02_LectureOutline

02_LectureOutline - Atoms Matter is made up of atoms Atoms...

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Atoms Matter is made up of atoms Atoms join together to form chemicals with different characteristics Chemical characteristics determine physiology at the molecular and cellular levels Proton Positive charge, 1 mass unit Neutron Neutral, 1 mass unit Electron Negative charge, low mass Atomic Structure Atomic number Number of protons Mass number Number of protons plus neutrons Nucleus Contains protons and neutrons Electron cloud Contains electrons Elements and Isotopes Elements are determined by the atomic number of an atom Remember atomic number = number of protons Elements are the most basic chemicals Isotopes are the specific version of an element based on its mass number Remember that mass number = number of protons plus the number of neutrons Only neutrons are different because the number of protons determines the element Atomic Weights Exact mass of all particles Measured in Daltons Average of the mass numbers of the isotopes Electrons and Energy Levels
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Electrons in the electron cloud determine the reactivity of an atom The electron cloud contains shells , or energy levels that hold a maximum number of electrons Lower shells fill first Outermost shell is the valence shell, and it determines bonding The number of electrons per shell corresponds to the number of atoms in that row of the periodic table Chemical Bonds Chemical bonds involve the sharing, gaining, and losing of electrons in the valence shell Three majors types of chemical bonds Ionic bonds : attraction between cations (electron donor) and anions (electron acceptor) Covalent bonds : strong electron bonds involving shared electrons Hydrogen bonds : weak polar bonds based on partial electrical attractions Chemical bonds form molecules and/or compounds Molecules Two or more atoms joined by strong bonds Compounds Two or more atoms OF DIFFERENT ELEMENTS joined by strong or weak bonds Compounds are all molecules, but not all molecules are compounds H 2 = molecule only H 2 O = molecule and compound Ionic Bonds One atom— the electron donor —loses one or more electrons and becomes a cation, with a positive charge Another atom— the electron acceptor —gains those same electrons and becomes an anion, with a negative charge Attraction between the opposite charges then draws the two ions together Covalent Bonds Involve the sharing of pairs of electrons between atoms One electron is donated by each atom to make the pair of electrons Sharing one pair of electrons is a single covalent bond Sharing two pairs of electrons is a double covalent bond Sharing three pairs of electrons is a triple covalent bond Nonpolar covalent bonds
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Involve equal sharing of electrons because atoms involved in the bond have equal pull for the electrons Polar covalent bonds
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02_LectureOutline - Atoms Matter is made up of atoms Atoms...

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