End Show Slide 1 of 40 Copyright Pearson Prentice Hall 2-1 The Nature of Matter

End Show 2-1 The Nature of Matter Slide 2 of 40 Copyright Pearson Prentice Hall Atoms Atom – smallest unit of matter Element - types of atoms. C stands for carbon. Na stands for sodium. 92 naturally occurring elements 15 found in living things 4 make up 95% of living things (C,H,O,N)

End Show 2-1 The Nature of Matter Slide 3 of 40 Copyright Pearson Prentice Hall Chemical Compounds Molecules – 2 or more atoms Compounds - two or more elements

End Show 2-1 The Nature of Matter Slide 4 of 40 Copyright Pearson Prentice Hall Atoms The subatomic particles that make up atoms are Protons Neutrons electrons

End Show 2-1 The Nature of Matter Slide 5 of 40 Copyright Pearson Prentice Hall Atoms Protons are positively charged particles (+). Neutrons carry no charge. Protons and neutrons have about the same mass. Nucleus - the center of the atom contains protons and neutrons only.

End Show 2-1 The Nature of Matter Slide 6 of 40 Copyright Pearson Prentice Hall Atoms Electrons - a negatively charged particle (−) with 1/1840 the mass of a proton. Electrons are located in energy levels around nucleus 1 st – 2 max 2 nd – 8 max 3 rd – 8 max # protons = # electrons & atoms are neutral.

End Show 2-1 The Nature of Matter Slide 7 of 40 Copyright Pearson Prentice Hall Atoms The subatomic particles in a helium atom.

End Show 2-1 The Nature of Matter Slide 8 of 40 Copyright Pearson Prentice Hall Elements and Isotopes Atomic number - The number of protons in an atom. Mass number -The sum of the protons and neutrons. ex) Carbon 12 – 6 protons & 6 neutrons

End Show 2-1 The Nature of Matter Slide 9 of 40 Elements of Life ElementAtomic Number Atomic Mass Outer electrons Electrons needed Bonds formed

End Show 2-1 The Nature of Matter Slide 10 of 40 Copyright Pearson Prentice Hall Elements and Isotopes Isotopes - Atoms of the same element that differ in the number of neutrons they contain. For example: carbon-12, carbon-13, & carbon-14.

End Show 2-1 The Nature of Matter Slide 11 of 40 Copyright Pearson Prentice Hall Elements and Isotopes Isotopes of Carbon 6 electrons 6 protons 6 neutrons 6 electrons 6 protons 7 neutrons 6 electrons 6 protons 8 neutrons

End Show 2-1 The Nature of Matter Slide 12 of 40 Copyright Pearson Prentice Hall Elements and Isotopes Radioactive Isotopes The atomic nuclei are unstable and break down at a constant rate over time. Half-life – time it takes ½ a sample to decay.

End Show 2-1 The Nature of Matter Slide 13 of 40 Copyright Pearson Prentice Hall 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.

End Show 2-1 The Nature of Matter Slide 14 of 40 Copyright Pearson Prentice Hall Chemical Compounds Chemical formula: Water, H 2 O, contains two atoms of hydrogen for each atom of oxygen. Table salt, NaCl, indicates that sodium and chlorine combine in a 1 : 1 ratio.

End Show 2-1 The Nature of Matter Slide 15 of 40 Copyright Pearson Prentice Hall Chemical Bonds Chemical Bonds: hold atoms together Covalent Bonds – sharing of electrons Single bond – share 1 pair of electrons Double bond – share 2 pairs of electrons Triple bond – share 3 pairs of electrons Polar Covalent Bond – unequal sharing of electrons Ex.) Water

End Show 2-1 The Nature of Matter Slide 16 of 40 Copyright Pearson Prentice Hall Chemical Bonds In a water molecule, each hydrogen atom forms a single covalent bond with the oxygen atom.

End Show 2-1 The Nature of Matter Slide 17 of 40 Copyright Pearson Prentice Hall Chemical Bonds Ionic Bonds - electrons are transferred from one atom to another. Ions - positively or negatively charged atoms

End Show 2-1 The Nature of Matter Slide 18 of 40 Copyright Pearson Prentice Hall Chemical Bonds Protons +17 Electrons - 18 Charge -1 Protons +11 Electrons - 11 Charge 0 Protons +11 Electrons - 10 Charge +1 Protons +17 Electrons - 17 Charge 0 Sodium ion (Cl - ) Sodium atom (Na) Sodium atom (Cl) Sodium ion (Na+)

End Show Slide 19 of 40 Copyright Pearson Prentice Hall 2-1 The particles that move around the nucleus of an atom are called a.neutrons. b.protons. c.electrons. d.isotopes.

End Show Slide 20 of 40 Copyright Pearson Prentice Hall 2-1 The atomic number of a carbon atom is 6. How many neutrons does the isotope carbon-14 have? a.6 b.8 c.12 d.14

End Show Slide 21 of 40 Copyright Pearson Prentice Hall 2-1 Which of the following statements about the three isotopes of carbon is true? a.They are all radioactive. b.They have different numbers of electrons. c.They have the same chemical properties but differ in atomic mass. d.They have the same number of protons and neutrons.

End Show Slide 22 of 40 Copyright Pearson Prentice Hall 2-1 A chemical compound consists of a.Electrons mixed with neutrons. b.two or more elements combined in a definite proportion. c.two or more elements combined in any proportion. d.at least three elements combined by ionic or covalent bonds.