How Atoms Combine SWBAT describe the chemical bonds that unite atoms to form compounds; describe the nature of chemical bonds that hold compounds together to the physical structures of compounds; distinguish among different types of mixtures and solutions

Definitions Compound Chemical bond Covalent bond A substance that is composed of atoms of two or more different elements that are chemically combined Chemical bond The forces that hold elements together in a compound Covalent bond The attraction of two atoms for a shared pair of electrons

Molecular Attraction Molecules What charge to molecules have? Composed of two or more atoms held together by a covalent bond What charge to molecules have? They don’t have a charge because the total number of protons and electrons are equal

Molecular Attraction Get out your lab notebooks Send one person in your group to collect a cup of water, a penny, a nickel, and a dropper Write the title and date in your lab notebook and as a group come up with a hypothesis for the following question How many drops of water can a penny hold before the water overflows the side of the penny? How many will a nickel hold?

Molecular Attraction Procedure Place the penny on a paper towel Gently squeeze drops of water onto the penny, counting how many drops hit the penny before overflowing. Record that number Repeat this procedure 2 more times and calculate the average Repeat the same procedure three times with the nickel

Molecular Attraction Glue the chart into your notebook Answer the following in your lab notebook Was there a difference in the number of drops of water the penny could hold for every trial? Why? On average, how much more could a nickel hold than a penny? Do you think a penny will hold the same amount of other liquids?

Molecular Attraction Send one person in your group to get a cup of a different liquid. Repeat the procedure on the penny with the new liquid Share the results Vinegar Saltwater Soapy water Oil

Molecules The chemical formula for molecules is written by listing the element of each atom and the number of them as a subscript. H2O 2 Hydrogen, 1 Oxygen CO2 1 Carbon, 2 Oxygen

Bonds Polar bonds Atoms in a covalent bond that do not share electrons equally Negatively charged end Positively charged end

Bonds Ion Ionic bond Metallic bond An atom that gains or loses an electron Ionic bond The attractive force between two ions of opposite charge Metallic bond The valence electrons are shared by all the atoms, like a group of positive ions floating in a sea of negative electrons. It’s very conductive.

Charges How does an atom become positively charged? When an atom has less than 4 valence electrons it can lose them. Because it loses a negative charge, it is no longer neutral, it has more protons than electrons. How does an atom become negatively charged? When an atom’s outer energy level is more than half full it can gain an electron giving it more negative particles than positive, and changing its charge

Chemical Reactions Chemical Reaction 6H2O + 6CO2 C6H12O6 + 6O2 The change of one or more substances into one or more substances 6H2O + 6CO2 C6H12O6 + 6O2 What is H2O? What is CO2? Does this equation balance? What is it showing?

Mixtures and Solutions Combination of two or more components that retain their identities Heterogeneous mixture Mixture where components are easily recognizable Solution/Homogeneous mixture The component particles cannot be distinguished

Mixtures Heterogeneous Salad Pepperoni pizza Fruit salad Homogeneous Coffee Atmosphere Pudding

Acids and Bases Acid Base A solution containing a substance that produces hydrogen ions (H+) Has a pH of less than 7 Base Produce hydroxide ions (OH-) in solution Has a pH of greater than 7

Interpreting Scientific Illustrations Magnesium Mg, Sulfur S A – 12, B – 16 Yes, Magnesium could lose its 2 valence electrons creating a positive ion (Mg2+), Sulfur could gain those 2 electrons, filling its outer energy ring and creating a negative ion (S2-) Yes they could easily combine by sharing electrons, MgS