The Making of Compounds
Compounds Compounds – The combination of two or more elements.
Have new chemical and physical properties…different from each element. Most of the matter around us is in the form of compounds or mixtures of compounds.
Compounds Ex: Sodium – shiny, soft, gray metal…reacts violently with water Ex: Chlorine – greenish, yellow gas … can kill if in air. The compound of Sodium and Chlorine make SALT.
Compounds Made through CHEMICAL BONDS – attractive force that holds atoms together. Chemical Formula – The chemical shorthand for a compound. Includes the chemical symbols and the number of atoms of that element.
Compounds The goal of every atom is to be chemically stable…with 8 outer electrons. (Octet Rule) An atom will form compounds to become stable. An atom only uses its valence electrons to form compounds. Can use Dot Diagrams to show the number of electrons in the outer shell.
Dot Diagrams and Compounds
Ex: Water (H2O) Hydrogen has one valence electron Oxygen has 6 valence electrons Neither are stable…Will form a compound to become stable
Types of Chemical Bonds: Ionic Bonding
Ionic Bonds – The force of attraction between opposite charges of ions Simple definition: Atoms give up or take electrons to become stable.
Ionic Bonding Example Sodium has one valence electron
Chlorine has 7 valence electrons Sodium gives up its 1 electron to Chlorine…They both become STABLE Sodium becomes positive (gives up electron Chlorine becomes negative (takes an electron)
Types of Chemical Bonds: Covalent Bonding
Covalent Bond – A bond that forms between atoms when they SHARE electrons
Covalent Bonds (example)
CH4 is made with Carbon and Hydrogen sharing electrons. Carbon has 4 valence electrons Hydrogen has 1 valence electron Carbon bonds with 4 Hydrogen atoms to become stable…they SHARE electrons to make all parties happy
Oxidation Numbers The number of electrons that an atom will give up or take. Useful when making compounds. Oxidation numbers are known by the group an element is in Example Group 1 – Oxidation # +1 Group (handout shows oxidation numbers) Groups 3-12 have variable oxidation numbers…depends on the compound it is making.
Polyatomic Ions An ion made of two or more atoms.
These are groups of covalently bonded atoms that have either lost or gained electrons. (combination of bonds) Polyatomic Ions are often found together in nature…have own name and oxidation numbers.
Polyatomic Ions (p. 158) Put the following on your periodic chart:
Ammonium Carbonate Chlorate Hydroxide Nitrate Phosphate Sulfate
Making Compounds…Names and Formulas
Compound Formulas – made with the chemical symbol and the number of atoms used Example: H2O uses 2 Hydrogen atoms for every 1 Oxygen atom. Example: H2SO4 uses 2 Hydrogen atoms to 1 Sulfate ion
Making Compounds 1. Find Chemical Symbols
2. Find Oxidation Number for that Element 3. Write the Chemical Symbol with the Oxidation Number as a Superscript Example: Sodium and Chlorine Na+1 Cl-1
Making Compounds 4. Criss-cross the oxidation numbers…(give the number to the opposite element as a subscript) Na+1 Cl-1 To: Na-1 Cl+1 5. Drop the sign (+ / -) Na1Cl1 6. Write the compound NaCl (when the subscript is 1 it does not have to be written)
Making Compounds Practice
1. Calcium and Nitrogen 2. Magnesium and Oxygen 3. Calcium and Chlorine
Making Compounds Practice Answers:
1. Calcium and Nitrogen Ca+2 Nitrogen-3 Ca3N2 2. Magnesium and Oxygen Mg+2 O-2 Mg2O2 or MgO 3. Calcium and Chlorine Ca+2 Cl-1 CaCl2
Naming Compounds Most of the time you can name an IONIC Compound by
1. Writing the Name of the FIRST ELEMENT 2. Writing the ROOT of the SECOND ELEMENT 3. Adding –IDE to the root
Naming Compounds: Examples
CaCl2 - Calcium chloride K3P - Potassium phosphide Al2S3 - Aluminum sulfide
Naming Compounds Some of our metals have more than one ionic charge
1. We have to figure out what the ionic charge is 2. Then we must show which of the elements it is with a roman numeral
Naming Compounds: Examples
FeCl2 - Iron(II) chloride FeCl3 - Iron(III) chloride PbBr2 - Lead(II) bromide
Naming Compounds If the compound has a polyatomic ion in it:
1. Write the name of the FIRST element 2. Then find the name of the POLYATOMIC ION and write it
Naming Compounds: With Polyatomic Ions
Fe(OH)2 - Iron(II) hydroxide Ca3(PO4)2 - Calcium phosphate Na2SO4 - Sodium sulfate
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