Ionic Bonding Science 10 1

Keeping Track of Electrons The electrons responsible for the chemical properties of atoms are those in the outer energy level. Valence electrons – The electrons in the outer energy level (in valence shell). Kernel (core) electrons -those in the energy levels below the valence shell. 2

Keeping Track of Electrons Atoms in the same column Have the same number of outer electrons (valence electrons). Easily found by looking up the group number on the periodic table. Group 2 - Be, Mg, Ca,.- 2 valence electrons The last digit in the representative group number gives the number of valence electrons 3

Electron Dot diagrams (Lewis Structure) A way of keeping track of valence electrons. How to write them Write the symbol. Put one dot for each valence electron Don’t pair up until they have to X 4

The Electron Dot diagram for Nitrogen l Nitrogen has 5 valence electrons. l First we write the symbol. N l Then add 1 electron at a time to each side. l Until they are forced to pair up. 5

Write the electron dot diagram for Na Mg C O F Ne He 6

Electron Configurations for Cations Metals lose electrons to attain noble gas configuration (Born losers). They make cations (positive ions). If we look at electron configuration it makes sense. Na 2, 8, valence electron Na + 2, 8 -noble gas configuration (Ne) 7

Electron Dots For Cations Metals will have very few valence electrons Ca Calcium has two valence electrons (Group 2) 8

Electron Dots For Cations Metals will have very few valence electrons These will come off Ca 9

Electron Dots For Cations Metals will have very few valence electrons These will come off Forming cations (positive ions) Ca 2+ Calcium has lost two valence electrons 10

Electron Configurations for Anions Nonmetals gain electrons to attain noble gas configuration. They make anions (negative ions). If we look at electron configuration it makes sense. S 2, 8, valence electrons S 2- 2, 8, 8 -noble gas configuration (Ar). 11

Electron Dots For Anions Nonmetals will have many valence electrons. They will gain electrons to fill outer shell. P P 3- 12

Stable Electron Configurations All atoms react to achieve noble gas configuration. Noble gases have 8 valence electrons. Also called the octet rule. Ar 13

Ionic Bonding - the basics Metals form positive ions. Non-metals form negative ions. Anions and cations are held together by opposite charges. Ionic compounds are called salts. The bond is formed through the transfer of electrons. (From metals to nonmetals.) Electrons are transferred to achieve noble gas configuration. The valence electrons determine the formula. (Simplest ratio is called the formula unit.) 14

Ionic Bonding NaCl 15

Ionic Bonding Na + Cl - Na lost 1 electron to form 1 + cation Cl gains 1 electron to form a 1 - anion The + and – attract (force of attraction is called an ionic bond) holds the ions together. The ratio is 1:1 so the formula is NaCl 16

Counting Electrons During the formation of an ionic compound the total number of electrons lost (by metals in forming cations) must equal the total number of electrons gained (by non-metals in forming anions). Ca Group 2 loses 2 e - P Group 15 (5A) gains 3e - To keep totals equal a LCM of 6 is used. Therefore:3 x Ca = 3 x 2 + = x P = 2 x 3 - = lost (+6) = 6 gained (6-) Charges cancel. 17

Ionic Bonding All the electrons must be accounted for, total lost = total gained! CaP 18

Ionic Bonding CaP 19

Ionic Bonding Ca 2+ P 20

Ionic Bonding Ca 2+ P Ca 21

Ionic Bonding Ca 2+ P 3- Ca 22

Ionic Bonding Ca 2+ P 3- Ca P 23

Ionic Bonding Ca 2+ P 3- Ca 2+ P 24

Ionic Bonding Ca 2+ P 3- Ca 2+ P Ca 25

Ionic Bonding Ca 2+ P 3- Ca 2+ P Ca 26

Ionic Bonding Ca 2+ P 3- Ca 2+ P 3- Ca 2+ 27

Ionic Bonding Ca 3 P 2 Formula Unit The Ca to P ratio is 3:2 so: 3 x 2+ = 6+2 x 3 – = 6 – – = 0 (# e – lost = # e – gained) 28

Most Transition Metals do not have form cations of one fixed charge, they tend to have variable charges. 29

Properties of Ionic compounds: High melting points. Conduct electricity when dissolved in water or in molten state. They do not conduct electricity in solid state because the electrons are not able to move. Ionic substances tend to be electrolytes - a substance that dissolves in water to produce a solution that will conduct electricity. Solid are a crystal lattice. 30

Some common binary ionic compounds: NaCl – table salt KCl – potash AlCl 3 antiperspirant CaCl 2 – road salt 31

Naming fixed binary ionic compounds Ionic compounds are formed between metals and non-metals. When naming them, we name the Cation (metal) first, then we name the anion (non- metal) last- changing the last part of the name of the element to “ide”. Ex: chlorine – chloride oxygen – oxide nitrogen - nitride 32

Formula Writing and Naming: Fixed Binary ionic compounds Formula: write the cation first and anion last. Name: Name the cation first (use the element name) Name the anion but change the ending to “ide” So, Formula: KCl Name: potassium chloride 33

Example- Show the formation of the compound formed between Na and O. Formula Na 2 O Name: sodium oxide 34

Show the formation of CaCl 2. Name: calcium chloride 35

Show the formation of the following fixed binary ionic compounds using electron-dot structures (Lewis structures). Also write the names of the compounds. a) K 3 P b) NaF c) Al 2 O 3 Predict the formula and name the compounds formed when the following elements react. a) K and F b) Li and O c) Mg and P 36

Write the formula and the name for the ionic compound formed from each of the following ions. a) Ca 2+ and Cl - b) Al 3+ and N 3- c) Be 2+ and O 2- d) Be 2+ and N 3- e) K + and S 2- 37

Practice: Name the following binary ionic compounds: A) MgO B) Al 2 S C) K 3 N D) ZnF 2 E) CaCl 2 F) LiCl G) CsF H) NaBr I) BaF 2 J) HCl Magnesium oxide Aluminum sulfide Potassium nitride zinc fluoride calcium chloride Lithium chloride Cesium fluoride Sodium bromide Barium bromide Hydrogen chloride 38

What about those ones in the “middle”? Metals, so they form positive ions (cations) They can form different ions (variable charge) eg, Fe 2+, Fe 3+ 39

Examples…. 40

Naming variable binary ionic compounds Ionic compounds formed between metals with variable charge and non-metals. When naming them, we name the metal first and state the charge in Roman numerals in brackets, then we name the non-metal last- changing the last part of the name of the element to “ide”. Roman numerals: 1 – I4 – IV 7 – VII10 – X 2 – II 5 – V 8 – VIII 3 – III 6 – VI 9 – IX 41

Ionic compounds with transition metals: FeCl 3 Fe 3+ 3Cl 1- ClFeCl FeCl 3 Cl iron(III) chloride Cu 2 S CuSCu2Cu 1+ S 2- copper(I) sulfide 42

Write the formulas for the following compounds. a)copper(I) oxide b)lead(IV) bromide c)iron(III) sulfide d)nickel(III) fluoride e)manganese(IV) sulfide Write the names of the following compounds.(Use the anion to calculate the charge of the cation.) a)FeCl 2 b)FeO c)Cu 2 O d)PbO 2 43

Polyatomic ions… ions made up of 2 or more elements. 44

Ionic compounds with polyatomic ions… NH 4 1+ and S 2- NH 4 1+ S 2- NH 4 1+ Charges cancel 2NH 4 1+ S 2- (NH 4 ) 2 S ammonium sulfide 45

Write the formula for the following ionic compounds a) Ca 2+ & NO 3 1- b) Na 1+ & OH 1- c) K 1+ & SO 4 2- d) Ba 2+ & PO 4 3- e) Li 1+ & HCO

Naming Ionic Compounds with polyatomic ions Name the cation: 1) fixed name the element 2) variable element name followed by (roman numeral) 3) name the positive polyatomic (only for NH 4 1+ ) then the anion Name the negative polyatomic ion Write the name for the ionic compounds from the previous slide. 47