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Chemical Bonding and Nomenclature

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1 Chemical Bonding and Nomenclature
By Paul Surko New Dimensions High School Poinciana, FL

2 8 Chemical Bond I want you to meet a friend of mine?
s Chemical Bond 8 Bonding, the way atoms are attracted to each other to form molecules, determines nearly all of the chemical properties we see. And, as we shall see, the number “8” is very important to chemical bonding. I want you to meet a friend of mine?

3 5.1 What are Molecules? Molecules are a combination of atoms bonded together. Bonding determines the chemical properties of the molecule (compound).

4 5.5 Ionic Bonding-Being Like the Noble Gases
All atoms want to have the same number of electrons as the Noble Gases. The Noble Gases have very stable electron configurations. In order to achieve the same electron configuration as the Noble Gases metal atoms will give up electrons to form positive ions (cations) and non-metal atoms will receive or take additional electrons to become negative ions (anions). IONS are charged particles. Na becomes Na+ Mg becomes Mg+2 Al becomes Al+3 Cl becomes Cl- O becomes O-2 N becomes N-3 The positive and negative ions are attracted to each other electrostatically.

5 Opposites Attract!

6 Putting Ions Together Na+ + Cl- = NaCl Ca+2 + Cl- = CaCl2
Ca+2 + O-2= CaO Na+ + O-2 = Na2O Al+3 + S-2 = Al2S3 Ca+2 + N-3 = Ca3N2 You try these! Li+ + Br- = LiBr Mg+2 + F- = MgF2 Al+3 + I- = AlI3 NH4+ + PO4-3 = (NH4)3PO4 Not NH43PO4 Sr+2 + P-3 = Sr3P2 K+ + Cl- = KCl

7 5.2 The Covalent Bond Atoms can form molecules by sharing electrons in the covalent bond. This is done only among non-metal atoms.

8 5. 3 Dot Structures-Octet Rule (All atoms want 8 electrons around them
Valence electrons are those in the outermost orbitals. They are the ones that can form bonds. Lewis came up with a way to draw valence electrons so that the bonding could be determined.

9 Rules to Write Dot Structures
Write a skeleton molecule with the lone atom in the middle (Hydrogen can never be in the middle) Find the number of electrons needed (N) (8 x number of atoms, 2 x number of H atoms) Find the number of electrons you have (valence e-'s) (H) Subtract to find the number of bonding electrons (N-H=B) Subtract again to find the number of non-bonding electrons (H-B=NB) Insert minimum number of bonding electrons in the skeleton between atoms only. Add more bonding if needed until you have B bonding electrons. Insert needed non-bonding electrons around (not between) atoms so that all atoms have 8 electrons around them. The total should be the same as NB in 5 above.

10 Let's Try it! H O H S Water H2O N
B NB E Water H2O 2 x 2 = 4 for Hydrogen 1 x 8 = 8 for Oxygen 4+8=12 needed electrons 12 N - 8 H 2 x 1 = 2 for Hydrogen 1 x 6 = 6 for Oxygen You have 8 available electrons - 4 B 4 NB = 4 bonding electrons H:O:H 8 – 4 = 4 non-bonding electrons .. H:O:H ●● .. H:O:H ●●

11 Let's Try it! H H N H S Ammonia NH3 N
B NB E Ammonia NH3 3 x 2 = 6 for Hydrogen 1 x 8 = 8 for Nitrogen 6+8=14 needed electrons 14 N - 8 H 3 x 1 = 3 for Hydrogen 1 x 5 = 5 for Nitrogen You have 8 available electrons - 6 B 2 NB = 6 bonding electrons H .. H:N:H 8 – 6 = 2 non-bonding electrons H H .. H:N:H ●● .. H:N:H ●●

12 Let's Try it! Carbon Dioxide CO2 S N H B NB E O C O
1 x 8 = 8 for Carbon 2 x 8 = 16 for Oxygen 8+16=24 needed electrons 24 N - 16 H 1 x 4 = 4 for Carbon 2 x 6 = 12 for Oxygen You have 16 available electrons - 8 B 8 NB = 8 bonding electrons 16 – 8 = 8 non-bonding electrons O::C::O O::C::O ●● ●● O::C::O ●● ●●

13 Let's Try it! O O C O Carbonate CO3-2 S N
H B NB E 3 x 8 = 24 for Oxygen 1 x 8 = 8 for Carbon 24+8=32 needed electrons 32 N - 24 H 3 x 6 = 18 for Oxygen 1 x 4= 4 for Carbon You have more available e-'s - 8 B 16 NB = 8 bonding electrons O .. O::C:O 24 – 8 = 16 non-bonding electrons .. :O: .. :O: O::C: O: ●● ●● -2 O::C: O: ●● ●●

14 5.6 Polarity-Unequal Sharing of Electrons
Even though all atoms want the same number of electrons as the Noble Gases, some want to get or give them more than others. The magnitude of this attraction for electrons is called “Electronegativity”. The more electronegative an atom is, the more it wants the electrons. Some atoms want to gain electrons so bad, they take them altogether to form negative ions. Some want to lose them so bad that they become positive ions.

15 Examples of Polar and Non-Polar Compounds
HCl The Chlorine wants the electrons more than the Hydrogen. Thus we have +δHCl-δ. NaCl Since Na is a metal it gives up its electron to form Na+ and Cl takes the electron completely to form Cl-. Cl2 (Cl—Cl) The Chlorine molecules want the electrons equally so they form a non-polar molecule with NO partial or full charges. H2O Water is a bent molecule. The lone pair of electrons from the Lewis structure distorts its shape and it becomes a very polar molecule. .. :O:H ●● O::C::O ●● ●● H CO2 Carbon Dioxide is a linear molecule. It has no lone pairs of electrons from the Lewis structure. The two oxygen atoms pull equally and make it a non-polar molecule.

16 5.7 Nomenclature Naming of Compounds
Binary Compounds have two types of atoms (not diatomic which has only two atoms). Metals (Groups I, II, and III) and Non-Metals Metal _________ + Non-Metal _________ide Sodium Chlorine Sodium Chloride NaCl Metals (Transition Metals) and Non-Metals Metal ______ +Roman Numeral (__) + Non-Metal ________ide Iron III Bromine Iron (III) Bromide FeBr3 Compare with Iron (II) Bromide FeBr2

17 5.7 Nomenclature Naming of Compounds
Binary Compounds have two types of atoms (not diatomic which has only two atoms). Metals (Transition Metals) and Non-Metals Older System Metal (Latin) _______ + ous or ic + Non-Metal ________ide Ferrous Bromine Ferrous Bromide FeBr2 Compare with Ferric Bromide FeBr3 Non-Metals and Non-Metals Use Prefixes such as mono, di, tri, tetra, penta, hexa, hepta, etc. CO2 Carbon dioxide CO Carbon monoxide PCl3 Phosphorus trichloride CCl4 Carbon tetrachloride N2O5 Dinitrogen pentoxide CS2 Carbon disulfide

18 Let’s Practice! Name the following. CaF2 Calcium Flouride K2S
Potassium Sulfide CoI2 Cobalt (II) Iodide or Cobaltous Iodide SnF2 Tin (II) Flouride or Stannous Flouride SnF4 Tin (IV) Flouride or Stannic Flouride OF2 Oxygen diflouride CuI2 Copper (II) Iodide or Cupric Iodide CuI Copper (I) Iodide or Cuprous Iodide SO2 Sulfur dioxide SrS Strontium Sulfide Lithium Bromide LiBr

19 Polyatomic Ions (partial list from page 195 (193 2nd edition))
Ammonium……………... Nitrate…………………… Permanganate…………. . Chlorate………………… Hydroxide………………. Cyanide…………………. Sulfate…………………... Carbonate………………. Chromate……………….. Acetate………………….. Phosphate………………. NH4+ NO3- MnO4- ClO3- OH- CN- SO4 2 - CO32- CrO42- C2H3O2- PO43-

20 Acids (with H in front) Binary acids (without oxygen in formula)
Hydro _________ ic Acid HCl Hydrochloric acid HBr Hydrobromic acid Oxy acids (with oxygen in formula) -ate goes to –ic and –ite goes to -ous HNO3 Nitric acid HNO2 Nitrous acid H2SO4 Sulfuric acid H2SO3 Sulfurous acid H3PO4 Phosphoric acid H3PO3 Phosphorous acid

21 Lets Practice! HF Hydroflouric acid Na2CO3 Sodium carbonate H2CO3
Carbonic acid KMnO4 Potassium permanganate HClO4 Perchloric acid H2S Hyrdogen sulfuric acid NaOH Sodium hydroxide CuSO4 Copper (II) sulfate or Cupric sulfate PbCrO4 Lead (II) chromate or Plubous chromate H2O Hydrooxic acid (no……just water) NH3 Nitrogen trihydride (no..just ammonia)



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