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Copyright Pearson Prentice Hall

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Presentation on theme: "Copyright Pearson Prentice Hall"— Presentation transcript:

1 Copyright Pearson Prentice Hall
Biology Copyright Pearson Prentice Hall

2 Copyright Pearson Prentice Hall
2-1 The Nature of Matter Photo Credit: © John Conrad/CORBIS Copyright Pearson Prentice Hall

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Atoms Atoms The study of chemistry begins with the basic unit of matter, the atom. Copyright Pearson Prentice Hall

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Atoms Placed side by side, 100 million atoms would make a row only about 1 centimeter long. Atoms contain subatomic particles that are even smaller. Copyright Pearson Prentice Hall

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Atoms The subatomic particles that make up atoms are protons neutrons electrons Copyright Pearson Prentice Hall

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Atoms The subatomic particles in a helium atom. Helium atoms contain protons, neutrons, and electrons. The positively charged protons and uncharged neutrons are bound together in the dense nucleus, while the negatively charged electrons move in the space around the nucleus. Copyright Pearson Prentice Hall

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Elements and Isotopes Elements and Isotopes A chemical element is a pure substance that consists entirely of one type of atom. C stands for carbon. Na stands for sodium. Copyright Pearson Prentice Hall

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Elements and Isotopes The number of protons in an atom of an element is the element's atomic number. Commonly found in living organisms: Copyright Pearson Prentice Hall

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Elements and Isotopes Isotopes Atoms of the same element that differ in the number of neutrons they contain are known as isotopes. Copyright Pearson Prentice Hall

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Elements and Isotopes Because they have the same number of electrons, all isotopes of an element have the same chemical properties. Copyright Pearson Prentice Hall

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Elements and Isotopes Isotopes of Carbon Because they have the same number of electrons, these isotopes of carbon have the same chemical properties. The difference among the isotopes is the number of neutrons in their nuclei. 6 electrons 6 protons 8 neutrons Copyright Pearson Prentice Hall

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Elements and Isotopes Radioactive Isotopes Some isotopes are radioactive, meaning that their nuclei are unstable and break down at a constant rate over time Copyright Pearson Prentice Hall

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Elements and Isotopes Radioactive isotopes can be used: to determine the ages of rocks and fossils. to treat cancer. to kill bacteria that cause food to spoil. as labels or “tracers” to follow the movement of substances within an organism. Copyright Pearson Prentice Hall

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Chemical Compounds Chemical Compounds A chemical compound is a substance formed by the chemical combination of two or more elements in definite proportions. Copyright Pearson Prentice Hall

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Chemical Compounds Chemical Formula Water Table Salt Hydrochloric Acid Glucose Copyright Pearson Prentice Hall

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Chemical Bonds Chemical Bonds The atoms in compounds are held together by chemical bonds. The electrons that are available to form bonds are called valence electrons. Copyright Pearson Prentice Hall

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Chemical Bonds The main types of chemical bonds are: ionic bonds covalent bonds Copyright Pearson Prentice Hall

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Chemical Bonds Ionic Bonds An ionic bond is formed when one or more electrons are transferred from one atom to another. These positively and negatively charged atoms are known as ions. Copyright Pearson Prentice Hall

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Chemical Bonds Sodium atom (Na) Sodium ion (Cl-) Sodium ion (Na+) Sodium atom (Cl) The chemical bond in which electrons are transferred from one atom to another is called an ionic bond. The compound sodium chloride forms when sodium loses its valence electron to chlorine. Protons Electrons Charge Protons Electrons Charge Protons Electrons Charge Protons Electrons Charge Copyright Pearson Prentice Hall

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Chemical Bonds Covalent Bonds Sometimes electrons are shared by atoms instead of being transferred. Copyright Pearson Prentice Hall

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Chemical Bonds A covalent bond forms when electrons are shared between atoms. single covalent bond double bond triple bond Copyright Pearson Prentice Hall

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Chemical Bonds The structure that results when atoms are joined together by covalent bonds is called a molecule. Copyright Pearson Prentice Hall

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Chemical Bonds Van der Waals Forces When molecules are close together, a slight attraction can develop between the oppositely charged regions of nearby molecules. van der Waals forces Copyright Pearson Prentice Hall

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2-1 Copyright Pearson Prentice Hall

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2-1 The particles that move around the nucleus of an atom are called neutrons. protons. electrons. isotopes. Copyright Pearson Prentice Hall

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2-1 The atomic number of a carbon atom is 6. How many neutrons does the isotope carbon-14 have? 6 8 12 14 Copyright Pearson Prentice Hall

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2-1 Which of the following statements about the three isotopes of carbon is true? They are all radioactive. They have different numbers of electrons. They have the same chemical properties but differ in atomic mass. They have the same number of protons and neutrons. Copyright Pearson Prentice Hall

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2-1 A chemical compound consists of Electrons mixed with neutrons. two or more elements combined in a definite proportion. two or more protons combined in any proportion. at least three elements combined by ionic or covalent bonds. Copyright Pearson Prentice Hall

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2-1 Van der Waals forces are the result of unequal sharing of electrons. ionic bonds. the bonding of different isotopes. the chemical combination of sodium and chlorine. Copyright Pearson Prentice Hall

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