These models are easy to draw – if you follow the steps! What are Bohr Models? Neils Bohr devised a method for drawing models to represent the atoms nucleus and their electron arrangement because the atoms are too small to see. These models are easy to draw – if you follow the steps!

F Drawing Bohr Models 9 Step 1: Determine the number of protons, electrons and neutrons for each atom’s element. Fluorine = F F 18.98 Fluorine 9 (Atomic Number) #Protons = 9 (Atomic Number) #Electrons = 9 # Neutrons = atomic mass – atomic # # Neutrons = 19 – 9=10

Drawing Bohr Models - Continued Step 2: Draw a nucleus inserting the # of protons and # of neutrons that are inside. # Electrons = 9 # Protons = 9 # Neutrons = 10 Fluorine = F N = P = 10 9

Drawing Bohr Models - Continued Step 3: Determine the number of electron rings to draw around the nucleus by what row it is in on the Periodic Table. # of rings = row number Fluorine is in row #2 so, I need to draw 2 rings around the nucleus. N = P = 10 9

Drawing Bohr Models - Continued Step 4: Place the electrons on the correct energy ring – filling each to capacity. Energy Levels are Identified as: 3 4 N = P = 10 9 1st Level –holds 2e- 2nd Level –holds 8e- 5 2 1 3rd Level –holds 8e- 6 9 Remember we need to have 9 electrons total for fluorine! 8 7

Complete Bohr Model P = 9 N = 10 Fluorine = F # Protons = 9 2 3 4 5 6 7 8 # Protons = 9 # Electrons = 9 # Neutrons = 10 2 Max # of Electrons Energy Level 8 1 3

Happy / Stable Elements Elements that have a full outer ring of electrons are called “happy” atoms. 2 Max # of Electrons Energy Level 8 1 3 Meaning that – that ring can’t hold any more electrons. Page Down: In making a diagram of an element scientists used to use a model called the Bohr Model. Although it does not completely describe the structure of an atom, it is a useful tool for understanding the interactions of matter. First you would write down the # of protons and neutrons the atom has. Page Down: First energy level - can hold up to 2 electrons. Page down Page Down: Second energy level - can hold up to 8 electrons. Page Down: Because the atoms are spinning around the nucleus it is important to put the out of each other’s path. The first two are paired. The next three are distributed around the energy level one at a time. The next three are paired with the previous three. Teacher Note: The rationale for teaching this is to help them understand the Lewis Dot diagrams later. Page Down: Third energy level - Similar to the 2nd level… however in reality the students will learn more about this level in chemistry. Page down. Make sure that the students have copied this slide. So, if the 2nd ring has 7 electrons in its outer ring – it is still hungry for the 8th electron – needing it to be “happy.”

Happy / Stable Elements The last ring or outer shell of the atom is called the . . . Energy Level Remember the # of rings that you drew in the Bohr model is equal to the Row number that the element is in on the Periodic Table. 16 S 32.07 17 Cl 35.45 18 Ar 39.95 10 Ne 20.18 9 F 19.00 13 Al 26.98 14 Si 28.09 15 P 30.97 5 B 10.81 6 C 12.01 7 N 14.01 8 O 16.00 2 He 4.0 Fluorine = Row 2 Fluorine Energy Level = 2

Happy / Stable Elements The number of electrons in that last ring or outer shell is called the . . . Valence Electrons 16 S 32.07 17 Cl 35.45 18 Ar 39.95 10 Ne 20.18 9 F 19.00 13 Al 26.98 14 Si 28.09 15 P 30.97 5 B 10.81 6 C 12.01 7 N 14.01 8 O 16.00 2 He 4.0 Fluorine = Column VIIA Fluorine Valence # = 7

F What are Lewis Dot Diagrams? G.N. Lewis, an American chemist, developed this shorthand system using only the element’s symbol and dots. The symbol represents the element’s nucleus. F The dots represent the #of valence electrons of that element. Fluorine Valence # = 7 or 7 electrons in outside shell

Drawing Lewis Dot Diagrams 14.01 Nitrogen 7 Cl 35.45 Chlorine 17 Using just your periodic table, draw Lewis Dot Diagrams for each of the above elements.

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

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

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

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 (- #)

Types of Bonding 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

Diatomic Molecules Covalent bonds Molecule that has 2 atoms of the same element Br2, I2, N2, Cl2, H2, O2, F2 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

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 H2O=2 atoms hydrogen, 1 atom oxygen Fe2O3=2 atoms iron, 3 atoms oxygen Ca(OH)2=1 calcium, 2 oxygen, 2 hydrogen

Independent Practice Counting Atoms

MgCl2 Writing Chemical Formulas The ratios in which compounds are formed are called their chemical formula.

Where do the subscripts come from? it comes from the oxidation number. 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. MgCl2

Remember the Oxidation Numbers? # needing / wants to get find more electrons # extra / wants to get rid of the electrons 1+ 2+ 3+ 4 3- 2- 1- Oxidation Number Varies When you combine atoms, you use the oxidation numbers to help you figure out the ratio.

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

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

Rules for Writing Ionic Formulas Drop out the “1’s” Cancel out the numbers if they are the same MgCl2

Let’s look at some examples…..

Mg+2 O-2 MgO Fe+3 O-2 Fe2O3 GROUP PRACTICE 2 = 2’s here cancel each other out – that way 1 is shown as the subscript. Fe+3 O-2 Fe2O3 2 3 These subscripts can’t cancel – so they just switch & lower.

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

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

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

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

Naming Binary Covalent Compounds Non-Metal & Non-Metal Example: CO2 1. Name the first non-metal farthest to the LEFT. Left First Carbon Right Second Oxide Write the name of the second non-metal farthest to the RIGHT and change the ending to “-ide.” Leaving a space between them Carbon Oxide

CO2 Carbon Oxide Non-Metal & Non-Metal – Continued Carbon oxide di Insert the correct prefix in front of the second (2nd) non-metal to indicate the number of atoms present. Prefixes include: 1 – mono 2 – di 3 – tri 4 – tetra 5 – penta 7 - septa Carbon oxide di Question: How do you use carbon dioxide everyday?

Independent Practice Fill in the blanks.

Covalent Compounds continued If attached to H+1 it is an ACID Will not have prefixes Examples: HCl=hydrochloric acid H2SO4=sulfuric acid H3PO4=phosphoric acid

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

Independent Practice Fill in the blanks.

Special Transition Metals Some transition metals have more than one oxidation number and a special name. Fe+2 ferrous Hg +1 mercurous Fe+3 ferric Hg +2 mercuric Cu+1 cuprous Sn+2 stannous Cu+2 cupric Sn+4 stannic

What are Polyatomic Ions? We have been working with monoatomic ions. These are single elements. Na +1, N-3, Br-1 Polyatomic Ions are covalent bonded groups of atoms and act as a unit. They usually stay together and don’t separate. (PO4) – most of the time, you see them with ( ) marks around them.

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

Writing Formulas Containing Polyatomic Ions Write down the symbol and the oxidation # for each element / polyatomic ion Criss cross and put the #s in lowest terms if necessary. (Reduce) 3. Write the formula for the compound. Mg+2 PO4-3 Li+1 SO4-2 2 3 2 1 Mg3(PO4)2 Li2SO4 Note the ( ) on multiple polyatomic ions.

Independent Practice Fill in the blanks.

Naming Compounds w/polyatomic ions Example: K2 SO4 1. Write the name of the metal first. 2. Write the name of the polyatomic nonmetal from the chart. Potassium Sulfate

Naming Compounds that start w/polyatomic ion Example: NH4Cl 1. Write the name of the polyatomic ion first. 2. Write the name of the nonmetal changing the ending to “ide.” Ammonium Chloride

Independent Practice Fill in the blanks.

Formula Mass Calculate the formula mass for the following H2SO4 KNO4 4 K2SO4 2 Ca3(PO4)2