Chemical Bonds Unit 6 Chapter 6 IONIC COVALENT METALLIC

I. Why do atoms bond? A. Atoms bond in order to become stable B. Electron configurations of the noble gases are stable. 1. Helium is stable with 2 valence e All others are stable with 8 valence e -. C. Atoms of unstable electron configurations will gain, lose, or share electrons to become stable like a noble gas.

not stable stable not stablestable

II. Electron Dot Notation A. Only valence electrons are used in bonding B. Electron dot notation highlights the valence electrons AlCaF Cs

Representative Group Valence Electrons

How to draw the electron dot notation of an atom: Step 1: Write the chemical symbol Step 2: Imagine a box around it Step 3: Draw a dot for each valence electron Dots only go on the SIDES of the box Rule: One dot per side before you double up As YES!

Now you try some. LiClNe SrCMg PbN I

What would happen if sodium and chlorine bump into each other? An electron would transfer from the Na atom to the Cl atom so that each atom would become a stable ion. Net charge +1 Net charge -1

III. Ionic Bonds A. Metal – Nonmetal B. Electrons are transferred from the metal to the nonmetal C. Ions are produced D. Ion attraction makes the bond (+)(-)Na +1 Cl -1

E. A Crystal is formed

Ca I Let’s Practice! K Br Before bondingAfter BondingChemical Formula K Br I I CaI Ion net charge = zero!

A. Nonmetal – Nonmetal B. Electrons are shared C. Molecules are produced D. Sharing makes the bond (tug-o-war) F F or F F IV. Covalent Bonds 2 Shared electrons

E. Can have double and triple bonds Double: O O or O O 4 Shared electrons Triple: N N or N N 6 Shared electrons (a stronger bond) (the strongest bond)

F. Diatomic elements are formed as follows: H 2 N 2 O 2 F 2 Cl 2 Br 2 I 2 BrINClHOF

Let’s Practice! Before bondingAfter BondingChemical Formula C H H H H H H C H H CH 4 All atoms are stable!

Now you try some. 1. N and F 2. H and O 3. Diagram the molecule C 2 H 6 O

Answer to #1: N F F F F F F N F NF 3 beforeafterformula

Answer to #2: H O H H O H H2OH2O beforeafterformula

Answer to #3: C2H6OC2H6O OHC H H H H C H C H H H O H C H H or

A. metal – metal B. Electrons are pushed from atom to atom. C. Electrons are free to move among the metal atoms allowing metals to conduct electricity. (see picture below) D. A mixture of metals is called an Alloy. V. Metallic Bonds

A. Formula Writing 1. Cation first, anion second Ca +2 Cl Net charge must equal zero Ca +2 Cl -1 Cl -1 = zero (It takes 2 chloride ions to stabilize the Ca) 3. Write the formula: CaCl 2 VI. Ionic Binary Chemicals

B. Naming 1. The metal ion has the same name as the metal atom. Ca +2 is named calcium K +1 is named potassium 2. Some metals form more than one ion. These metals require a roman numeral after their name to indicate which ion is in the chemical formula. Fe +2 is named iron (II) Fe +3 is named iron (III)

NO roman numeral in the name, element only produces one common ion. Roman numeral is necessary, element contains more than one common ion.

3. The nonmetal ion will end with the suffix -ide. Examples: S -2 is named sulfide F -1 is named fluoride O -2 is named oxide P -3 is named phosphide N -3 is named nitride

A. Formula Writing 1. Follow the ionic rules. 2. Ternary chemicals contain a polyatomic ion. polyatomic ion- a group of covalently bonded atoms that act as a single ion examples: CO 3 -2 NH 4 +1 VII. Ionic Ternary Chemicals

3. RULE : If more than one polyatomic ion is needed to write the chemical formula use parenthesis. example: Ca +2 NO 3 -1 NO 3 -1 CaNO 32 zero net charge Ca(NO 3 ) 2 YES, two NO 3 -1 ions! (looks like we have 32 oxygen atoms)

B. Naming 1. Follow the ionic rules. 2. Examples: Al(OH) 3 is named aluminum hydroxide Cu(NO 3 ) 2 is named copper (II) nitrate K 2 CO 3 is named potassium carbonate

A. Greek prefixes are used to identify the number of each element in a covalent compound. mono = 1 di = 2 tri = 3 tetra = 4 penta = 5 hexa = 6 hepta = 7 VIII. Covalent Chemicals

B. Rule: mono- is never used for the first element in the compound. C. Sometimes the last letter of the prefix is dropped if the name of the element starts with a vowel. D. Examples: CO 2 is named carbon dioxide CO is named carbon monoxide dinitrogen monoxide is written as N 2 O