6-1 Notes Chemical Bonds and Compounds

Compounds have different properties from the elements that make them. O xygen and H ydrogen are both colorless, odorless gases until they combine to make WATER!!!! *** Think about the 26 letters in the alphabet that make thousands of words! Compound- substance made of two or more different elements. The atoms within the compounds are held together by chemical bonds. Bonds help determine the properties of a compound and how the atoms are arranged.

Uses chemical symbols to represent atoms of the elements and their ratios in a chemical compound. How to Write Chemical Formulas: 1.Find the symbols on the periodic table and write them side by side. 2.Determine the valence electrons for each symbol (element). 3.Determine what ratio is necessary to have a complete outer shell of 8 valence electrons. 4.Write the formula using subscripts to show the ratio.

Example: carbon dioxide 1.CO 2.C- 4 valence electrons O- 6 valence electrons 3. Since carbon has 4 and oxygen needs to 2 more to make 8, carbon will be left with 2 when one oxygen combines. One more oxygen can also bond with the two remaining electrons in carbon and make CO 2

1. calcium chloride 2. magnesium oxide 3. sodium chloride 4. aluminum oxide 5. magnesium chloride

s 8 I want you to meet a friend of mine… 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.

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

Opposites Attract!

The Ionic Bond

Ionic Compounds Held together by strong electrostatic forces Opposite charges attract High melting points and boiling points Regular structures – giant ionic lattices When melted or dissolved ionic compounds conduct electricity Ionic bond- gaining or losing electrons ***always between a metal and non-metal

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. N becomes N -3 Al becomes Al +3 Cl becomes Cl - O becomes O -2 Mg becomes Mg +2 Na becomes Na + The positive and negative ions are attracted to each other electrostatically.

Helium, neon and argon are atoms which do not react with other atoms. We call them the Inert Gases (or Noble Gases) because of this. Each of these gases has a full outer electron shell (orbit). 2p2n 10p10n18p22n He Ne Ar ,8 2,8,8

Sodium Na e.c. 2,8,1 11 protons 12 neutrons 11 electrons 11p 12n

17 protons Chlorine Cl p 18n 18 Neutrons 17 electrons e.c. 2,8,7

Na + Cl = NaCl 1 val. 7 val. Sodium gives chlorine it’s one electron and becomes +1. Chlorine gains the electron and becomes -1.

Na e.c. 2,8,1 (Na + ) Ion Atom e.c. (2,8) + The Sodium loses 1 electron to leave a complete outer shell. It is now a Sodium ion with a charge of 1 + The Sodium atom has 1 Electron in it’s outer shell. +

Cl e.c. 2,8,7 (Cl - ) Ion Atom e.c. (2,8,8) - The Chlorine gains 1 electron to gain a complete outer shell. It is now a Chlorine ion with a charge of 1 - The Chlorine atom has 7 electrons in it’s outer shell. -

Sodium atom Na Sodium ion (Na + ) Chlorine atom Cl Chlorine ion (Cl - ) The Ionic Bond The sodium atom loses one electron to attain a complete outer shell and become a positive ion (Na + ). The Chlorine atom gains one electron to attain a complete outer shell and become a negative ion (Cl – ). Strong electrostatic forces attract the sodium and chlorine ions. +-

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

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.

Examples of Polar and Non- Polar Compounds H 2 O Water is a bent molecule. The lone pair of electrons from the Lewis structure distorts its shape and it becomes a very polar molecule. NaCl Since Na is a metal it gives up its electron to form Na + and Cl takes the electron completely to form Cl -. HCl The Chlorine wants the electrons more than the Hydrogen. Thus we have +δ HCl -δ. Cl 2 (Cl—Cl) The Chlorine molecules want the electrons equally so they form a non-polar molecule with NO partial or full charges. CO 2 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... :O:H ●● H.. O::C::O ●● ●●

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 _________ideSodium Chlorine Sodium Chloride NaCl Metals (Transition Metals) and Non-Metals Metal ______ +Roman Numeral (__) + Non-Metal ________ide Iron III Bromine Iron ( III ) Bromide FeBr 3 Compare with Iron ( II ) Bromide FeBr 2

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 FeBr 2 Compare with Ferric Bromide FeBr 3 Non-Metals and Non-Metals Use Prefixes such as mono, di, tri, tetra, penta, hexa, hepta, etc. CO 2 Carbon dioxide CO Carbon monoxide PCl 3 Phosphorus trichloride CCl 4 Carbon tetrachloride N 2 O 5 Dinitrogen pentoxide CS 2 Carbon disulfide

Let’s Practice! Name the following. CaF 2 K2SK2S CoI 2 SnF 2 SnF 4 OF 2 CuI 2 CuI SO 2 SrS LiBr Strontium Sulfide Lithium Bromide Copper ( I ) Iodide or Cuprous Iodide Sulfur dioxide Copper ( II ) Iodide or Cupric Iodide Oxygen diflouride Tin ( IV ) Flouride or Stannic Flouride Tin ( II ) Flouride or Stannous Flouride Cobalt ( II ) Iodide or Cobaltous Iodide Potassium Sulfide Calcium Flouride