1 Chemical Bonding & Writing and Naming Chemical Formulas and Compounds

2 Bonding and Molecules Energy levels-where electrons are found in the electron cloud Valence electrons –outermost region of electron cloud –Maximum number is 8, except at first level only holds 2 –Octet rule-atoms share or transfer to form bonds and become stable max at 8

3 Chemical Bond Chemical bond force that holds together the atoms in a substance By losing, gaining or sharing electrons atoms become stable and will make a bond

4 Ions Atoms that have a charge By looking at the outer energy level you can tell what charge the ion has on it Written with a superscript number above Na +1, Cl -1, P -3, Mg +2

5 Oxidation Number Number we assign from the ion charge Positive or negative number Tells how many electrons will be gained, lost or shared in a bond Remember –losing electrons causes a (+ #) –gaining electrons cause a (- #)

6 Types of Bonding 1.Ionic Bond Gaining or losing electrons Usually formed by bonding between METAL and NONMETAL Force of attraction between the opposite charges of the ions 2. Covalent Bond Sharing electrons 2 NONMETALS

7 Diatomic Molecules Covalent bonds Molecule that has 2 atoms of the same element H 2, N 2, O 2, F 2 Cl 2, Br 2, I 2, At 2 Electronegativity Attraction an atom has for the shared pair of electrons in a covalent bond Need to gain 1 or 2 electrons-high ELN Need to lose 1 or 2 electrons- low ELN

8 Chemical Formulas Chemical shorthand for a compound Subscript # tells how many atoms of that element Tells what elements it contains and ratio of atoms NaCl=1 atom sodium, 1 atom chlorine H 2 O=2 atoms hydrogen, 1 atom oxygen Fe 2 O 3 =2 atoms iron, 3 atoms oxygen Ca(OH) 2 =1 calcium, 2 oxygen, 2 hydrogen

9 Independent Practice Counting Atoms

10 Writing Chemical Formulas The ratios in which compounds are formed are called their chemical formula. MgCl 2

11 Where do the subscripts come from? That one is easy – it comes from the oxidation number. Remember that the oxidation number tells us how many electrons each particular element has extra to give away or how many it needs to become happy. MgCl 2

Oxidation Number Varies When you combine atoms, you use the oxidation numbers to help you figure out the ratio. # extra / wants to get rid of the electrons # needing / wants to get find more electrons Remember the Oxidation Numbers?

13 Let’s take a look now at the rules to writing the compounds…

14 2.Criss cross the oxidation number to get the correct subscript. Mg +2 Cl -1 1.Write down the symbol and the oxidation # for each element-metal then nonmetal Mg +2 Cl Rules for Writing Ionic Compounds 3. Leave off the (+ or -) signs

15 Rules for Writing Ionic Formulas 4.Drop out the “1’s” 5.Cancel out the numbers if they are the same MgCl 2

16 Let’s look at some examples…..

17 Mg +2 O -2 MgO 22= 2’s here cancel each other out – that way 1 is shown as the subscript. Fe +3 O -2 Fe 2 O 3 23 These subscripts can’t cancel – so they just switch & lower. GROUP PRACTICE

18 Independent Practice Fill in the the chart on your paper.

19 Now that we know how to write the formulas for the compounds – let’s name them.

20 Naming Binary Ionic Compounds Binary (meaning 2 types of atoms) 1.Identify the Metal & Write the name of the metal first. Example: KBr Potassium 2. Identify the non-metal & Write the name of the nonmetal changing the ending to ide “ide.” Bromine Bromide Metal & Non-Metal

21 Independent Practice Fill in the the chart on your paper.

22 Naming Binary Covalent Compounds Non-Metal & Non-Metal Example: CO 2 1.Identify & Name the first non-metal farthest to the LEFT. 2.Write the name of the second non-metal farthest to the RIGHT and change the ending to “-ide.” Left First Carbon Right Second Oxide Carbon Oxide

23 3.Insert the correct prefix in front of the second (2 nd ) non-metal to indicate the number of atoms present. Prefixes include: 1 – mono 2 – di3 – tri 4 – tetra5 – penta6 - septa Carbonoxidedi Non-Metal & Non-Metal – Continued Carbon Oxide Question: How do you use carbon dioxide everyday? CO 2

24 Independent Practice Fill in the blanks.

25 Covalent Compounds continued If attached to H +1 it is an ACID Will not have prefixes Examples: –HCl=hydrochloric acid –H 2 SO 4 =sulfuric acid –H 3 PO 4 =phosphoric acid

26 1. Identify & Write the name of the transition metal first. Example: CuCl Copper 2. Write the name of the nonmetal changing the ending to “ide.” Chlorine Chloride 4. The first element name gets a Roman numeral after it based on the oxidation number. (I) because the oxidation of Copper is +1 in this case. Naming Binary Compounds Transition Metal & Non-Metal 3. Use your criss cross information to determine the Roman numeral because chlorine is -1 and there are no subscript numbers then copper must be +1

27 Independent Practice Fill in the blanks.

28 Special Transition Metals Some transition metals have more than one oxidation number and a special name. Fe +2 ferrousHg +1 mercurous Fe +3 ferricHg +2 mercuric Cu +1 cuprous Sn +2 stannous Cu +2 cupricSn +4 stannic

29 What are Polyatomic Ions? Polyatomic Ions are covalent bonded groups of atoms and act as a unit. They usually stay together and don’t separate. (PO 4 ) – most of the time, you see them with ( ) marks around them. We have been working with monoatomic ions. These are single elements. Na +1, N -3, Br -1

30 Polyatomic Ion & Charges You will need to recognize the name & formula of these.

31 Mg +2 PO 4 -3 Mg 3 (PO 4 ) Li +2 SO 4 -2 LiSO Note the ( ) on multiple polyatomic ions. Writing Formulas Containing Polyatomic Ions 1.Write down the symbol and the oxidation # for each element / polyatomic ion 2.Simply switch the oxidation number to get the correct subscript. Put the #s in lowest terms if necessary. (Reduce) 3. Write the formula for the compound. Cancel “2’s”

32 Independent Practice Fill in the blanks.

33 Naming Compounds w/polyatomic ions 1. Write the name of the metal first. SO 4 Example: K 2 SO 4 Potassium 2. Write the name of the polyatomic nonmetal from the chart. Sulfate

34 Naming Compounds that start w/polyatomic ion 1. Write the name of the polyatomic ion first. Example: NH 4 Cl Ammonium 2. Write the name of the nonmetal changing the ending to “ide.” Chloride

35 Independent Practice Fill in the blanks.

36 Formula Mass Calculate the formula mass for the following H 2 SO 4 KNO 4 4 K 2 SO 4 2 Ca 3 (PO 4 ) 2