Bonding-when atoms get it on. Ionic Compounds 9/22/2013. Chemical Formulas and Bonding

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1 Bonding-when atoms get it on Chemical Formulas and Bonding There are two types of bonds that you need to know. The first kind of bond is Ionic bond. Ionic Bond = when a positive ion is attracted to a negatively charge ion. Ionic bonds often form between metals and nonmetals. Ionic Compounds Composed entirely of positively and negatively charged ions. They are electrically neutral. Cation= paws -ative charged ion. Anion = negative charged ion. Many ionic compounds, like salt, contain repeating patterns of cations and anions forming complex crystals. 1

2 Ionic compounds tend to be brittle, have high melting points, and many dissolve in water. Lewis Dot Diagrams A way to show valence electrons. Each dot represents a valence electron. Types of Ions Write the lewis dot structures for the following: 1. Mg 2. Ar 3. Cl 4. He 5. C Monatomic Cations and anions Ions consisting of one atom with paws -ative and negative charges. Polyatomic Ions Ions consisting of 2 or more atoms. You need to memorize NH 4+ = Ammonium 2. OH - = Hydroxide 3. ClO - = Hypochlorite 4. NO - 3 = Nitrate 5. HCO - 3 = Bicarbonate 6. C 2 H 3 O - 2 = Acetate 7. SO 4 2- = Sulfate 8. CO 2-3 = Carbonate 9. PO 3-4 = Phosphate 2

3 Binary Ionic Compounds Empirical Formulas Contain the ions of two elements. To name them just write the name of the cation followed by the name of the anion. For the anion drop the last syllable (usually) and add ide on the end. Ex: The name of the Ionic compound formed when sodium and chlorine come together = Sodium Chloride. Shows the ratio of atoms in a compound 1. Place the ions next to each other. Always put the Cation on the left. Ex: Ca 2+ F 1-2. Criss-cross charges without plus and minus signs Ex: Ca 1 F 2 3. Now drop any ones, and if you have two of the same charges drop them. Ex: CaF 2 Mg 2 O 2 = MgO Note: If the compound contains a polyatomic ion parentheses are needed if there is a subscript. Ex: Calcium Hydroxide Ca(OH) 2 Write the empirical formulas 4: 1. Calcium Bromide 2. Potassium Phosphide 3. Aluminum Sulfate 4. Potassium Phosphate How about Transition Metals Naming Chemical Compounds How do you know what charge they will have? The charge must be given to you in roman numeral form. Ex: Cromium (II) Chloride = CrCl 2 Naming Ionic Compounds Name the cation first Then name the anion with an ide ending. Ex: NaCl Sodium Chloride SrI 2 Strontium Iodide 3

4 Is That It? Name the following Ionic compounds: 1. MgS 2. CsCl 2 3. K 2 O 4. NaF Nope When you are naming a compound with a transition metal, you must find the charge of the metal ion and write it as a roman numeral in parentheses. You find the charge of the metal, by looking at the charge of the anion. Because they have to equal out Covalent Bonds Ex:: CrO = Cromium (II) Oxide Cr 2 O = Cromium (I) Oxide CrO 2 = Cromium (IV) Oxide Name the following: TiNO 3, NH 4 Br, Co(OH) 2 CuSO 4, Cu 2 O, Fe 2 S 3 A covalent bond occurs when atoms share a pair of electrons. Often form between nonmetals. Atoms bond covalently to satisfy the octet rule Molecule = a group of atoms held together by covalent bonds. Molecular formula- tells how many of each atom is an a molecule. How is this different from an empirical formula? Molecular formula: C 6 H 12 O 6 Empirical formula: CH 2 O Structural formula: a formula that specifies which atom is bonded to each other in a molecule. 4

5 Lewis dot structures Sometimes Lines are used to Show bonds 5

6 Multiple Bonds Double bonds-a bond with two pairs of shared electrons (Denoted by two lines) Triple Bonds a bond with three pairs of electrons (Denoted by three lines) Its very strong 6

7 Naming Molecular Compounds Same as naming ionic compounds, except you have to use prefixes to indicate the number of atoms in the molecule The most electronegative atom is written last and contains the suffix -ide Ex: C 2 O 2 Dicarbon Dioxide Exceptions The prefix mono- is usually not written with the first word of a compounds name Ex: CO 2 is not Monocarbon Dioxide. Prefixes are sometimes shortened to make names easier to say. Ex: CO is called carbon monoxide not Carbon monooxide More exceptions Chemists use common names for some compounds Ex: H 2 O is called water, not dihydrogen monoxide NH 3 is called ammonia 7