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Matter consists of chemical elements in pure form and in combinations called compounds Organisms are composed of matter Matter is anything that takes up.

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Presentation on theme: "Matter consists of chemical elements in pure form and in combinations called compounds Organisms are composed of matter Matter is anything that takes up."— Presentation transcript:

1 Matter consists of chemical elements in pure form and in combinations called compounds Organisms are composed of matter Matter is anything that takes up space and has mass Matter is made up of elements

2 Elements and Compounds An element is a substance that cannot be broken down to other substances by chemical reactions A compound is a substance consisting of two or more elements in a fixed ratio

3 SodiumChlorineSodium chloride

4 Essential Elements of Life Carbon, hydrogen, oxygen, and nitrogen make up 96% of living matter Most of the remaining 4% consists of calcium, phosphorus, potassium, and sulfur Trace elements are those required by an organism in minute quantities

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6 Nitrogen deficiencyIodine deficiency

7 Subatomic Particles Atoms are composed of subatomic particles – Neutrons – Protons – Electrons

8 Atomic Number and Atomic Mass Atoms of the various elements differ in number of subatomic particles Atomic Number Mass Number Neutron mass and proton mass are almost identical and are measured in daltons

9 Isotopes Atoms of an element have the same number of protons but may differ in number of neutrons Isotopes are two atoms of an element that differ in number of neutrons Radioactive isotopes decay spontaneously, giving off particles and energy

10 Carbon Isotopes

11 Some applications of radioactive isotopes in biological research: – Dating fossils – Tracing atoms through metabolic processes – Diagnosing medical disorders

12 Compounds including radioactive tracer (bright blue) Human cells Incubators 1 2 3 4 5 6 7 8 9 50ºC 45ºC40ºC 25ºC 30ºC 35ºC 15ºC 20ºC 10ºC Human cells are incubated with compounds used to make DNA. One compound is labeled with 3 H. 1 2 The cells are placed in test tubes; their DNA is isolated; and unused labeled compounds are removed. DNA (old and new) TECHNIQUE

13 Optimum temperature for DNA synthesis RESULTS Counts per minute (x 1,000) 30 20 10 0 20304050 Temperature (°C)

14 Cancerous throat tissue

15 The Energy Levels of Electrons Energy Potential energy is the energy that matter has because of its location or structure The electrons of an atom differ in their amounts of potential energy An electron’s state of potential energy is called its energy level, or electron shell

16 Electron Configuration and Chemical Properties The chemical behavior of an atom is determined by the distribution of electrons in electron shells The periodic table of the elements shows the electron distribution for each element

17 First shell Hydrogen 1 H Lithium 3 Li Second shell Third shell Sodium 11 Na Beryllium 4 Be Magnesium 12 Mg Boron 5 B Aluminum 12 Al Silicon 14 Si Carbon 6 C Nitrogen 7 N Phosphorus 15 P Oxygen 8 O Sulfur 16 S Chlorine 17 Cl Fluorine 9 F Neon 10 Ne Argon 18 Ar Helium 2 He Atomic number Element symbol Electron-shell diagram Atomic mass 2 He 4.00

18 Valence electrons are those in the outermost shell, or valence shell The chemical behavior of an atom is mostly determined by the valence electrons Elements with a full valence shell are chemically inert Each electron shell consists of a specific number of orbitals

19 The formation and function of molecules depend on chemical bonding between atoms Atoms with incomplete valence shells can share or transfer valence electrons with certain other atoms These interactions usually result in atoms staying close together, held by attractions called chemical bonds

20 Covalent Bonds A covalent bond is the sharing of a pair of valence electrons by two atoms In a covalent bond, the shared electrons count as part of each atom’s valence shell

21 Hydrogen atoms (2 H) Hydrogen molecule (H 2 )

22 A molecule consists of two or more atoms held together by covalent bonds A single covalent bond, or single bond, is the sharing of one pair of valence electrons A double covalent bond, or double bond, is the sharing of two pairs of valence electrons Covalent bonds can form between atoms of the same element or atoms of different elements

23 Number of Covalent bonds

24 Single covalent bond Double covalent bond

25 (a) Hydrogen (H 2 ) Name and Molecular Formula Electron- distribution Diagram Lewis Dot Structure and Structural Formula Space- filling Model

26 (b) Oxygen (O 2 ) Name and Molecular Formula Electron- distribution Diagram Lewis Dot Structure and Structural Formula Space- filling Model

27 (c) Water (H 2 O) Name and Molecular Formula Electron- distribution Diagram Lewis Dot Structure and Structural Formula Space- filling Model

28 (d) Methane (CH 4 ) Name and Molecular Formula Electron- distribution Diagram Lewis Dot Structure and Structural Formula Space- filling Model

29 Electronegativity is an atom’s attraction for the electrons in a covalent bond The more electronegative an atom, the more strongly it pulls shared electrons toward itself

30 H O H H2OH2O ++ ++ ––

31 In a nonpolar covalent bond, the atoms share the electron equally In a polar covalent bond, one atom is more electronegative, and the atoms do not share the electron equally Unequal sharing of electrons causes a partial positive or negative charge for each atom or molecule

32 Nonpolar Covalent Bond-bond between 2 nonmetal atoms that have the same electronegativity and therefore have equal sharing of the bonding electron pair Example: In H-H each H atom has an electronegativity value of 2.1, therefore the covalent bond between them is considered nonpolar

33 Polar Covalent Bond-bond between 2 nonmetal atoms that have different electronegativities and therefore have unequal sharing of the bonding electron pair Example: In H-Cl, the electronegativity of the Cl atom is 3.0, while that of the H atom is 2.1

34 Covalent bonds can be nonpolar or polar

35 The result is a bond where the electron pair is displaced toward the more electronegative atom. This atom then obtains a partial- negative charge while the less electronegative atom has a partial-positive charge. This separation of charge or bond dipole can be illustrated using an arrow with the arrowhead directed toward the more electronegative atom. The Greek letter delta indicates “partially”

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37 Ionic Bonds Atoms sometimes strip electrons from their bonding partners An example is the transfer of an electron from sodium to chlorine After the transfer of an electron, both atoms have charges A charged atom (or molecule) is called an ion

38 Anion - negatively charged ion Cation - positively charged ion Cations and anions are involved in biological processes, such as muscle contraction An ionic bond is an attraction between an anion and a cation

39 Sodium, potassium, and chloride ions are essential for this nerve cell to stimulate these muscle fibers

40 NaCl Na Cl Na Sodium atom Chlorine atom Cl Na + Sodium ion (a cation) Cl – Chloride ion (an anion) Sodium chloride (NaCl)

41 Compounds formed by ionic bonds are called ionic compounds, or salts Salts, such as sodium chloride (table salt), are often found in nature as crystals

42 Weak Chemical Bonds Most of the strongest bonds in organisms are covalent bonds that form a cell’s molecules Weak chemical bonds, such as ionic bonds and hydrogen bonds, are also important Weak chemical bonds reinforce shapes of large molecules and help molecules adhere to each other

43 Hydrogen Bonds A hydrogen bond forms when a hydrogen atom covalently bonded to one electronegative atom is also attracted to another electronegative atom While individually weak, hydrogen bonds are strong when present in large numbers In living cells, the electronegative partners are usually oxygen or nitrogen atoms

44 Hydrogen bonding gives water properties that help make life possible on Earth All organisms are made mostly of water and live in an environment dominated by water Water molecules are polar, with the oxygen region having a partial negative charge (  −) and the hydrogen region a slight positive charge (  ) Two water molecules are held together by a hydrogen bond

45 –– Water (H 2 O) Ammonia (NH 3 ) Hydrogen bond ++ ++ –– ++ ++ ++

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47 Van der Waals Interactions If electrons are distributed asymmetrically in molecules or atoms, they can result in “hot spots” of positive or negative charge Van der Waals interactions are attractions between molecules that are close together as a result of these charges

48 Van der Waals interactions are individually weak and occur only when atoms and molecules are very close together Collectively, such interactions can be strong, as between molecules of a gecko’s toe hairs and a wall surface

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50 Biological molecules recognize and interact with each other with a specificity based on molecular shape Molecules with similar shapes can have similar biological effects

51 Natural endorphin Endorphin receptors Brain cell Morphine (b) Binding to endorphin receptors (a) Structures of endorphin and morphine Natural endorphin Morphine Nitrogen Sulfur Oxygen Carbon Hydrogen Key

52 Natural endorphin Morphine Carbon Hydrogen Nitrogen Sulfur Oxygen Structures of endorphin and morphine

53 Natural endorphin Morphine Brain cell Endorphin receptors Binding to endorphin receptors

54 Chemical reactions make and break chemical bonds Chemical reactions lead to new arrangements of atoms The starting molecules of a chemical reaction are called reactants The final molecules of a chemical reaction are called products

55 ReactantsReactionProducts 2 H 2 OO2O2 2 H 2

56 Photosynthesis is an important chemical reaction In photosynthesis, sunlight powers the conversion of CO 2 and H 2 0 to glucose (C 6 H 12 O 6 ) and O 2

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58 Some chemical reactions go to completion: All reactants are converted to products Most chemical reactions are reversible: Products of the forward reaction become reactants for the reverse reaction Chemical equilibrium is reached when the forward and reverse reaction rates are equal

59 Animations and Videos The Chemical Basis of Life Atomic Symbols, Atomic Numbers and Mass NumbersAtomic Symbols, Atomic Numbers and Mass Numbers Electron Arrangement Electron Configurations Chemical Bonds Bond Formation Atomic Structure and Ionic Bonding

60 Ionic Bonds – 1 Ionic Bonds – 2 Covalent Bonds – 1 Covalent Bonds – 2 Transition State Bozeman - Coupled Reactions Chapter Quiz Questions – 1 Chapter Quiz Questions – 2 Animations and Videos

61 Based on the periodic table shown here, which elements will most likely form an ionic bond? Na and Cl, and Li and F C and O N and O Si and Cl all of the above

62 Based on the periodic table shown here, which elements will most likely form an ionic bond? Na and Cl, and Li and F C and O N and O Si and Cl all of the above

63 Based on the periodic table shown here, which elements will most likely form a covalent bond? Na and Cl C and O N and O Si and Cl H and H

64 Based on the periodic table shown here, which elements will most likely form a covalent bond? Na and Cl C and O N and O Si and Cl H and H

65 Titanium has an atomic number of 22. How many protons, neutrons, and electrons are in an isotope of titanium with mass number of 48? p  22, n  26, e  22 p  11, n  26, e  11 p  11, n  11, e  70 p  11, n  22, e  48 p  22, n  22, e  48

66 Titanium has an atomic number of 22. How many protons, neutrons, and electrons are in an isotope of titanium with mass number of 48? p  22, n  26, e  22 p  11, n  26, e  11 p  11, n  11, e  70 p  11, n  22, e  48 p  22, n  22, e  48

67 H 2 O can be considered ______, but H 2 can only be considered ______. an isotope and a molecule; a molecule an isotope and a molecule; an isotope a compound and an isotope; a molecule a molecule and a compound; a compound a molecule and a compound; a molecule

68 H 2 O can be considered ______, but H 2 can only be considered ______. an isotope and a molecule; a molecule an isotope and a molecule; an isotope a compound and an isotope; a molecule a molecule and a compound; a compound a molecule and a compound; a molecule

69 What do elements with atomic numbers 6, 14, and 22 have in common? same number of electrons same atomic mass same number of valence electrons and will form the same number of covalent bonds all of the above none of the above

70 What do elements with atomic numbers 6, 14, and 22 have in common? same number of electrons same atomic mass same number of valence electrons and will form the same number of covalent bonds all of the above none of the above

71 What type of bond is very prevalent in lipids and gives lipids their properties? polar covalent nonpolar covalent strong ionic weak ionic hydrogen

72 What type of bond is very prevalent in lipids and gives lipids their properties? polar covalent nonpolar covalent strong ionic weak ionic hydrogen

73 An atom of oxygen has an atomic number of 8. How many electrons are in the first, second, and third electron shells, respectively? 2, 3, 3 2, 6, 0 8, 0, 0 0, 4, 4 none of the above

74 An atom of oxygen has an atomic number of 8. How many electrons are in the first, second, and third electron shells, respectively? 2, 3, 3 2, 6, 0 8, 0, 0 0, 4, 4 none of the above

75 What numbers must be placed as coefficients in the blanks for the chemical reaction below in order to ensure that matter is conserved? 1; 1; 1 4; 3; 4 2; 1; 2 3; 4; 3 0; 3; 4 Fe 3 O 4  __C  __Fe  __CO

76 What numbers must be placed as coefficients in the blanks for the chemical reaction below in order to ensure that matter is conserved? 1; 1; 1 4; 3; 4 2; 1; 2 3; 4; 3 0; 3; 4 Fe 3 O 4  __C  __Fe  __CO

77 Of the four most commonly found elements in the human body, which has the most valence electrons? O C H N

78 Of the four most commonly found elements in the human body, which has the most valence electrons? O C H N

79 Lithium and fluorine are most likely to form which type of bond? polar covalent nonpolar covalent ionic hydrogen A and B are equally likely

80 Lithium and fluorine are most likely to form which type of bond? polar covalent nonpolar covalent ionic hydrogen A and B are equally likely

81 Carbon-14 dating works for fossils up to about 75,000 years old. Most dinosaurs went extinct 65.5 million years ago. Can 14 C be used to date dinosaur bones? Yes; the bones continued to take in 14 C, even after the dinosaur died. No; the 14 C present in the dinosaur when it died would decay too much to be measured after 65.5 million years. No; 14 C can only be used to date dinosaur teeth, which are much stronger than bones. Yes; the bones contained 14 C when the dinosaur died so it can be measured to determine the fossil’s age.

82 Carbon-14 dating works for fossils up to about 75,000 years old. Most dinosaurs went extinct 65.5 million years ago. Can 14 C be used to date dinosaur bones? Yes; the bones continued to take in 14 C, even after the dinosaur died. No; the 14 C present in the dinosaur when it died would decay too much to be measured after 65.5 million years. No; 14 C can only be used to date dinosaur teeth, which are much stronger than bones. Yes; the bones contained 14 C when the dinosaur died so it can be measured to determine the fossil’s age.

83 Radioactive uranium-235 has a half-life of 704 million years. If it was incorporated into dinosaur bones, could it be used to date the dinosaur fossils? Yes; after 65.5 million years only about one-tenth of the 235 U would have decayed, leaving plenty to measure in the fossils. No; the dinosaurs went extinct too recently to use a radioisotope with a half-life of 704 million years. No; only about one tenth of the 235 U would have decayed after 65.5 million years, not leaving enough to measure in the fossils. Yes; but only for dinosaurs that lived more than 704 million years ago.

84 Radioactive uranium-235 has a half-life of 704 million years. If it was incorporated into dinosaur bones, could it be used to date the dinosaur fossils? Yes; after 65.5 million years only about one-tenth of the 235 U would have decayed, leaving plenty to measure in the fossils. No; the dinosaurs went extinct too recently to use a radioisotope with a half-life of 704 million years. No; only about one tenth of the 235 U would have decayed after 65.5 million years, not leaving enough to measure in the fossils. Yes; but only for dinosaurs that lived more than 704 million years ago.


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