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HBIO 111 (23)
Chapter 2

Chapter 2 Outline: Small Molecules and Chemistry of Life

6 Pages
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Department
HBIO - Biology
Course Code
HBIO 111
Professor
Dr.Mc Cray

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Chapter 2: Small Molecules and the Chemistry of Life I. How does the atomic structure explain the properties of mater? a. All matter is composed of atoms i. Atoms= smallest unit of a chemical element 1. There is a nucleus inside each atom a. Consists of protons (+ charge) and neutrons (no charge) b. Surrounded by an electron cloud (- charge) 2. Atoms have mas and volume a. Mass is a measure of quantity of matter present; the greater the mass , the greater the quantity of matter ii. The mass of a proton serves as a SUM (stand. Unit of measure) 1. Dalton or atomic mass unit (amu) 2. Single proton or neutron has a mass of 1 dalton which is grams b. Element i. Pure substance of only one type of atom ii. Each element has specific characteristics iii. 6 essential elements for living things 1. carbon 2. hydrogen 3. oxygen 4. phosphorous 5. sulfur 6. nitrogen c. Atoms cont… i. Atomic number 1. unique to each element 2. dictates number of protons and electrons ii. Mass number 1. total number of protons and neutrons in its nucleus 2. essentially the mass of the atom in daltons iii. Dictation 1. print the atomic number in lower left and mass number in upper right a. iv. isotopes 1. different isotopes have the same number of protons but different number of neutrons 2. atomic weight a. avg of the mass numbers of a representative sample of atoms of that element with all the isotopes in their naturally occurring proportions 3. radioisotopes a. unstable and give off energy i. alpha, beta, gamma emission v. most atoms within living organisms are organized in stable associations called molecules d. Electrons i. Orbital 1. The region of space where the electron is likely to be ii. Electron shells/ energy levels 1. Electron shells a. = orbitals filled in a specific sequence in a series i. 1 shell 1. consists of just one orbital 2. called the ‘s’ orbital nd3. holds up 2 ii. 2 shell 1. comsists of 4 orbitals 2. an ‘s’ orbital and 3 ‘p’ orbitals 3. holds up 8 electrons iii. additional 1. more than 10 electrons have 3 or more shells 2. the farther a shell is from the nucleus , the higher the energy level 2. valance electrons a. outermost shell determines how atom combines with other atoms b. atoms with paired electrons are stable c. atoms with unpaired electrons are unstable, and will undergo reactions II. How do atoms bond to molecules a. Chemical bonds i. An attractive force that links two atoms together in a molecule ii. Covalent 1. Forms when two atoms attain stable electron numbers in their outermost shells by sharing one or more pairs of electrons 2. Strong bonds, takes lots of energy to break them 3. The length of a covalent bond is always the same iii. A compound 1. A substance made up of molecules with 2 or more elements bonded together in a fixed ratio 2. chemical symbols identify the different elements, and the subscript numbers indicate the number of atoms 3. molecular weight (molecular mass) a. sum of the atomic weights of all atoms in the molecule iv. Electronegativity 1. The attractive force that an atomic nucleus exerts on electrons in a covalent bond 2. sharing of bonds
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