BIOL 1441 1st Edition Exam 1 Study Guide Lectures 1 2 Chapter 2 The Chemical Context of Life I Matter a Elements and Compounds II Element Properties a Subatomic particles b Atomic number and Mass c Isotopes d Energy Level of Electrons e Electron distribution and Chemical Properties f Electron Orbitals III Chemical Bonds a Covalent bonds b Ionic bonds c Hydrogen bonds IV Structure equals Function V Chemical Reactions Lecture 1 Notes I Matter a Matter is anything that takes up space and has mass b Atom the smallest unit of matter that still retains the properties of an element i Electrons negative charge ii Protons positive charge iii Neutrons no charge c An element is something that cannot be broken down to other substances by a chemical reactions i Each element consists of certain kinds of atoms that are different from the atoms of any other elements II Element Properties a There are 92 elements on the periodic table 25 of the 92 elements are necessary for life processes b Carbon oxygen hydrogen and nitrogen make up 96 of all living matter c Trace elements elements that are required in minute quantities ex Iron and Iodine d Compounds any substance that consists of 2 or more different elements in a fixed ratio ex Water is a compound that contains 2 hydrogen and 1 oxygen i Compounds have different properties than individual elements A Subatomic Particles a Element properties depend on the structure of their atoms b The structure of the atoms depends on subatomic particles c Electrons which provide negative charge are located on the outside of the atom These notes represent a detailed interpretation of the professor s lecture GradeBuddy is best used as a supplement to your own notes not as a substitute B Atomic Number and Mass a Atomic number the number of protons in an element i An element has the same number of protons and electrons ex Sodium Na with atomic number 11 has 11 protons and 11 electrons ii All atoms of a particular element have the same number of protons in their nuclei a Changing the number of protons changes the element b Changing the number of electrons neutrons doesn t change the element Atomic mass the weight of protons plus the weight of neutrons 1 7 10 24 c Atomic nucleus center of an atom protons give the nucleus a positive charge d Dalton mass unit of an element C Isotopes a Isotopes two or more forms of the same element that contain the same number of protons but different number of neutrons in their nuclei b All isotopes have the same atomic number but differing atomic mass c Radioactive isotope isotopes in which the nucleus decays and gives off particles and energy i Radioactive isotopes are unstable d Radioactive tracers chemicals that are used to follow metabolic reactions They are injected into the blood to measure the amount of toxins in a body part ex Kidney D Energy Level of Electrons a Energy i Energy the capacity to cause change a Kinetic energy energy of movement b Potential energy energy matter possesses due to location or structure i All electrons have potential energy but the amount varies ii The amount of energy an electron contains depends on how the electrons are arranged in relation to each other and the attraction between them negative electrons are attracted to positive protons iii The further away from a nucleus an element is the more potential energy it possesses i Energy Level of Elements a Energy level the amount of potential energy an electron possesses a It correlates to the average distance from a nucleus the atom s electrons are b Shell 1 of an atom closest to the nucleus lowest potential energy c Shell 2 of an atom increased energy b When electrons move Away from the nucleus they Absorb energy c When electrons move Closer to the nucleus they Lose energy E Electron Distribution and Chemical Behavior a Electron Distribution i Shell 1 contains 1 spherical s orbital 2 electrons ii Shell 2 contains 1 spherical s orbital and a 1 p orbital 8 electrons iii Shell3 contains 8 electrons You don t need to know this for BIOL 1441 b Electron configuration determines chemical behavior of an atom i It is based on the distribution of electrons in an atom s electron shell ii Chemical behavior reactivity depends on the number of electrons in the outermost valence shell iii Valence electrons electrons in the outermost shell of an atom iv Valence the number of electrons an atom needs to fill its valence electron ex Carbon s atomic number is 6 it needs 4 valence electrons to fill its outermost shell so its valence is 4 v Atoms that have the same number of valence electrons in valence shell show the same kind of chemical behavior a Full valence shell stable unreactive chemically inactive ex Noble gases b Incomplete valence shell reactive because they want to fill their valence shells F Chemical Bonds a Atoms combine with other atoms to fill their valence shell b Bonding capacity number of covalent bonds the atom can form c 3 types of chemical bonds covalent ionic and hydrogen bonds 1 Covalent bonds sharing of a pair of valence electrons by 2 atoms This is the strongest type of bond a 4 types of covalent bonds single covalent double covalent nonpolar covalent and polar covalent i Single covalent bond a pair of shared electrons ex Hydrogen molecule ii Double covalent bond shares 2 pair of electrons ex Oxygen molecule iii Nonpolar covalent bond electrons are shared equally ex 2 atoms of the same element no charge iv Polar covalent bond bond where 1 atom is more electronegative than the other so the molecules aren t shared equally ex Oxygen and hydrogen in a water molecule b Molecule 2 or more atoms held together by a covalent bond c Compound consists of 2 or more DIFFERENT atoms ex Water molecule d Electronegativity attraction of an atom for the electrons in a covalent bond a The more electronegative an atom the stronger it pulls shared electrons to itself b Oxygen and Nitrogen are very electronegative c Carbon and hydrogen have low electronegativities d Water is a polar molecule Oxygen is very electronegative so electrons spend more time around the oxygen than the hydrogen e Non polar bonds O O N N C C H H 2 atoms of the same electronegativity are non polar f Polar bonds O C O H N C N H 2 atoms of different electronegativities 2 Ionic bonds a Ionic bonds an attraction between 2 oppositely charges molecules or atoms ex A bond between Na and Cl i The more electronegative atom strips an electron completely away from another atom making it an ion ii Ion a