum and Oxygen Al 2 O 3 Al 3+ O 2- O 2-

22 Putting Ions Together Criss Cross Method Na + + Cl - = Ca +2 + Cl - = Ca +2 + O -2 = Ca +2 + N -3 = You try these! Li + + Br - = Mg +2 + F - = Al +3 + I - = Sr +2 + P -3 =

23 Putting Ions Together Criss Cross Method Na + + Cl - = NaCl Ca +2 + Cl - = CaCl 2 Ca +2 + O -2 = CaO Ca +2 + N -3 = Ca 3 N 2 You try these! Li + + Br - = LiBr Mg +2 + F - = MgF 2 Al +3 + I - = AlI 3 Sr +2 + P -3 = Sr 3 P 2

24 Naming Ionic Compounds There are three types of ionic compounds and each one has a different naming system Binary Compounds 2 ions bonded together Multivalent Compounds transition metal bonded to a non-metal Polyatomic Compounds more than 2 ions bonded together Refer to your table of common polyatomic Ions for naming

25 Binary Ionic Compounds Remember in writing the formula, put cation first and anion second Rules for naming: 1) Name the first element 2) Change the ending of the second element to ide For example) CaCl 2 = calcium chloride MgS = magnesium sulfide

26 Practice Problems Name the following compounds 1) LiI 2) BaF 2 3) KCl 4) CaBr 2

27 Practice Problems Name the following compounds 1) LiI Lithium Iodide 2) BaF 2 Barium Fluoride 3) KCl Potassium Chloride 4) CaBr 2 Calcium Bromide

28 Practice Problems Give the following formulas for the binary compounds 1) aluminum sulfide 2) potassium oxide 3) Aluminum fluoride 4) barium oxide

29 Practice Problems Give the following formulas for the binary compounds 1) aluminum sulfide Al 2 S 3 2) potassium oxide K 2 O 3) Aluminum fluoride AlF 3 4) barium oxide BaO

30 Naming Multivalent Compounds Transition Metals (d-block) can have multiple valence electron numbers Therefore you must specify the charge when writing the name. Rules to naming: 1) Name the first element 2) Show the charge of the ion with Roman numerals 3) Change the ending of the second element to ide Example) Cu 2 S = copper (I) sulfide

31 Practice Problems Write the name of the following multivalent compounds 1) Lead (II) bromide 2) Manganese (II) oxide 3) Iron (III) sulfide 4) Nickel (IV) bromide

32 Practice Problems Write the name of the following multivalent compounds 1) Lead (II) bromide PbBr 2 2) Manganese (II) oxide MnO 3) Iron (III) sulfide Fe 2 S 3 4) Nickel (IV) bromide NiBr 4

33 Practice Problems Write the formula for the following compounds 1) iron (II) sulfide 2) cobalt (III) sulfide 3) manganese (II) phosphide 4) chromium (III) flouride

34 Practice Problems Write the formula for the following compounds 1) iron (II) sulfide FeS 2) cobalt (III) sulfide Co 2 S 3 3) manganese (II) phosphide Mn 3 P 2 4) chromium (III) flouride CrF 3

35 Naming Ionic Compounds with Polyatomic Ions Polyatomic Ions contain more than one element There is a list of common polyatomic ions with their names and formulas *** Always treat polyatomic ions as if they are one element. They act as a group. Naming Rules: Name the first element Name the polyatomic ion (DON T change ending to ide)

36 Practice Problems Name the following compounds 1) LiNO 3 2) Ba(OH) 2 3) AlPO 4 4) Be(ClO 2 ) 2

37 Practice Problems Name the following compounds 1) LiNO 3 Lithium nitrate 2) Ba(OH) 2 Barium hydroxide 3) AlPO 4 Aluminum phosphate 4) Be(ClO 2 ) 2 Beryllium chlorite

38 Practice Problems Give the following formulas for the compound 1) silver phosphate Ag 3 PO 4 2) calcium hydroxide Ca(OH) 2 3) aluminum nitrate Al(NO 3 ) 3 4) lead (II) carbonate PbCO 3

39 Practice Problems Give the following formulas for the compound 1) silver phosphate 2) calcium hydroxide 3) aluminum nitrate 4) lead (II) carbonate

40 Oxidation Numbers Definition A number that indicates the general distribution of electrons among the bonded atoms Oxidation number of a neutral element is ZERO In a compound, the sum of all atoms oxidation numbers equals ZERO For Ionic compounds, the oxidation number equals the ion charge

41 Oxidation Number Practice Determine the oxidation number for. ZERO 1) Mg = 2) In MgO, the oxidation number of the Mg ion is +2 and Oxygen ion is. -2 3) In Ni (III) N, the oxidation number of the Ni ion is +3 and the nitrogen ion is. -3 *** Notice the sum of atoms is always ZERO for neutral compounds.

42 Flow Chart for Naming Does the compound have more than 2 elements? You have a binary compound. Is your metal multivalent? You have a polyatomic Compound. Is your metal multivalent? NO YES NO YES Naming: 1) Name cation 2) Name anion changing ending to -ide Naming: 1) Name cation 2) In roman numerals put charge of metal 3) Name anion changing ending to -ide Naming: 1) Name metal 2) Name polyatomic ion Or 1) Name polyatomic 2) Name anion changing ending to -ide Naming: 1) Name metal 2) In roman numerials put charge of metal 3) Name polyatomic ion