1. Elements & Bonding

2. I. Elements of Life A. All organisms in diverse forms are composed of matter. – 1. Matter is made up of elements; which are substances that cannot be broken down into simpler substances by chemical means.

3. I. Elements of Life B. There are 92 natural elements but 96% of mass of all organisms is made up of just 4 of them: O, C, H & N. – 1. Other elements include that make up the remaining 4% are: Ca, P, K, Mg & S – 2. Trace elements found in living organisms are: Fe, I & Cu.

4. II. Atoms A. An atom is the smallest unit that still retains the property of an element. B. The make up of an atom. – 1. Subatomic particles that make up an atom Positive protons Neutral neutrons Negative electrons

5. III. Chemical Compounds A. Chemical compound is a substance formed by the chemical combination of two or more elements in definite proportions – 1. Example: the compound water consists of one atom of oxygen and two atoms of hydrogen

6. IV. Chemical Formulas A. Chemical formulas tell you what elements a compound contains & the exact number of atoms of each element in one unit of that compound. – 1. subscripts mean “written below” tells you how many atoms of that element are in the compound. C 6 H 12 O 6 CO 2

7. V. Chemical Bonds A. The type of bonds that are made between atoms to form compounds are determined by valance electrons. – 1. Valance e⁻ are the outermost e⁻ in an atom B. Electron dot diagrams show only the electrons in the outer energy level of an atom. He NaNe

8. IV. Types of Bonds A. Atoms are only stable when they have a full valence shell. They will lose/gain or share electrons. B. The two main types of bonds are: – 1. Ionic Bonds – 2. Covalent Bonds

9. IV. Types of Bonds A. Ionic Bonds – 1. Electrons are transferred from 1 atom to another – 2. Make positive and negative ions. Written with superscripts (+, -) B. Covalent Bonds – 1. Electrons are shared between atoms – 2. Make molecules Single bond-2 e- are shared Double bond-4 e- are shared

10. Ionic Bonds – force of attraction between opposite charges of the ions. Formed usually between a metal & nonmetal Potassium & Iodine Magnesium & Chlorine Covalent bond – creates molecules sharing one or more electrons. Formed usually between 2 nonmetals. Hydrogen & Chlorine Carbon & Hydrogen

11. V. Polar Molecules A. Along covalent bonds electrons are not always shared equally. This creates polar molecules with each side being only slightly charged. (δ +, δ - ) 1. The strength of attraction between the electrons depends on the size of the positive charged nucleus & distance between nucleus.