Chapter 6 Chemical Bonds and Compounds

How do these skydivers stay together How do these skydivers stay together? How is this similar to the way atoms stay together?

Describe how compounds are made from combinations of atoms. Objectives: Describe how compounds are made from combinations of atoms. Explain how chemical formulas represent chemical compounds.

Section 6.1 If we look at all the different things around us it is easy to see that everything is not an element. But we also know that there are just over 100 different elements and they make up millions of different substances. How many letters in the alphabet? How many words are made from those 26 letters? Atoms are held together in compounds by chemical bonds.

+ Bonds determine the properties of a compound. Many times the properties of compounds are often different from the properties that make them. EXAMPLE + = CALCIUM CHLORIDE CALCIUM CHLORINE

CALCIUM ~ A GROUP 2 ALKALINE EARTH METAL (soft, silvery metallic solid) CHLORINE ~ A HALOGEN is a greenish gas very poisonous to humans These two come together to form a product we use to melt ice that forms on streets and sidewalks.

In every family the number of males to females varies In every family the number of males to females varies. In this family there are 3 females to 2 males. Me, mom and my sister THE GIRLS. Dad and my brother THE BOYS. So there is a 3:2 ratio of females to males.

Atoms always combine in predictable numbers For example NH3 is ammonia. The compound ammonia always has three hydrogen atoms for every nitrogen atom.

Chemical formulas Chemical formulas use chemical symbols to represent the atoms of the elements and their ratios. EX) H2O CO2 HCl NH3 CH4 C3H8

Two totally different substances……… This chart shows the names, atoms, ratios and chemical formulas for several chemical compounds. Notice methane and propane are made from atoms of the same elements but in different ratios. Two totally different substances……… Propane in the tank on your grill and methane given off when cows BURP!!!!!!!!!!!!!!!!!!!

How to Write A Chemical Formula Find the symbols found in the compound, write them down side by side. Place subscripts to the right side of corresponding symbols (you can find subscripts by using the oxidation numbers) Remember the subscript “1” is never used CH4 H2O2 2C4H4o6-2 Subscript: a number written to the right of a chemical symbol and slightly below it. It indicates how many of each element in found in the compound.

Same elements, different compounds Which one would you want to drink? or

Review How many different atoms are in C12H22O11? Ans: 12 carbon atoms + 22 hydrogen atoms 11 oxygen atoms = 45 total atoms

How do properties of compounds compare with the elements that make them? Ans: most of the time VERY different If a chemical formula has no subscripts For example CO (carbon monoxide) What is the ratio of the atoms? Ans: 1 to 1

If CO2 is carbon dioxide then is H2O Dihydrogen monoxide If CO2 is carbon dioxide then is H2O Dihydrogen monoxide? No silly teacher H2O is water!!!!!!!!!

Section 2 objectives Explain how electrons are involved in chemical bonding. Describe what the different types of chemical bonds are. Determine how chemical bonds affect structure.

What are some different ways workers at the construction sites that we saw in downtown Atlanta connect materials? Glue Nails screws

Chemical bonds between atoms involve electrons Chemical bonds are the “glue” that holds atoms of elements together Chemical bonds have an effect on the chemical and physical properties of compounds

Transfer Please!!!!!!!! When a college student needs money to cover rent and other needs they call mom and dad and ask them to transfer money to their checking account. Mom or dad calls the bank and says they want to transfer money to their account.

A similar thing happens when the atom of a metal transfers an electron to the atom of a nonmetal.

Ionic bond: a chemical bond that involves the electrical attraction between a negative ion and a positive ion Example: an atom from Group 1, like sodium (Na) forms a positive ion Na+ & meets an atom from Group 17 (a Halogen) chlorine (Cl) forms a negative ion Cl- the bond forms is ionic. NaCl is table salt. Just like opposite ends of a magnet attract~~~~ these oppositely charged ions attract each other.

So how we name these monsters? Name the positive metal element~ example sodium (Na) Next take the name of the negative, nonmetal element, chlorine (Cl) and give it the ending –ide chloride Now combine the two names making that monster’s name sodium chloride. We just call it salt!!!!

Let’s try some more! What would lithium and iodine be called? What about sodium and fluorine? And calcium and chlorine? Wow that is amazing YOU just learned to name ionic compounds!!!!!!!!!!!

Salts are formed from the positive ion of a metal and negative ion of a nonmetal. Not all salts are the kind we put on our French fries. That is NaCl. Calcium chloride CaCl2 is put on roads and sidewalks to melt snow and ice. The metal ion in salts give off a characteristic flame color as you saw in the lady liberty fireworks site. http://www.driveaway.com/lady_liberty/liberty_dl.htm

Properties of Ionic Bonds Solid at room temp High melting and boiling point temps Dissolves easily in water Good Conductors, but only in water Brittle, Crystal-like structure

When 2 girls share the responsibilities of being head cheerleader what do we call them? They are co-head cheerleaders. A chemical bond in which a pair of electrons are shared between two atoms is covalent bonding. The electrons spend as much time around one atom as they do the other atom. They zip back and forth between atoms. Some common substances held together by covalent bonds are: carbon dioxide (CO2), methane (CH4) and several elements exist covalently bonded to themselves. H2, N2, O2, F2, Cl2, Br2, & I2.

Properties of Covalent Bonds A group of atoms held together by covalent bonds is called a molecule. Properties of Covalent Bonds Lower Melting Point & Boiling Point Temps Will NOT dissolve in water Does NOT conduct electricity

Polar covalent bonds A covalent bond in which the bonds are shared unequally. Water is a perfect example of a polar covalent bond. That is why water is a good solvent and we take a bath in it!! It has both positive and negative parts.

So What does Polar Mean? Anything that has two extremes (like a magnet) Polar Covalent Bonds occur when the molecule is asymmetrical. This causes one end of the molecule to be more positive & and the other more negative

Review section 2 What part of an atom is involved in bonding? Ans: the electron cloud (ie valence electrons) Compare ionic and covalent bonds. Ionic: gaining/losing electrons Covalent: sharing electrons A polar covalent bond forms when? ans: two atoms share electrons unequally

Section 3 Substances’ properties depend on their bonds Metals have unique bonds. They slide easily past each other giving metals their useful qualities (ie malleable, ductile, shiny and good conductors) Properties of metals are determined by metallic bonds. Metallic Bond- a covalent bond with equal sharing of electrons with metal elements (Non-Polar)

Properties of Metals Good Conductors of electric current & heat Have high Melting points Except Mercury, all metals are solid at room temperature. Easily shaped & drawn into a wire

Metallic Bonds In metallic compounds, atoms can slide past one another. It is as if the atoms are swimming in a pool of surrounding electrons. Pounding the metal simply moves these atoms into other positions. This makes metals ideal for making coins!

Remember Ionic Compounds: Made when a positive ion (Metal) bonds with a negative ion (Nonmetal) Dissolve easily in water Good conductors of electricity (Nerve signals)

Remember Covalent Bonds Occur between 2 nonmetals Atoms covalently bonded form Molecules Melts easily Does not dissolve in water Poor conductors

Bonds can make elements look different. Carbon atoms all make up these substances, So how are they all different? copper diamond fragment graphite fragment

Carbon Can Exist as a Diamond, Graphite, and Fullerene Diamonds are the hardest natural substance. Made up of Carbon atoms that are covalently bonded to 4 other carbon atoms.

Diamonds The Cullinan I, a pear shaped diamond weighing 530.20 carats is also known as the Star of Africa. Cullinan I was placed by King Edward in the Sovereign's Royal Sceptre as part of the Crown Jewels, and it is now on display in the tower of London. Estimated value of Cullinan I is over $400 million!

Graphite Dark, Slippery component of pencil “lead” Each Carbon atoms bond to three other atoms to form a 2 dimensional layer.

Fullerene Third form of Carbon Buckminsterfullerene has molecules shaped like a soccer ball. Man-made carbon molecule. Ranges from 20-100 atoms per molecule

review Three forms of carbon are? Ans: diamond, graphite and fullerene Metallic bonds make many metals? ans: good conductors of electricity