Chemical Bonds & Reactions

Chemical Bonds & Reactions

CHEMICAL BONDS & REACTIONS - + + - From: Science with Mr. Jones, Adapted by J.Stevens VOCABULARY Term Definition Chemical Bonds The attractive force that holds atoms or ions together Valence Electron Electron in the outermost shell

of an atom that determines the atoms chemical properties Ionic bond The attractive force between oppositely charged ions, which form 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 Example VOCABULARY

Term Definition Molecule Group of atoms that are held together by chemical forces Compound Substance made up of atoms of two or more different elements joined by chemical bonds Chemical Reaction Reaction (Rxn) where chemical bonds are broken in reactants and new ones are created in products Chemical Equation Representation of a chemical

reaction that uses symbols to show the relationship between reactants and products Reactant Substance or molecule that participates in a chemical reaction (left side of chemical equation) Example VOCABULARY Term Definition Product Substance that forms in a chemical reaction (on right hand side of chemical equation) Coefficient Number in front of a compound that

tells you how many molecules of that compound you have Subscript Small number in a chemical equation that comes after a certain element and tells you how many atoms of that element you have Catalyst Substance that increases the rate of a chemical reaction without being used up Inhibitor Substance that slows down or stops the rate of a chemical reaction Example VOCABULARY Term Definition

Endothermic Reaction Rxn that requires or absorbs energy Exothermic Reaction Rxn in which energy is released to the surrounding environment as heat Decomposition Reaction (Rxn) Rxn in which a single compound breaks down to form two or more simpler substances Synthesis Rxn Rxn in which 2 or more substances combine to form a new substance

Combustion Oxidation rxn of an organic compound where heat is released Single Replacement Rxn Rxn in which one element takes the place of another element in a compound Example VOCABULARY Term Definition Double Rxn in which a gas, solid, or Replacement Rxn compound forms from the exchange of atoms or ions between two compounds Nuclear Reaction

Continuous chain of nuclear fission/fusion reactions Photosynthesis basically how plants make their own food Cellular Respiration how cells in organisms use oxygen and sugar to make energy needed to survive Example SECTION 1 Key Ideas: What kinds of bonds form in chemical reactions? Vocabulary:

Chemical bonds Valence electrons Ionic bonds Covalent bond Metallic bond - Molecule - Compound INTRO Cloves vs Nutmeg HOW DO ATOMS (H2O) 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 that determine an atoms chemical properties -

This Lithium Atom has one valence electron + - + + - COUNTING VALENCE ELECTRONS - - - + - + ++ + + + + +

+ + + - + - - + - + - + + - + -

- - - - - Carbon Oxygen Beryllium 4 valence electrons 6 valence electrons 2 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 13-18 have 10 fewer valence electrons than their group number. (Exception - helium atoms have only 2 valence electrons, even though they are in 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 6 - 7

- - - 5 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. - - - +++ + ++ + + + ++ ++ + + ++

- 4 - - 1 - 3 - - - - - - 1

- - + + + ++ ++ + ++ + 2 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. - - - -

- 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 . . Al : .N : Mg: Aluminum Nitrogen

Magnesium . How many valence electrons do each of these atoms have? WHAT WOULD THE ELECTRON DOT DIAGRAM LOOK LIKE? 1 Valence Electron 6 Valence Electrons H O How many valence electrons does each atom have? Ne 8 Valence Electrons Sr 2 Valence 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 Chemis try - Chemical Bonds. mp4 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, 1- not shared! Na1+ Cl - -

- - - - - - - ++ + + + + + + - - - -

++ + + + - - - - - - - Example - Sodium Chloride (NaCl) - Which different groups or families

of elements + will most-likely + interact to + create these types of- bonds? 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 H O H - + ++ + + + + + +

- - - + - - Example Water (H2O) TYPES OF COVALENT BONDS Different covalent bond types share a different number of electrons Water (H2O) - Carbon Dioxide (CO2) Nitrogen (N2) - -

- - + ++ + + + + + + + ++ + + + + + - - - -

- - - ++ + + + + - - - - - - - - - - - -

++ + + + + + + - - + + + + + - - - ++ - - - - ++

+ + + + + - - + Single Bonds Share 2 Electrons Double Bonds Share 4 Electrons Triple Bonds Share 6 Electrons 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 - Al3+ Al3+ - Al Al3+ 3+ - Al3+ Al3+ - - - Al 3+

Al3+ -Al - 3+ 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 Al3+ Al3+ Al3+ - Al 3+ 3+ - -

Notice how the electron s do not just stay with one ion 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: H2, F2, O2, N2 Compound Composed of two or more different elements (atoms) that are chemically combined

Examples: CO, NO2, NaCl MOLECULE, COMPOUND, OR BOTH? NO 2 og Nitr i en D N2 og e Nitr e oxid Cl 2 n Chlo rine

CO 2 O2 ioxide Carbon D CH Oxy gen 4 M et NO e Oxid c i r t Ni Atoms Bonding Song han

e H2 Hydroge n H 2O er Wat 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: 2H2 + O2 2H2O CH4 + 2O2 CO2 + 2H2O C6H12O6 + 6O2 6CO2 + 6H2O + energy

COMPONENTS OF A CHEMICAL EQUATION Chemical Formulas Chemical Formula 2H2 + O2 2H2O Subscript Coefficient Coefficient Subscripts (Yield) (Products) (Reactant s) What does a Coefficient mean? What does a subscript mean? What does Yield mean?

Reactants are always on what side of the yield sign? SYMBOLS OF A CHEMICAL EQUATION PRACTICE WRITE IN YOUR NOTES In CO2 (carbon dioxide) how many Carbon atoms are there? How many Oxygen atoms? In 2NH3, (windex) how many Nitrogen atoms are there? How many Hydrogen atoms? In H2SO4 (battery acid) how many of each type of atom is there? In 3CHNaO3 (Alka Seltzer), how many of each type of atom is there? In C9H8O4 (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 Photosynt hesis

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 O verview CELLULAR RESPIRATION Formula:

What are the reactants in cellular respiration? What are the products in 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 C6H12O6 + 6O2 6CO2 + 6H2O + energy (respiration) Endothermic Reaction

A chemical reaction in which energy is absorbed. The products have lower bond energies than the reactants 6CO2 + 6H2O + energy C6H12O6 + 6O2 (photosynthesis) Can you think of other reactions where energy is gained or released? RATES OF CHEMICAL REACTIONS (RX) The rates at which chemical reactions can take place are influenced by the following: 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 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) What does H2 & O2 gas create? Out of the four types of reactions,

which would describe the chemical reaction taking place to the right? H2 O2 SYNTHESIS (CREATING) Two substances combine to make a new substance Ex: Synthesis of Carbon Dioxide 2CO(g) + O2(g) 2CO2(g) DECOMPOSITION (SEPARATING) A complex substance gets broken down to form two separate substances Ex: Electrolysis of water to make hydrogen and oxygen 2 H2O ---> 2 H2 + O2 COMBUSTION (BURNING) Always involves O2 (Oxygen) Oxygen reacts with another element or compound to form water (H2O), carbon dioxide

(CO2) 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 ZnCl2 + H2 Ex: REPLACEMENT/SWITCHING Double Replacement: involves two replacements to form two entirely new compounds Ex: AgNO3 + HCl AgCl + HNO3 Ex: Fe2O3 + HCl FeCl3 + H2O PRACTICE TYPES OF RXNS Worksheet CHEMICAL VS. NUCLEAR RXN Chemical Reaction

Atoms are rearranged, and chemical bonds are broken and reformed New substance is formed C6H12O6 + 6O2 6CO2 + 6H2O + 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 Power

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