CHEMICAL BONDS & REACTIONS From: Science with Mr. Jones, Adapted by J.Stevens

VOCABULARY TermDefinitionExample Chemical Bonds - the attractive force that holds atoms or ions together Valence Electron an electron that is found in the outermost shell of an atom and that determines the atom's chemical properties The Octet Rule is a chemical rule of thumb that reflects observation that atoms of main-group elements tend to combine in such a way that each atom has eight electrons in its valence shell, giving it the same electronic configuration as a noble gas. Oxidation Number a number assigned to an element in chemical combination that represents the number of electrons lost (or gained, if the number is negative) by an atom of that element in the compound.

VOCABULARY TermDefinitionExample Ionic Bond – the attractive force between oppositely charged ions, which forms when electrons are transferred from one atom to another Covalent Bond –a bond formed when atoms share one or more pairs of electrons Metallic Bond - a bond formed by the attraction between positively charged metal ions and the electrons around them Molecule a group of atoms bonded together, representing the smallest fundamental unit of a chemical compound that can take part in a chemical reaction. Compound Substance made up of atoms of two or more different elements joined by chemical bonds

VOCABULARY TermDefinitionExample Chemical Structure The arrangement of the atoms in a molecule Bond Angle - the angle formed by two bonds to the same atom Bond Length - the distance between two bonded atoms at their minimum potential energy; the average distance between the nuclei of two bonded atoms Chemical Reaction - a process that involves rearrangement of the molecular or ionic structure of a substance, as opposed to a change in physical form or a nuclear reaction. Chemical Equation -a representation of a chemical reaction that uses symbols to show the relationship between the reactants and products

VOCABULARY TermDefinitionExample Reactant a substance or molecule that participates in a chemical reaction Product -- a substance that forms in a chemical reaction Coefficient Coefficients are the numbers placed before the reactants in a chemical equation so that the number of atoms in the products on the right side of the equation are equal to the number of atoms in the reactants on the left side. Subscript - A type of lettering form written lower than the things around it. In chemical formulas the number of atoms in a molecule is written as a subscript, so we write H 2 O for water which has two atoms of hydrogen for each one of oxygen. Catalyst - a substance that changes the rate of a chemical reaction without being consumed or changed significantly Inhibitor a substance that slows down or prevents a particular chemical reaction or other process, or that reduces the activity of a particular reactant, catalyst, or enzyme.

VOCABULARY TermDefinitionExample Endothermic Reaction - a chemical reaction that requires energy input Exothermic Reaction a chemical reaction in which energy is released to the surroundings as heat Enzyme a molecule, either protein or RNA that acts as a catalyst in biochemical reactions Substrate the reactant on reactions catalyzed by enzymes Decomposition Reaction - a reaction on which a single compound breaks down to form two or more simpler substances Synthesis Reaction - a reaction in which two or more substances combine to form a new compound

VOCABULARY WordDefinitionExample Combustion Reaction the oxidation reaction of an organic compound, in which heat is released Single Replacement Reaction a reaction in which one element or radical takes the place of another element or radical in a compound Double Replacement Reaction a reaction in which a gas, a solid precipitate, or a molecular compound forms from the apparent exchange of atoms or ions between two compounds Nuclear Reaction change in the identity or characteristics of an atomic nucleus that results when it is bombarded with an energetic particle, as in fission, fusion, or radioactive decay.

VOCABULARY WordDefinitionExample Fission the process by which a nucleus splits into two or more fragments and releases neutrons and energy Fusion - the process in which light nuclei combine at extremely high temperatures, forming heavier nuclei and releasing energy

SECTION 1 Key Ideas: What kinds of bonds form in chemical reactions? Vocabulary: Chemical bonds- Molecule Valence electrons- Compound Ionic bonds Covalent bond Metallic bond

INTRO Cloves vs Nutmeg

HOW DO ATOMS (H 2 O) STAY TOGETHER? Chemical Bonds A force of attraction that holds two atoms together Has a significant effect on chemical and physical properties of compounds involves the valence electrons Valence Electrons – the electrons in the outermost energy level of an atom This Lithium Atom has one valence electron

Carbon 4 valence electrons Oxygen 6 valence electrons Beryllium 2 valence electrons COUNTING VALENCE ELECTRONS

DETERMINING THE NUMBER OF VALENCE ELECTRONS BY USING THE PERIODIC TABLE *Atoms of elements in Groups 1 and 2 have the same number of valence electrons as their group number. *Atoms of elements in Group 3-12 do not have a general rule relating their valence electrons to their group number. However, they typically have between 1 or 2 valence electrons. *Atoms of elements in Groups have 10 fewer valence electrons than their group number. ( Exception - helium atoms have only 2 valence electrons, even though they are in group 18)

HOW MANY VALENCE ELECTRONS? Hydrogen Lead Xenon Sulfur Rubidium 1 Valence Electron 4 Valence Electrons 8 Valence Electrons 6 Valence Electrons 1 Valence Electron

THE OCTET RULE Atoms will combine to form compounds in order to reach eight electrons in their outer energy level. Atoms with less than 4 electrons tend to lose electrons. Atoms with more than 4 electrons tend to gain electrons. Atoms with exactly 4 electrons tend to gain electrons. There are always exceptions! What happens with an atom like Hydrogen, who only has 1 electron, and only needs 2 to fill its outer shell? CONSIDER EIGHT A HAPPY NUMBER FOR ATOMS!

THE OCTET RULE IN ACTION Notice how the sodium atom has one valence electron. It is this electron that it will try to get rid of according to the Octet Rule. Notice how this chlorine atom has seven valence electrons, one away from eight. It will try to gain one more according to the Octet Rule Where do you think Chlorine finds that one electron that it needs?

LEWIS STRUCTURE (ELECTRON DOT DIAGRAM) a way of drawing the outer energy level electrons (valence) of an atom The symbol for the element surrounded by as many dots as there are electrons in its outer energy level (valence) Examples How many valence electrons do each of these atoms have?

MAKING AN ELECTRON DOT DIAGRAM Element “X” has 8 valence electrons Write down the element’s symbol and place the first two dots on any side of the symbol. Place the rest of the dots in either a clockwise or counter clockwise manner around the symbol, with no side receiving two dots until each side gets one. If this were an atom of an element from group 1, you would just place the one dot on any side of the element.

WHAT WOULD THE ELECTRON DOT DIAGRAM LOOK LIKE? H Sr O Ne How many valence electrons does each atom have? 1 Valence Electron6 Valence Electrons 8 Valence Electrons 2 Valence Electrons

OXIDATION NUMBER The charge that an atom would have if it lost or gained electrons; ionic charge Can be helpful in determining which atoms will interact or bond with each other Example: According to electron dot diagram for Magnesium, it has two valence electrons. Because Magnesium is “unhappy” with two, it will typically lose them. If this happens it will turn into a Magnesium ion. At this point it will have an oxidation number of +2. Mg 2+

WHAT COULD THE OXIDATION NUMBER BE? H O Ne Sr +1 or -1 because it can gain or lose one electron -2 because it will gain two electrons 0 because it will not gain or lose electrons +2 because it will lose two electrons

3 TYPES OF CHEMICAL BONDS Ionic Covalent Metallic What can you describe about each of these bonds just by looking at the name?

Dogs Teaching Chemistry - Chemical Bonds.mp4

Which different groups or families of elements will most-likely interact to create these types of bonds? IONIC BONDS The force of attraction between oppositely charged ions. Occurs after a transfer or loss/gain of electrons Forms between metals and non-metals Resulting compounds have a name that usually ends in –ide Taken, not shared! - Example - Sodium Chloride (NaCl)Sodium Chloride (NaCl) Cl Na 1- 1+

COVALENT BOND A force that bonds two atoms together by a sharing of electrons Each pair of shared electrons creates a bond Forms between non-metals Example – Water (H 2 O)Water (H 2 O) OHH

TYPES OF COVALENT BONDS Different covalent bond types share a different number of electrons Single Bonds Share 2 Electrons Double Bonds Share 4 Electrons Triple Bonds Share 6 Electrons Water (H 2 O)Carbon Dioxide (CO 2 )Nitrogen (N 2 )

UNEQUAL SHARING (POLAR COVALENT BOND) The unequal sharing of electrons between two atoms that gives rise to negative and positive regions of electric charge Results from an atom’s electronegativity – the ability to attract electrons to itself Why do you think the two Hydrogen atoms share equally, but the Hydrogen and fluorine do not? Bonded hydrogen atoms showing equal sharing of electrons Hydrogen and fluorine bond with an unequal sharing of electrons Electro n Cloud

METALLIC BOND A force of attraction between a positively charged metal ion and the electrons in a metal Many metal ions pass along many electrons Many properties of metals, such as conductivity, ductility, and malleability, result from the freely moving electrons in the metal Notice how the electrons do not just stay with one ion Al3+Al3+ Al3+Al3+ Al3+Al3+ Al3+Al3+ Al3+Al3+ Al3+Al3+ Al3+Al3+ Al3+Al3+ Al3+Al3+ Al3+Al3+ Al3+Al3+ Al3+Al3+ Al3+Al3+ Al3+Al3+ Al3+Al3+ Al3+Al3+ Al3+Al3+ Al3+Al3+ Al3+Al3+ Al3+Al3+ Al3+Al3+ Al3+Al3+ Al3+Al3+ Al3+Al3+ Al3+Al3+ Al3+Al3+ Al3+Al3+ Al3+Al3+ Al3+Al3+ Al3+Al3+ Al3+Al3+ Al3+Al3+ Al3+Al3+ Al3+Al3+ Al3+Al3+ Al3+Al3+ Al3+Al3+ Al3+Al3+ Al3+Al3+ Al3+Al

RESULTS OF BONDING Molecule A neutral group of two or more non-metal atoms held together by covalent bonds Type: Diatomic - molecules consisting of two atoms of the same element bonded together Examples: H 2, F 2, O 2, N 2 Compound Composed of two or more different elements (atoms) that are chemically combined Examples: CO, NO 2, NaCl

MOLECULE, COMPOUND, OR BOTH? H 2 Hydroge n NO 2 Nitrogen Dioxide Cl 2 Chlorin e O 2 Oxyge n NO Nitric Oxide CO 2 Carbon Dioxide N 2 Nitroge n H 2 O Wate r CH 4 Methan e Atoms Bonding Song

INTER-MOLECULAR BONDS There is another type of bond that happens between molecules – hydrogen bonding This occurs in water molecules and gives water special properties Cohesion – water molecules stick to each other Adhesion – water molecules stick to other substances

WATER Has covalent and hydrogen bonds Why do you think hydrogen bonds form? Atoms Bonding Song

BONDING BASICS ACTIVITY Divide into groups of 4

SECTION 2 Key Ideas: When do chemical reactions take place? What is the role of energy in chemical reactions? What is a chemical equation? How do I understand what a chemical equation is telling me? What is photosynthesis? What are the reactants and products? What is cellular respiration? What are the reactants and products? Vocabulary: Chemical Reactions- Endothermic Rxn Chemical Equation- Exothermic Rxn Reactant Product Coefficient Subscript

CHEMICAL REACTIONS Chemical Change occurs Atoms are rearranged, and chemical bonds are broken and reformed One or more substances change to produce one or more different substances Energy must be added to break bonds Many forms of energy can be used: Heat Electricity Light Sound Energy is always conserved in a chemical reaction (law of conservation of energy)

PHYSICAL CHANGE a change in shape, size, color, or state a change without a change in chemical composition a change that is reversible Examples tearing paper cutting your hair change in state Remember!!! Physical changes are not indicative of a chemical reaction

CHEMICAL CHANGE a change in which a substance becomes another substance having different properties a change that is not reversible using ordinary physical means Changes that usually cause, heat, sound, light, odor, fizzing/foaming, color changes You usually need more than one of the above characteristics to be considered a chemical change! Examples mixing vinegar & baking soda burning a piece of wood soured milk A chemical analysis is the only 100% way to know a chemical change has occurred.

CHEMICAL EQUATION Shorthand form for writing what compounds are used to begin the reaction and what compounds are formed after the reaction occurs Examples: 2H 2 + O 2 → 2H 2 O CH 4 + 2O 2 → CO 2 + 2H 2 O C 6 H 12 O 6 + 6O 2 → 6CO 2 + 6H 2 O + energy

COMPONENTS OF A CHEMICAL EQUATION 2H 2 + O 2 2H 2 O → (Reactants) (Products) (Yield) Chemical Formulas Chemical Formula Subscripts Coefficient What does a Coefficient meant? What does a subscript mean? What does “Yield” mean? Reactants are always on what side of the yield sign? Products are always on what side of the yield sign? Coefficient Subscript

Any time you have something written above the “Yield” arrow, it is a catalyst. A catalyst is something that speeds up a chemical reaction SYMBOLS OF A CHEMICAL EQUATION

PRACTICE – WRITE IN YOUR NOTES In CO 2 (carbon dioxide) how many Carbon atoms are there? How many Oxygen atoms? In 2NH 3, (windex) how many Nitrogen atoms are there? How many Hydrogen atoms? In H 2 SO 4 (battery acid) how many of each type of atom is there? In 3CHNaO 3 (Alka Seltzer), how many of each type of atom is there? In C 9 H 8 O 4 (aspirin), how many of each type of atom is there? What kind of bonds do you think these all form? Why?

WHAT IS PHOTOSYNTHESIS? Photosynthesis is: basically how plants make their own food! How does it work? -> Basics of Photosynthesis Basics of Photosynthesis Photosynthesis from space Photosynthesis from space

PHOTOSYNTHESIS Formula: What are the reactants in photosynthesis? What are the products?

WHAT IS CELLULAR RESPIRATION? Cellular respiration is: how cells in organisms use oxygen and sugar to make energy needed for us to survive How does it work? -> Cellular Respiration Overview

Formula: What are the reactants in cellular respiration? What are the products in cellular respiration? CELLULAR RESPIRATION

HOW ARE PHOTOSYNTHESIS AND CELLULAR RESPIRATION RELATED? What do you notice?

ENERGY AND CHEMICAL REACTIONS Exothermic Reaction A chemical reaction in which energy is released. The products have greater bond energy than the reactants C 6 H 12 O 6 + 6O 2 → 6CO 2 + 6H 2 O + energy (respiration) Exothermic example Endothermic Reaction A chemical reaction in which energy is absorbed. The products have lower bond energies than the reactants 6CO 2 + 6H 2 O + energy → C 6 H 12 O 6 + 6O 2 (photosynthesis) Can you think of other reactions where energy is gained or released?

RATES OF CHEMICAL REACTIONS (RX) Temperature – a measure of the average kinetic energy of the particles in a sample of matter Ex. Increasing the temperature when cooking increases reaction rate Surface area – amount of material that comes into contact with the reactants Ex. Cutting a potato into smaller pieces when cooking (larger surface area (smaller pieces) increases reaction rate) Concentration – amount of substance per volume Ex. Turning the valve on a gas stove to increase the concentration of methane molecules (this will increase the rate of rx) Ex. Too much salt in a glass of water will decrease the rate of rx Catalysts (enzymes) –substances that help speed up chemical reactions, but are not consumed in the reaction Inhibitors – substance that delays, slows or prevents a chemical rx; can make rx more controllable The rates at which chemical reactions can take place are influenced by the following:

LAW OF CONSERVATION OF MASS Proposed by Antoine Lavoisier StoichimetryStoichimetry In a chemical reaction, atoms are neither created nor destroyed All atoms present in the reactants are also present in the products Chemical equations must account for/show the conservation of mass → balancing equations H 2 + O 2 H2OH2O → In its present form, does this chemical equation show a conservation of mass? How would you balance this equation to show the conservation of mass? 22 Reactants H → 2 O → 2 Products 4242 H → 2 O →

SECTION 3 Key Ideas: What are different types of chemical reactions? How is a nuclear reaction different than a chemical reaction? Vocabulary: Synthesis Reaction- Nuclear Reaction Decomposition Reaction- Fission/Fusion Combustion Single Replacement Rxn Double Replacement Rxn

TYPES OF CHEMICAL REACTIONS 4Types Synthesis (creating) Decomposition (separating) Combustion (burning) Displacement/Replacement (switching) O2O2 H2H2 What does H 2 & O 2 gas create? Out of the four types of reactions, which would describe the chemical reaction taking place to the right?

SYNTHESIS (CREATING) Two substances combine to make a new substance Ex: Synthesis of Carbon Dioxide 2CO(g) + O 2 (g) → 2CO 2 (g)

DECOMPOSITION (SEPARATING) A complex substance gets broken down to form two separate substances Ex: Electrolysis of water to make hydrogen and oxygen 2 H 2 O ---> 2 H 2 + O 2

COMBUSTION (BURNING) Always involves O 2 (Oxygen) Oxygen reacts with another element or compound to form water (H 2 O), carbon dioxide (CO 2 ) and heat Exothermic Reactions

DISPLACEMENT/REPLACEMENT (SWITCHING) Two types: Single replacement and double replacement Single replacement (substitution): One element trades places with another element in a compound Ex: Zn + 2 HCl → ZnCl 2 + H 2 Ex:

REPLACEMENT/SWITCHING Double Replacement: involves two replacements to form two entirely new compounds Ex: AgNO 3 + HCl → AgCl + HNO 3 Ex: Fe 2 O 3 + HCl → FeCl 3 + H 2 O

PRACTICE TYPES OF RXNS Worksheet

HINTS FOR BALANCING EQUATIONS Count the atoms List the number of atoms of each element to see which elements must be balanced Use a coefficient to add atoms to one side of the equation Start with the reactant or product that has the greatest number of different elements Add a coefficient to another reactant or product Make sure that the coefficients in your balanced equation are the smallest whole numbers possible (they should have no common factor other than one) Tutorial on Balancing Equations

CHEMICAL VS. NUCLEAR RX Chemical Reaction Atoms are rearranged, and chemical bonds are broken and reformed New substance is formed C 6 H 12 O 6 + 6O 2 → 6CO 2 + 6H 2 O + energy (respiration) Nuclear Reaction Fission and Fusion Involves at least two nuclei, where one has to have all its electrons removed, by bringing it to very high temperatures. Why must the electrons be removed? A neutron is then “slammed” into another nucleus, causing the nucleus to break apart (fission) or combine to create a new nucleus (fusion) Fusion Fission Reaction.mp4 How a Nuclear Reactor Works - IMechE.mp4

HOW DO WE USE NUCLEAR RXNS? Read nuclear power article Write Journal Entry Watch New Nuclear PowerNew Nuclear Power