UNIT 1: Chemistry of Life

II. THE CHEMISTRY OF LIFE (pp ) Organisms are composed of _________, which is anything that takes up space and has mass. All matter is composed of ____________, pure substances composed entirely of one type of atom and cannot be broken down by chemical reactions. A. Elements – There are ___ naturally occurring elements in nature, 25 of which are essential to life. 1. Four elements make up approx. 96% of living matter. They are: matter elements 92 Carbon (C) Carbon (C) Hydrogen (H) Hydrogen (H) Oxygen (O) Oxygen (O) Nitrogen(N) Nitrogen(N) Chemistry of Life

B.Atoms – An atom is the smallest unit of __________that still retains the properties of that __________. 1. Nucleus a. center of atom. Composed of b. _________ which have a __ charge. c. ___________ which are _________. d. overall charge of nucleus is __. Why? matter element protons+ neutronsneutral + 2. Sulfur and Phosphorus make up 3 %. These 6 elements are known as “SPONCH”. S – sulfur P – phosphorus O – oxygen N – nitrogen C – carbon H – hydrogen 3. Remaining 1% is composed of ________ ___________which are required by an organism in minute amounts. Ex. Iron (Fe), Iodine (I), Copper (Cu), Zinc (Zn) trace elements Chemistry of Life

3. 3. Charge of Atoms a. Have equal # of protons & electrons which makes the atom neutral b. __________: # of _________ that the element contains. Ex. Atomic # of carbon (C) = 6 Atomic # protons Chemistry of Life 2. Electron cloud: contains orbitals aka. __________ _______. a. area surrounding nucleus b. ___________ are in constant motion in this space. c.electrons have a __ charge; therefore attracted to the positively charged nucleus. d.The reactivity of an atom and the type of bond that it forms are determined by the number of ___________ electrons it has. electrons - electron shells valence

D. Chemical Bonds – Atoms with ______________ valence shells can interact with one another by either __________ or ______________valence electrons. The ___________ kinds of chemical bonds are covalent and ionic. incomplete sharing transferring strongest C. Compounds 1. Any substance consisting of two or more ___________ combined in a fixed ratio. 2. Held together by ___________________. elements chemical bonds Chemistry of Life