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Name the levels of life from the smallest to the largest!!! WHAT HAVE WE LEARNED? List levels of life. Name 3 subatomic particles, charges, how to calculate and location What is in the element box? Important elements in organisms Levels of the Organization of Life • • • • • • • • Subatomic particle Atom Molecule(compound) Organelle Cell Tissue Organ Organ system organism populations community ecosystem(biome) biosphere What is this a picture of ? Name 3 facts about this object! ELEMENTS, ATOMS, AND MOLECULES Copyright © 2009 Pearson Education, Inc. How are atoms studied? • Atoms are the building blocks of matter • Atoms are too small in size to study easily • Size of Earth : soda can = soda can : atom Democritus • Not until around 460 B.C., did a Greek philosopher, Democritus, develop the idea of atoms. He asked this question: If you break a piece of matter in half, and then break it in half again, how many breaks will you have to make before you can break it no further? Democritus thought that it ended at some point, a smallest possible bit of matter. He called these basic matter particles, atoms. Democritus • He said in the world this was “atoms and void”. No space between the atoms. ATOMS Atoms: smallest unit of matter that still retains the properties of an element. . 2.4 Atoms consist of protons, neutrons, and electrons • An atom is the smallest unit of matter that still retains the properties of a element – Atoms are made of over a hundred subatomic particles, but only three are important for biological compounds – Proton—has a single positive electrical charge (nucleus) – Electron—has a single negative electrical charge (shells) – Neutron—is electrically neutral (nucleus) Copyright © 2009 Pearson Education, Inc. Electron cloud Nucleus 2 Protons 2 Neutrons 2 Electrons 2e– Mass number = 4 Protons Protons are located in the nucleus of the atom. They are positively charged. Neutrons Neutrons are located in the nucleus. They have NO charge! Electrons Electrons are located in the shells around the atom. They are negatively charged. Electron shells a) Atomic number = number of Electrons b) Electrons vary in the amount of energy they possess, and they occur at certain energy levels or electron shells. c) Electron shells determine how an atom behaves when it encounters other atoms Parts of an Atom Protons and neutrons make up the nucleus and has the most mass. Electrons do not weigh as much. SO the atomic mass is only the Protons + the Neutrons How Do You Think These Pictures are Related? What do you think is in this picture? Atoms make up substances called elements which are the building blocks of matter. There are 110 elements 2.1 Living organisms are composed of about 25 chemical elements • Living organisms are composed of matter, which is anything that occupies space and has mass (weight) – Matter is composed of chemical elements – Element—a substance that cannot be broken down to other substances – There are 92 elements in nature—only a few exist in a pure state – Life requires 25 essential elements; some are called trace elements Copyright © 2009 Pearson Education, Inc. 1. ELEMENTS ARE PURE SUBSTANCES MADE OF ONLY 1 KIND OF ATOM AND ARE THE BUILDING BLOCKS OF MATTER. 2. ELEMENTS CANNOT BE BROKEN DOWN INTO A SIMPLER SUBSTANCE 3. ELEMENTS HAVE THEIR OWN UNIQUE SET OF PROPERTIES THAT NO OTHER ELEMENT HAS. • ELEMENTS ARE MADE OF ONLY 1 KIND OF ATOM • SOME COMMON ELEMENTS – HYDROGEN (H), HELIUM (He), OXYGEN (0), – Notice that the first letter is capital and the next letter is lower case. Why Are Elements Different? • Elements differ in their number of protons, neutrons, and electrons. This is why their atomic numbers and masses are different. • Helium has two protons, two neutrons, and two electrons • Carbon has six protons, six neutrons, and six electrons Copyright © 2009 Pearson Education, Inc. Why Do Some Elements Have Different Symbols? They are older elements that were name in a different language like Latin. Copper – cuprum Iron – Ferrous Gold - aurum Silver - argentum Elements in Organisms • 4 elements that make up 96% of human body: Carbon(C), Hydrogen(H), Oxygen(O), Nitrogen(N) 2.2 CONNECTION: Trace elements are common additives to food and water • Some trace elements are required to prevent disease – Without iron, your body cannot transport oxygen – An iodine deficiency prevents production of thyroid hormones, resulting in goiter Copyright © 2009 Pearson Education, Inc. 2.2 CONNECTION: Trace elements are common additives to food and water • Several chemicals are added to food for a variety of reasons – Help preserve it – Make it more nutritious – Make it look better • Check out the “Nutrition Facts” label on foods and drinks you purchase Copyright © 2009 Pearson Education, Inc. Where Do you Find a Information on All Elements? Element Info in Each Box Atomic weight Atomic Number Symbol Name Information from the periodic table Atomic Number- Number of Protons in an atom Silver = 47 protons Atomic Weight - total number of particles in an atom's nucleus Atomic Weight is not very helpful – you need to find the atomic mass To find the Atomic Mass: Round the atomic weight Krypton's mass number is 84 since its atomic weight, 83.80, rounds up to 84. Mass Number = (Number of Protons) + (Number of Neutrons) 84 = 36 + 48 2.4 Atoms consist of protons, neutrons, and electrons • Neutrons and protons are packed in the atom’s nucleus – The negative charge of electrons and the positive charge of protons keep electrons near the nucleus – The number of protons is the atom’s atomic number – Carbon with 6 protons has an atomic number of 6 – The mass number is the sum of the protons and neutrons in the nucleus (carbon-12 is written 12C) Copyright © 2009 Pearson Education, Inc. VALENCE ELECTRONS • Number of electrons in the outermost. Determines how the element will bond. GROUPS: determined by valence electrons. Group 1 – one valence electron Group 2 – 2 valence electrons Now let’s learn how to draw an element • Two models we will use: 1.Bohr’s model 2.Lewis Dot Structure How do you calculate Valance Electrons? You determine the number of electrons. Then place the electrons in electron shells. Bohr’s Model: This is a model used to place electrons in their shells. Bohr Diagrams 1) Find your element on the periodic table. 2) Determine the number of electrons – it is the same as the atomic number. 3) This is how many electrons you will draw. 4) The number of shells are determined by the period. Bohr Diagrams C 1) Draw a nucleus with the element symbol inside. Place Protons and neutrons in the nucleus. 2) The electrons will go in the orbits around the nucleus. Fill order of shells, 2,8,8,18. 3) Place an X over the atom. This splits the atom into quarters. Since electrons are negative and repel each other place electrons into different quarters. Clockwise! 4) Place all electrons until gone! Bohr Diagrams 1) Add the electrons. 2) Phosphorous has 15 electrons. 3) The first shell can only hold 2 electrons. Lewis Dot Structure Copy the instructions from the sheet I gave you!!!!!!! This is an easier way to draw Electrons in shells!!!! This is how you will draw atoms bonding!!!! Isotopes Atoms with the same number of protons, but different numbers of neutrons. Atoms of the same element (same atomic number) with different mass numbers Isotopes of chlorine 35Cl 37Cl 17 17 chlorine - 35 chlorine - 37 Isotopes of an element have different mass numbers because they have different numbers of neutrons, but they have the same atomic number. Learning Check AT 2 Naturally occurring carbon consists of three isotopes, 12C, 13C, and 14C. State the number of protons, neutrons, and electrons in each of these carbon atoms. 12C 6 13C 14C 6 6 #P _______ _______ _______ #N _______ _______ _______ #E _______ _______ _______ • http://www.idph.state.ia.us/eh/common/pdf/ radiological_health/radioisotopes.pdf ISOTOPIC NOTATION isotopes are atoms with the same number of protons but different number of neutrons A Z X A = mass number (the total number of protons + neutrons) Z = atomic number (the total number of protons) X = element symbol PRACTICE PROBLEMS 15N 7 # protons = ____ 8 7 # neutrons= ____ #electrons = ___ 35P 15 # p = ____ 20 # n= ____ 15 #e- = ___ 33 # n= ____ 27 #e- = ___ 62Cu2+ 29 # p = ____ 76Se3- # p = 34 ____ 42 # n= ____ 37 #e- = ___ Ways the Periodic Table is Organized 1. ELEMENTS ARE ORGANIZED IN THE PERIODIC TABLE ACCORDING TO ATOMIC NUMBER 2. ELEMENTS ARE ORGANIZED IN THE PERIODIC TABLE OF ELEMENTS ACCORDING TO THEIR SIMILAR CHARACTERISTICS • 3 major groups: metals, nonmetals and metalloids Arrangement of the Periodic table 3. Periods – Rows are called periods. The Elements in these rows have the same number of electron shells. 4. Groups – Columns are called groups. These elements have the same properties because of the number of valence electrons. Bohr Diagrams • Find out which period (row) your element is in. • Elements in the 1st period have one energy level. • Elements in the 2nd period have two energy levels, and so on. www.chem4kids.com Even though they skip some squares in between, all of the rows go left to right. When you look at a periodic table, each of the rows is considered to be a different period (Get it? Like PERIODic table.). In the periodic table, elements have something in common if they are in the same row. All of the elements in a period have the same number of electron shells. Every element in the top row (the first period) has one orbital for its electrons. All of the elements in the second row (the second period) have two orbitals for their electrons. It goes down the periodic table like that. At this time, the maximum number of electron orbitals or electron shells for any element is seven. Groups When a column goes from top to bottom, it's called a group. Groups are often called families because these elements seem to be related. **Elements in the same group show similarities in their chemical and physical properties. Valence Electrons The number of valence electrons determines how an atom will bond. The behavior of an atom is determined by its electrons. Shell Maximum Number Numb of Electrons in the Shell er 1 2 3 4 5 2x1=2 2x4=8 2 x 9 = 18 2 x 16 = 32 2 x 25 = 50 Determining the valence electrons for some elements Li – 3 electrons 2 e- in 1st level 1 e- in 2nd level 1 valence electron C – 6 electrons 2 e- in 1st level 4 e- in 2nd level 4 valence electrons Timberlake, Table 2.15 (7th Ed); Table 2.14 (8th Ed) 2.3 Elements can combine to form compounds • Compound—a substance consisting of two or more different elements combined in a fixed ratio – There are many compounds that consist of only two elements – Table salt (sodium chloride or NaCl) is an example – Sodium is a metal, and chloride is a poisonous gas – However, when chemically combined, an edible compound emerges Copyright © 2009 Pearson Education, Inc. + Sodium Chlorine Sodium Chloride Sodium Chlorine Sodium Chloride • MOLECULES ARE 2 OR MORE ATOMS ATTACHED TOGETHER – THEY CAN BE THE SAME KIND (ELEMENTS) – THEY CAN BE DIFFERENT KINDS (COMPOUNDS) Examples: H2O, NaCl. • COMPOUNDS ARE MADE OF 2 OR MORE KINDS OF ATOMS BONDED TOGETHER • FOR A COMPOUND TO FORM, A CHEMICAL CHANGE MUST TAKE PLACE (A REACTION) • THE ELEMENTS THAT COMBINE MAKE A NEW SUBSTANCE WITH NEW PHYSICAL PROPERTIES • COMPOUNDS CANNOT BE BROKEN DOWN PHYSICALLY. REQUIRES A CHEMICAL CHANGE TABLE • MORE COMMON THAN ELEMENTS NaCl SALT + = • COMPOUNDS ARE MADE OF 2 OR MORE DIFFERENT KINDS OF ELEMENTS. • COMPOUNDS ARE IDENTIFIED BY A CHEMICAL FORMULA NaCl + = TABLE SALT Chemical Changes Through Chemical Reactions A chemical reaction – Process in which the physical and chemical properties of the original substance change as new substances with different properties are formed http://www.eepybird.com/dc m1.html Chemical Formula Definition – Short way to write a compound using symbols. Subscript – Small number that is written below the element. Coefficient – The large number in front of the symbols. Counting Atoms in Compounds In compounds you will see elements and in some compound you will see small numbers behind the elements, example H2O, that small number is called a subscript. If the element does not have a subscript behind it, the subscript is 1. - The subscript tells you how many of those atoms are in that compound. . Counting Atoms in Compounds If there is a parentheses in the compound then you multiply the subscript behind the parentheses by the subscript that is behind the element in that parentheses. Ba(OH)2 – 1) In this compound there are three different elements (Barium Hydroxide) they are Barium (Ba), Oxygen (O) and Hydorgen (H). 2) In this compound the subscript 2 goes with the 4. Oxygen is in the parentheses and the two elements in the paraentheses so there parentheses are Oxygen (O) and Hydrogen (H). is 2. Same for Hydrogen. 3) Since Ba is not in the parentheses and it does not have a subscript there is one Ba. Why do elements bond? • Elements bond to fill their outer shells. This make the element stable. • Elements will either gain, lose or share electrons to fill their outer shell. Three types of Chemical Bonds • Chemically combining of two or more atoms 1. Covalent Bonds 2. Ionic Bonds 3. Hydrogen bonds These are not all the bonds but all we are going to cover. Ionic Bonds In an IONIC bond, electrons are lost or gained, resulting in the formation of IONS in ionic compounds. K F Ionic bonding Ionic bonding involves 3 steps (3 energies) 1) loss of an electron(s) by one element, 2) gain of electron(s) by a second element, 3) attraction between positive and negative Na Cl Cl– Ionization energy + e– + Na+ e– + Na+ Electron affinity Lattice energy Cl– Cl– Na+ Covalent Bonds • One or more pairs of electrons are shared by two atoms Covalent Compounds – Gases, liquids, or solids – Low melting and boiling points – Poor electrical conductors – Many soluble in nonpolar liquids but not in water Ionic Compounds – Crystalline solids – High melting and boiling points – Conduct electricity when melted – Many soluble in water but not in nonpolar liquid Octet Rule = atoms tend to gain, lose or share electrons so as to have 8 electrons C would like to Gain 4 electrons N would like to Gain 3 electrons O would like to Gain 2 electrons Single Covalent Bonds • A single covalent bond is one in which two atoms share a pair of electrons. • Structural formulas are chemical formulas that show the arrangement of atoms in molecules and polyatomic ions. – Chemical Formula • • • • H2 H2O NH3 CH4 Structural Formula H-H Electron cloud 6e– Nucleus 6 Protons 6 Neutrons 6 Electrons Mass number = 12 2.3 Elements can combine to form compounds • Many of the compounds in living organisms contain carbon, hydrogen, oxygen, and nitrogen – DNA, for example, contains all four of these elements • Interestingly, different arrangements of elements provide unique properties for each compound Copyright © 2009 Pearson Education, Inc. 2.4 Atoms consist of protons, neutrons, and electrons • Although all atoms of an element have the same atomic number, some differ in mass number – The variations are isotopes, which have the same numbers of protons and electrons but different numbers of neutrons – One isotope of carbon has 8 neutrons instead of 6 (written 14C) – Unlike 12C, 14C is an unstable (radioactive) isotope that gives off energy Copyright © 2009 Pearson Education, Inc. 2.5 CONNECTION: Radioactive isotopes can help or harm us • Living cells cannot distinguish between isotopes of the same element – Therefore, when radioactive compounds are used in metabolic processes, they act as tracers – Radioactivity can be detected by instruments • With instruments, the fate of radioactive tracers can be monitored in living organisms Copyright © 2009 Pearson Education, Inc. 2.5 CONNECTION: Radioactive isotopes can help or harm us • Biologists use radioactive tracers in research – Radioactive 14C was used to show the route of 14CO2 in formation of sugar during plant photosynthesis Copyright © 2009 Pearson Education, Inc. 2.5 CONNECTION: Radioactive isotopes can help or harm us • Radioactive tracers are frequently used in medical diagnosis • Sophisticated imaging instruments are used to detect them – An imaging instrument that uses positron-emission tomography (PET) detects the location of injected radioactive materials – PET is useful for diagnosing heart disorders and cancer and in brain research Copyright © 2009 Pearson Education, Inc. Healthy brain Alzheimer’s patient 2.5 CONNECTION: Radioactive isotopes can help or harm us • In addition to benefits, there are also dangers associated with using radioactive substances – Uncontrolled exposure can cause damage to some molecules in a living cell, especially DNA – Chemical bonds are broken by the emitted energy, which causes abnormal bonds to form Copyright © 2009 Pearson Education, Inc. 2.6 Electron arrangement determines the chemical properties of an atom • Only electrons are involved in chemical activity • Electrons occur in energy levels called electron shells – Information about the distribution of electrons is found in the periodic table of the elements Copyright © 2009 Pearson Education, Inc. Hydrogen Helium First shell Lithium Beryllium Boron Carbon Nitrogen Oxygen Fluorine Neon Sodium Magnesium Aluminum Silicon Phosphorus Sulfur Chlorine Argon Second shell Third shell 2.6 Electron arrangement determines the chemical properties of an atom • An atom may have one, two, or three electron shells – The number of electrons in the outermost shell determines the chemical properties of the atom – The first shell is full with two electrons, whereas the second and third will hold up to eight electrons Copyright © 2009 Pearson Education, Inc. 2.6 Electron arrangement determines the chemical properties of an atom • Atoms want to fill their outer electron shells – To accomplish this, the atom can share, donate, or receive electrons – This results in attractions between atoms called chemical bonds Copyright © 2009 Pearson Education, Inc. 2.7 Ionic bonds are attractions between ions of opposite charge • An ion is an atom or molecule with an electrical charge resulting from gain or loss of electrons – When an electron is lost, a positive charge results; when one is gained, a negative charge results • Two ions with opposite charges attract each other – When the attraction holds the ions together, it is called an ionic bond Animation: Ionic Bonds Copyright © 2009 Pearson Education, Inc. Transfer of electron Na Sodium atom Cl Chlorine atom Transfer of electron Na Sodium atom Cl Chlorine atom + – Na+ Sodium ion Cl– Chloride ion Sodium chloride (NaCl) Na+ Cl– 2.8 Covalent bonds join atoms into molecules through electron sharing • A covalent bond results when atoms share outer-shell electrons – A molecule is formed when atoms are held together by covalent bonds Animation: Covalent Bonds Copyright © 2009 Pearson Education, Inc. 2.9 Unequal electron sharing creates polar molecules • Atoms in a covalently bonded molecule continually compete for shared electrons – The attraction (pull) for shared electrons is called electronegativity – More electronegative atoms pull harder Copyright © 2009 Pearson Education, Inc. 2.9 Unequal electron sharing creates polar molecules • In molecules of only one element, the pull toward each atom is equal, because each atom has the same electronegativity – The bonds formed are called nonpolar covalent bonds Copyright © 2009 Pearson Education, Inc. 2.9 Unequal electron sharing creates polar molecules • Water has atoms with different electronegativities – Oxygen attracts the shared electrons more strongly than hydrogen – So, the shared electrons spend more time near oxygen – The result is a polar covalent bond Copyright © 2009 Pearson Education, Inc. 2.9 Unequal electron sharing creates polar molecules • In H2O the oxygen atom has a slight negative charge and the hydrogens have a slight positive charge – Molecules with this unequal distribution of charges are called polar molecules Copyright © 2009 Pearson Education, Inc. (–) (–) O H (+) H (+) 2.10 Hydrogen bonds are weak bonds important in the chemistry of life • Some chemical bonds are weaker than covalent bonds • Hydrogen, as part of a polar covalent bond, will share attractions with other electronegative atoms – Examples are oxygen and nitrogen • Water molecules are electrically attracted to oppositely charged regions on neighboring molecules – Because the positively charged region is always a Animation: Water Structure hydrogen atom, the bond is called a hydrogen bond Copyright © 2009 Pearson Education, Inc. Hydrogen bond WATER’S LIFE-SUPPORTING PROPERTIES Copyright © 2009 Pearson Education, Inc. 2.11 Hydrogen bonds make liquid water cohesive • Hydrogen bonding causes molecules to stick together, a property called cohesion – Cohesion is much stronger for water than other liquids – This is useful in plants that depend upon cohesion to help transport water and nutrients up the plant Copyright © 2009 Pearson Education, Inc. 2.11 Hydrogen bonds make liquid water cohesive • Cohesion is related to surface tension—a measure of how difficult it is to break the surface of a liquid – Hydrogen bonds are responsible for surface tension Animation: Water Transport Copyright © 2009 Pearson Education, Inc. Adhesion Water-conducting cells Direction of water movement Cohesion 150 µm 2.12 Water’s hydrogen bonds moderate temperature • Because of hydrogen bonding, water has a greater ability to resist temperature change than other liquids – Heat is the energy associated with movement of atoms and molecules in matter – Temperature measures the intensity of heat • Heat must be absorbed to break hydrogen bonds; heat is released when hydrogen bonds form Copyright © 2009 Pearson Education, Inc. 2.13 Ice is less dense than liquid water • Water can exist as a gas, liquid, and solid – Water is less dense as a solid, a property due to hydrogen bonding Copyright © 2009 Pearson Education, Inc. 2.13 Ice is less dense than liquid water • When water freezes, each molecule forms a stable hydrogen bond with four neighbors – A three-dimensional crystal results – There is space between the water molecules • Ice is less dense than water, so it floats Copyright © 2009 Pearson Education, Inc. Hydrogen bond Ice Hydrogen bonds are stable Liquid water Hydrogen bonds constantly break and re-form 2.14 Water is the solvent of life • A solution is a liquid consisting of a uniform mixture of two or more substances – The dissolving agent is the solvent – The substance that is dissolved is the solute Copyright © 2009 Pearson Education, Inc. 2.14 Water is the solvent of life • Water is a versatile solvent that is fundamental to life processes – Its versatility results from its polarity – Table salt is an example of a solute that will go into solution in water – Sodium and chloride ions and water are attracted to each other because of their charges Copyright © 2009 Pearson Education, Inc. Ion in solution Salt crystal 2.15 The chemistry of life is sensitive to acidic and basic conditions • A few water molecules can break apart into ions – Some are hydrogen ions (H+) – Some are hydroxide ions (OH–) – Both are extremely reactive – A balance between the two is critical for chemical processes to occur in a living organism Copyright © 2009 Pearson Education, Inc. 2.15 The chemistry of life is sensitive to acidic and basic conditions • Chemicals other than water can contribute H+ to a solution – They are called acids – An example is hydrochloric acid (HCl) – This is the acid in your stomach that aids in digestion • An acidic solution has a higher concentration of H+ than OH– Copyright © 2009 Pearson Education, Inc. 2.15 The chemistry of life is sensitive to acidic and basic conditions • Some chemicals accept hydrogen ions and remove them from solution – These chemicals are called bases – For example, sodium hydroxide (NaOH) provides OH– that combines with H+ to produce H2O (water) – This reduces the H+ concentration Copyright © 2009 Pearson Education, Inc. 2.15 The chemistry of life is sensitive to acidic and basic conditions • A pH scale (pH = potential of hydrogen) is used to describe whether a solution is acidic or basic – pH ranges from 0 (most acidic) to 14 (most basic) – A solution that is neither acidic or basic is neutral (pH = 7) Copyright © 2009 Pearson Education, Inc. pH scale 0 1 Acidic solution Increasingly ACIDIC (Higher concentration of H+) Battery acid 2 Lemon juice, gastric juice 3 Grapefruit juice, soft drink, vinegar, beer 4 Tomato juice 5 Rain water 6 Human urine Saliva NEUTRAL [H+]=OH–] 7 Pure water Human blood, tears 8 Seawater Increasingly BASIC (Lower concentration of H+) Neutral solution 9 10 Milk of magnesia 11 Household ammonia 12 Household bleach 13 Oven cleaner Basic solution 14 Acidic solution Neutral solution Basic solution 2.16 CONNECTION: Acid precipitation and ocean acidification threaten the environment • When we burn fossil fuels (gasoline and heating oil), air-polluting compounds and CO2 are released into the atmosphere – Sulfur and nitrous oxides react with water in the air to form acids – These fall to Earth as acid precipitation, which is rain, snow, or fog with a pH lower than 5.6 – Additional CO2 in the atmosphere contributes to the “greenhouse” effect and alters ocean chemistry Copyright © 2009 Pearson Education, Inc. 2.17 EVOLUTION CONNECTION: The search for extraterrestrial life centers on the search for water • An important question is, has life evolved elsewhere? – Water is necessary for life as we know it • The National Aeronautics and Space Administration (NASA) has evidence that water was once abundant on Mars – Scientists have proposed that reservoirs of water beneath the surface of Mars could harbor microbial life Copyright © 2009 Pearson Education, Inc. August 1999 September 2005 New deposit CHEMICAL REACTIONS Copyright © 2009 Pearson Education, Inc. 2.18 Chemical reactions make and break bonds, changing the composition of matter • You learned that the structure of atoms and molecules determines the way they behave – Remember that atoms combine to form molecules – Hydrogen and oxygen can react to form water 2H2 + O2 2H2O Copyright © 2009 Pearson Education, Inc. 2.18 Chemical reactions make and break bonds, changing the composition of matter • The formation of water from hydrogen and oxygen is an example of a chemical reaction • The reactants (H2 and O2) are converted to H2O, the product – Organisms do not make water, but they do carry out a large number of chemical reactions that rearrange matter – Photosynthesis is an example where plants drive a sequence of chemical reactions that produce glucose Copyright © 2009 Pearson Education, Inc. 2 H2 O2 2 H2 O Atoms have positively charged have neutral have negatively charged (b) (a) number present equals (c) number may differ in atomic number of each element number in outer shell determines formation of (d) Chemical Bonds electron transfer between atoms creates ions electron sharing between atoms creates (e) unequal sharing creates attraction between ions creates equal sharing creates nonpolar covalent bonds (g) (f) can lead to example is water has important qualities due to polarity and (h) Atoms have positively charged (a) have neutral atomic number of each element (c) (b) number may differ in number present equals (d) have negatively charged number in outer shell determines formation of Chemical Bonds electron transfer between atoms creates ions electron sharing between atoms creates (e) unequal sharing creates attraction between ions creates equal sharing creates nonpolar covalent bonds (g) (f) can lead to example is water has important qualities due to polarity and (h) Fluorine atom Potassium atom You should now be able to 1. Describe the importance of chemical elements to living organisms 2. Explain the formation of compounds 3. Describe the structure of an atom 4. Distinguish between ionic, hydrogen, and covalent bonds 5. List and define the life-supporting properties of water 6. Explain the pH scale and the formation of acid and base solutions 7. Define a chemical reaction and explain how it changes the composition of matter Copyright © 2009 Pearson Education, Inc.