1 Name: ___________________________ Date: ______________ Unit 2: Ecological Biochemistry Unit 2A- Basic Chemistry NOTES Atoms are the Basic Units of Matter Atoms are incredibly small. Placed side by side, 100 million atoms would make a row only about 1 centimeter long—about the width of your little finger! What are Atoms made of? Atoms are made of particles called protons, neutrons, and electrons. Protons have a __________________ (+) charge Electrons have a _________________ (-) charge Neutrons are ___________________ (no charge) *Atoms normally have equal numbers of electrons and protons, making them neutral Elements Elements are pure substances made of only ______________________ of atom Elements are listed in the periodic table of elements They are arranged in order of their atomic numbers An atom is the smallest unit of an element that has the properties of that element Summary/ Additional Notes: 2 Atomic Number and Mass Number The atomic number of an element is the number of _____________________ (typically the same as the number of electrons) The mass number/atomic mass of an element is the number of _______________ plus the number of _______________ Use your periodic table to complete the following chart: Element Symbol Atomic Number Mass Number Helium He 2 4 Magnesium Mg 12 Zinc Zn 30 Bromine Br Aluminum Al Summary/ Additional Notes: Number of Protons Numbers of Neutrons Number of Electrons 2 12 65 35 80 45 13 14 35 3 Important Elements for Biology The five most abundant elements in living things are: 1. Hydrogen – 10% 2. Oxygen – 65% 3. Nitrogen – 4% 4. Carbon – 19% 5. Phosphorus – 1% Label the pie graph with each of the element most common in living things Molecules, Compounds, and Chemical Formulas A molecule is made when 2 or more of _____________________ are joined together (Ex: O2, H2O) A compound is a substance formed by the combination of two or more ___________________ elements (Ex: H2O, C6H12O6) All compounds are molecules, but not all molecules are compounds Chemical Formula- written shorthand showing the composition of a compound Chemical Formulas Coefficient: tells how many _______________________ of that substance (the large number BEFORE the formula) Subscript: goes with the element symbol preceding the number; tells how many _________________ of that element within one molecule of the substance (small number WITHIN the formula). Summary/ Additional Notes: 4 Fill in the table Example 2: 6CO2 What is the coefficient? _______ What is carbon’s subscript? ________ What is oxygen’s subscript? ________ How many molecules of this compound are represented by this formula?________ How many atoms TOTAL are present in this molecule? ______ Chemical Bonds The atoms in compounds are held together by chemical bonds. Making bonds involves the electrons that surround each nucleus. The electrons that are available to form bonds are called valence electrons. Summary/ Additional Notes: This type of drawing is called a Bohr model 5 Valence Electrons The electrons of an atom are spread out in different layers around the nucleus to make an “_________________________” These layers are called energy levels 2 electrons go in the first energy level 8 electrons can go in the second energy level and beyond (octet rule) If there are not 8 electrons for the outer level, these empty spots are called vacancies and some electrons are thus unpaired The unpaired electrons in the outer layer are the valence electrons The valence electrons can pair with those from other atoms to “fill” the vacancy This creates a molecule Water Molecule Bohr Model vs. Lewis Dot Structure Bohr Model: shows all of the electrons in their energy levels Summary/ Additional Notes: Lewis Dot Structure: shows just the valence electrons in the outer energy level 6 Draw a Bohr model and a Lewis Dot structure for each of the elements listed below. Hint: you need to know the number of what to draw these? Element Bohr Lewis Dot Carbon Nitrogen Reactive vs. Stable The reactivity of an atom is determined by the number of vacancies in its outer energy level If there are vacancies, the atom is reactive/unstable If there are no vacancies, the atom is nonreactive/stable If the vacancies are filled due to bonding, the molecule is stable The main types of chemical bonds are 1. ionic bonds 2. covalent bonds There are other types of bonds and interactions but they are not as strong as these two types Summary/ Additional Notes: 7 1. Ionic Bonds An ionic bond is formed when one or more electrons are transferred from one atom to another. An atom that loses electrons becomes positively charged. An atom that gains electrons has a negative charge. These positively and negatively charged atoms are known as ions. These oppositely charged ions have a strong attraction for each other, forming an ionic bond. 2. Covalent Bonds When electrons are shared by atoms instead of transferred. The moving electrons travel about the nuclei of both atoms, forming a covalent bond. A covalent bond can be a… Single Covalent Bond: atoms share 2 electrons (1 pair) Double Covalent Bond: atoms share 4 electrons (2 pairs) Triple Covalent Bond: atoms share 6 electrons (3 pairs) Summary/ Additional Notes: 8 HONC Bonds between the most important biological atoms will be covalent The number of bonds each can make is important for the compounds that will be created using these atoms H O N C 1 2 3 4 _________________________ _________________________ _________________________ Hydrogen -can form 1 single bond Oxygen- can form 2 single bonds or one double bond Nitrogen- can form 3 single bonds or 1 double bond and 1 single bond Carbon- can form 4 single bonds or 2 double bonds, or 1 double bond and 2 single bonds (no quadruple bond!) Structural formulas Show you… _____________ - the types of elements in the molecule - the number of atoms of each element AND - the arrangement of atoms and location of covalent bonds. Shows the two dimensional shape of the molecule. _____________ Summary/ Additional Notes: 9 Chemical Reactions Chemical Reactions: process that ____________________ or transforms one set of chemicals into another set of chemicals. Involves changes to the chemical bonds that join atoms in compounds. Reactants: elements or compounds that _________ into a chemical reaction Products: elements or compounds ______________ by a chemical reaction HINT: Reactants react to produce products! *Bonds of the reactants are broken and new bonds form in the products Chemical Equations Chemical Equation: a mathematical representation of a chemical reaction. It shows the numbers and types of compounds involved. What process is this equation for? ___________________________________ 6O2 + Summary/ Additional Notes: C6H12O6 6CO2 + 6H2O + _____ 10 Balancing Chemical Equations The Law of Conservation of Matter: matter (atoms and elements) in a chemical reaction ____________________ be created or destroyed. Only the arrangement of the atoms is changed, NOT the number or types. Therefore both sides of a chemical equation must be “______________________” (have the same number of atoms). Are these equations balanced? C + 2H2 --> CH4 Na2SO4 + CaCl2 --> CaSO4 + NaCl C2H6 + O2 --> CO2 + H2O 2Al2O3 --> 4Al + 3O2 Summary/ Additional Notes: