Presentation on theme: "Ionic Compounds: Compounds that are made of oppositely charged ions."— Presentation transcript:
Ionic Compounds: Compounds that are made of oppositely charged ions.
Forming Ionic Compounds Elements can combine to make ionic compounds when their atoms lose or gain electrons. Any atom that has gained or lost electron(s) is called an ion and is now charged. When atoms gain an electron, they are more negative (electrons are negatively charged particles) and are called anions. When atoms lose an electron, they are more positive and are called cations. Ionic compounds are when an anion and a cation come together to form a neutral compound, which is more stable.
The loss and gain of electrons is what makes a full outer energy level. Remember, we only need to look at the outer energy level. These electrons are called valence electrons. Ionic compounds are usually composed of one metal (left side of periodic table) and one non-metal (right side). E.g. How many valence electrons does Lithium have? Do you think it will gain or lose it’s electron(s)? Why? Answer: It has 1 valence electron. It will lose it’s electron when forming an ion because it is easier to lose one than gain 7 in order to have it’s last energy level filled up.
Naming Binary Ionic Compounds There are two ways to identify a compound: By its chemical name By its chemical formula These are the IUPAC rules for naming: 1. The 1st part always identifies the positive ion (metal cation) 2. The 2nd part always identifies the negative ion (non-metal anion)
Examples: Magnesium and phosphorus make magnesium phosphide. Sodium and chlorine make: Sodium chloride Calcium and bromine make: Calcium bromide
Examples: Write the names of the following binary ionic compounds: MgBr 2 CaI 2 Al 2 O 3 KCl Magnesium bromide calcium iodide, aluminum oxide, potassium chloride.
Activity: 4-2 Text: p Use hole punches as valence electrons Step 1: Find metal on periodic table and write the symbol. Step 2: Figure out how many valence electrons it has (hint: look at the column number it is in) Step 3: record the number of valence electrons Step 4: Find non metal and write the symbol Step 5: Figure out how many valence electrons it has Step 6: record the number of valence electrons Step 7: Give the metal’s electrons to the non-metal Step 8: You may have to add extra metals or non-metals in order to fill the valence shell.
Writing the Chemical Formula You won’t always be able to use cut outs, so follow these steps for a faster way of determining the chemical formula: Step 1: identify each ion and its charge Step 2: Determine the total positive charge and total negative charge needed to equal zero. Step 3: Note the ratio of cations to anions Step 4: Use subscripts to show the ratio of ions.
Examples: Aluminum Fluoride: 1. Aluminum: Al 3+ Fluoride: F - 2. Al 3+ = 3+ F - = (-1) x 3 = 3- 3. 1 Al 3+ : 3 F - 4. AlF 3
Multivalent Metals Some metals have more than one ion charge listed in the periodic table. These elements are called multivalent metals Eg. Copper: can be a 1+ or 2+ charge. To distinguish between the two, we use Roman Numerals after the element name. Eg. Cu +1 is written Copper(I) and Cu +2 is written Copper(II)
Chemical Formula for Multivalent Metals Example: SnS 2 Step 1: Identify the metal Sn (tin) Step 2: Verify that the metal can form more than one kind of ion Sn 2+ and Sn 4+ Step 3: Determine the ratio of ions in the chem formula 1 tin : 2 sulfide Step 4: Note the charge of the anion 2-
Step 5: The positive and negative charges must balance out so the net charge is zero. Total neg. charge: 4- Total pos. charge: 4+ Step 6: Determine what charge the metal ion must have to balance the anion. 1 Sn? = 4+ Step 7: Write the name of the metal ion The name of the metal ion is tin(IV) Step 8: Write the name of the compound Tin (IV) sulfide
Examples: Cu 3 N Answer: Copper (I) nitride
Polyatomic Ions A polyatomic ion is an ion made up of more than one atom Poly = many These ions usually end in -ate. Examples: Ammonium: NH 4 + Phosphate: PO 4 3- Carbonate: CO 3 2- Sulfate: SO 4 2- Hydroxide: OH - Nitrate: NO 3 -
Chemical Formula with Polyatomic Ions Example: Aluminum carbonate Step 1: Use the periodic table and a talbe of common polyatomic ions to identify each ion and its charge: Aluminum: Al 3+ Carbonate: CO 3 2- Step 2: Determine the total positive charge and total negative charge to equal zero. Al 3+ = 2 (3+) = 6+ CO 3 2- = 3(2-) = 6- (6+) + (6-) = 0
Step 3: Note the ratios of cations to anions: 2:3 Step 4: Use the subscripts to show the ratio of ions. Place the polyatomic ion in brackets if it needs a subscript. Al 2 (CO 3 ) 3 Now, you try: Ammonium sulfate Answer: (NH 4 ) 2 SO 4 Now work on questions on page 150 #9 and 10 Page 151 # 1-8
Molecular Compounds It is a compound formed when atoms of 2 or more different elements share electrons. They are similar to ionic compounds, but instead of one element giving it’s electrons to the other, they share the electrons between the two atoms. The shared electrons form a covalent bond. Molecules can be formed by two or more of the same element OR two or more of different elements. E.g. Oxygen found in the atmosphere is O 2 Oxygen is not a compound, since it contains only one type of atom.
Activity 4-3 Use p. 154 in your text to follow the directions for activity 4-3
Naming Binary Molecular Compounds E.G. carbon dioxide Tells us 2 pieces of info: Compound is composed of carbon and oxygen Tells you the ratio of the two elements Carbon: 1 Oxygen: 2 (di) “di” is a prefix that tells you the number of atoms in that element.
Using the Prefixes Smog has a lot of molecular compounds in it, nitrogen dioxide is an example. Use the four steps to name binary molecular compounds…
Step 1: Count the # of atoms of the first element in the chemical formula Example: N 2 O 4 # of nitrogen: 2 Step 2: Write the appropriate prefix followed by the name of the element. (mono- is never used if it is the first name in the molecule) Dinitrogen Step 3: Count the # of atoms in the second element # of Oxygen:4 Step 4: Write the prefix and the element and finally the suffix (-ide) Tetroxide Final name: dinitrogen tetroxide
You try it! BrCl (used to detect mercury in water) Answer: Bromine monochloride Try page 156 #1-4
Writing Chemical Formulas for Binary Molecular Compounds Step 1: Write the chemical symbol of 1st element Example: phosphorus trichloride PP Step 2: Determine the number of atoms in 1st element # of P: 1 Step 3: Write chem. Symbol of 2nd element Cl Step 4: Determine # of atoms in 2nd element # of Cl: 3 Write formula: PCl 3