Inquiry into Life Twelfth Edition Chapter 2 Lecture PowerPoint to accompany Sylvia S. Mader Copyright The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 2.1 Basic Chemistry Matter is anything that takes up space and has weight. 2.1 Basic Chemistry Energy is the ability to do work. Matter is anything that takes up space and has mass. Matter and Energy can be exchanged, but cannot be destroyed. All matter, living or nonliving, is made up of elements. 2.1 Basic Chemistry Elements are substances that cannot be broken down to simpler substances with different properties. Elements that make up the Earths crust and its organisms. Elements that make up 95% of living organisms (by weight) CCarbon Elements that make up 95% of living organisms (by weight) CCarbon HHydrogen Elements that make up 95% of living organisms (by weight) CCarbon HHydrogen NNitrogen Elements that make up 95% of living organisms (by weight) CCarbon HHydrogen NNitrogen OOxygen Elements that make up 95% of living organisms (by weight) CCarbon HHydrogen NNitrogen OOxygen PPhosphorus Elements that make up 95% of living organisms (by weight) CCarbon HHydrogen NNitrogen OOxygen PPhosphorus SSulfur Atomic Structure Atom : The smallest part of an element that displays the properties of the element. Atoms are made up of subatomic particles. Subatomic Particles Protons (positively charged) Subatomic Particles Protons (positively charged) Neutrons (uncharged) Subatomic Particles Protons (positively charged) Neutrons (uncharged) Electrons (negatively charged) Helium Atomic Symbol C 12 6 Atomic Mass Atomic Number Carbon Atomic Symbol Atomic Mass = Number of Protons + Number of Neutrons Atomic Number = The Number of Protons in the Nucleus The Periodic Table Isotopes C C C * *radioactive Atoms of the same element with a differing numbers of neutrons Radiation As radioactive isotopes decay, energy is released in the form of subatomic particles (radiation). Some Uses of Low Levels of Radiation Some Uses of High Levels of Radiation Electrons If an atom is electrically neutral, the number of protons (positively charged) is equal to the number of electrons (negatively charged). Energy Levels (electron shells) The first shell (closest to the nucleus) can contain two electrons Energy Levels (electron shells) The first shell (closest to the nucleus) can contain two electrons Each additional shell can contain eight electrons Energy Levels (electron shells) The first shell (closest to the nucleus) can contain two electrons Each additional shell can contain eight electrons Each lower shell is filled with electrons before the next higher level contains any electrons. Periodic Table (Revisited) Vertical columns indicate number of electrons in outermost shell 1 H Li Na K Be Mg Ca B Al Ga C Si Ge N P As O S Se F Cl Br Ne Ar Kr He Horizontal periods indicate total number of electron shells I II IIIIV V VI VII VIII Electrons Atoms can give up, accept, or share electrons to have eight electrons in the outer shell. 2.2 Elements and Compounds Molecules usually form when two or more atoms bond together by forming covalent bonds (example: O 2 ) A molecule is the smallest particle of matter that can have independent existence: He, Ne, H 2, N 2, O 2, Cl 2, CO 2, H 2 O, NH 3, CH 4 2.2 Elements and Compounds Molecules form when two or more atoms bond together by forming covalent bonds (example: O 2 ) Compounds form when two or more different elements bond together (example: H 2 O) 2.2 Elements and Compounds Molecules form when two or more atoms bond together (example: O 2 ) Compounds form when two or more different elements bond together (H 2 O) When a chemical reaction occurs, energy may be given off or absorbed. Ionic Bonding Ions are charged particles that form when electrons are transferred from one atom to another. Ionic Bonding Ions are charged particles that form when electrons are transferred from one atom to another. Ionic compounds are held together by an attraction between oppositely charged ions called an ionic bond. Ionic Bonding Covalent Bonding In covalent bonds, atoms share electrons allowing each atom to have a completed outer shell. Covalent Bonding A covalent bond A double covalent bond Shape of Molecules Nonpolar covalent bonds If the sharing between two atoms is fairly equal, the covalent bond is described as nonpolar. Polar Covalent Bonds If the sharing between two atoms is unequal, the covalent bond is described as polar. Hydrogen Bonding A hydrogen bond occurs between a slightly positive hydrogen atom of one molecule and a slightly negative atom of another molecule, or between atoms of the same molecule.