Physical Science CHEMISTRY REVIEW

Why do atoms Bond?  Brainstorm:  What is the Octet Rule ?

Types of Bonds  Colvalent:  Ionic:

Writing Formulas  When writing a formula it is important to remember that every compound has a charge of zero, unless stated otherwise  This means that the charge of the anions (negative) and cations (positive) will add up to zero

 Binary compounds are made of two monatomic ions  Monatomic ion are ions that contain only one type of element (i.e you can find it on the periodic table)  Ex Na +, H +, O -2, N -3  Charges are found on the periodic table  Example of binary compounds  NaCl, CaCl, KF, Li 2 O

Polyatomic Compounds  These compounds contain polyatomic ions  A polyatomic ion is made up of more than one ion but it acts just like monatomic ions do  Charges and names of polyatomic ions can be found on the back of your periodic tables  **note** polyatomic ions are ALWAYS anions (negative)  Examples: NO 3 - CO 3 - SO 4 -

Writing Formulas  Find how many of each ion that you need to make the overall charge equal zero  Hint: use the charges to determine how many atoms you need  Na +1 C -4  Ca +2 C -4  Ca +1 (PO 4 ) -3  K O  Na (PO 4 )

Naming rules  Covalent naming: 1. Always write the least electronegative element first 2. The more electronegative element is then written, but to it the suffix –ide is added to it  Ex oxygen- oxide  fluorine- fluoride  nitrogen- nitride 3. We now find the problem of distinguishing between compounds with more than one formula (ex CO, CO2)  To prevent this from occurring we add a greek prefix to the element names

1- mono6- hexa 2- di7- hepta 3- tri8- octa 4- tetra9-nona 5- penta10- deca Note: when an element’s name begins with a vowel, the vowel at the end of the prefix is dropped; Example: monoxide vs monooxide

You Try  NF 3  N 2 O 4  OF 2

Ionic Bonds Rules 1. Separate the compound into cations and anions  Cations- the name will stay the same  Ex. Ca +2 stays as calcium  Anions- the suffix –ide is added to the element name  Ex. Br – becomes bromide Ion 2. To name the ionic compound add the names of the ions together  Ex. CaBr2  calcium + bromide = calcium bromide

Examples:  K 2 O  CaF 2  BaO

Polyvalent metals 3. Some metals can have more than one charge therefore we have to distinguish which charge the metal has  FeO- looking at the periodic table Fe could have a +2 or a +3 charge  To find it’s charge, look at the charge on the anion (and the number of these charges)  Ex. FeO has one anion with a -2 charge, therefore the Fe must balance that charge and have a +2 charge (the total anion and the total cation charges must be equal)

4. Now that the charge on Fe is known as +2, we have to show that in it’s name  We do this by adding a roman numeral to the cation  FeO- Fe has a +2 charge therefore the roman numeral II is added after iron  FeO- iron (II) oxide 1I4IV 2II5V 3III6VI

 Note only metals with more than one charge have to have the roman numeral added to it  Ex. Gallium (Ga) only has one charge; which is +3, therefore we don’t have to add the roman numeral to it’s name  Use the periodic table to determine which metals can have more than one charge  In pairs look at the periodic table and list those metals that can have more than one charge

Balancing Equations 1. Write down the unbalanced equation 2. Draw boxes around each chemical formula- never ever change anything inside the boxes 3. Make an element inventory- write down how many of each element you have 4. Write numbers in front of the boxes to try to get the same number of atoms on each side of the equation

Some of Mrs. Lalonde`s Helpful Hints for balancing equations  Save H for next to last, and O until last.  IF everything balances except for O, double all the coefficients and try again.  (Shortcut) Polyatomic ions that appear on both sides of the equation should be balanced as independent units

 Zn + HCl ---> ZnCl 2 + H 2  KClO 3 ---> KCl + O 2

 Zn + HCl ---> ZnCl 2 + H 2  S 8 + F 2 ---> SF 6

 Fe + O 2 ---> Fe 2 O 3  C 2 H 6 + O 2 ---> CO 2 + H 2 O