Chemical+Context+of+Life

=Chapter 2. The Chemical context of Life.=

Objectives:

 * 1) Matter consits of chemical elements in pure form and in combinations called compounds.
 * 2) Life requires about 25 chemical elements.
 * 3) Atomic structure determines that behavior of an element.
 * 4) Atoms combine by chemical bondig to form molecules.
 * 5) Weak chemical bonds play important roles in the chemistry of life.
 * 6) A molecule's biological function is related to its shape.
 * 7) Chemical reactions make and break chmical bonds.

Vocabulary

 * **Matter**- anything that takes up space and has mass.
 * **Element**- a substance that cannot be broken down to other substances by chemical reactions.
 * **Compund**- a substance consisting of two or more elements combined in a fixed ratio (ex: table salt).
 * **Trace elements**- elements required by an organism in only minute quanities.
 * **Protons-** a stable, positively charged subatomic particle.
 * **Nuetrons-** an electrically neutral subatomic particle.
 * **Electrons-** a stable subatomic particle, with a negative electric chrage.
 * **Atomic nucleus**- tightly packed nuetrons and protons to form a dense core at the center of the atom.
 * **Dalton**- the unit of measurement used for atoms and subatomic particles.
 * **Atomic number**- the number of protons which is unique to that element.
 * **Mass number**- the sum of protons and neutrons in the nucleus of an atom.
 * **Atomic weight**- the approximation of the total mass of the atom.
 * **Isotopes**- the different atomic forms of an element.
 * **Radioactive isotopes**- the nucleus decays spontaneously, giving off particles of energy.
 * **Energy**- the ability to do work.
 * **Potential engergy**- the energy that matter stores because of its postion or location.
 * **Energy levels, or electron shells**- the different states of potential energy for electrons in an atom.
 * **Orbital-** the three-dimensional space where an electron is found 90% of the time.
 * **Valence electrons-** the outer electrons.
 * **valence shells-** the outermost electron shell.
 * **Chemical bonds-** atoms with incomplete valemce shells interact with certain other atoms in such a way that each partner completes its valence shell.
 * **Covalent bonds-** the sharing of a pair of valence electrons by two atoms.
 * **Molecule-** two or more atoms held together by a covalent bond.
 * **Structural fomula-** the notation that represents both atoms and bonding.
 * **Molecular formula-** a chemical formula that shows the number and kinds of atoms in a molecule.
 * **Double covalent bond- a** covalent bond in which two electron pairs are shared between two atoms.
 * **Valence- t**he combining capacity of an atom or radical determined by the number of electrons that it will lose, add, or share when it reacts with other atoms.
 * **Electonegativity-** the attraction of an atom for the electrons of a covalent bond.
 * **Nonpolar covalent bonds-** the electrons are shared equally.
 * **Polar covalent bonds-** if one atom is more electronegative than the other, electrons of the bond will not be shared equally.
 * **Ion-** a charged atom or molecule.
 * **Cation-** when the ion is positivly charged.
 * **Anion-** when the ion is negativly charged.
 * **Ionic bond-** when cations and anions attract each other.
 * **Hydrogen bond-** when a hydrogen atom covalently bonded to one electronegative atom is also attracted to another electronegative atom.
 * **Van der Waals interactions-** a class of intermolecualr forces which arise from the polarization of molecules into dipoles.
 * **Reactants-** a substance participating in a chemical reaction, especially a directly reacting substance present at the initiation of the reaction.
 * **Products-** a substance that forms as a result of chemical reaction.
 * **Chemical equilibrium-** the point at which the reactions offset one another exactly.

Important Content
Objective 1: Objective 2: Objective 3: Objective 4: objective 5: Objective 6: Objective 7:
 * Matter exists in many diverse forms, each with its own characteristcis.
 * Substances are formed by blending various porportions of two or more elements together.
 * There are 92 elements that occur in nature.
 * Compounds have 1:1 ratios.
 * About 25 or the 92 natural elements are essential to life.
 * C, O, H, N make up 94% of living matter, P, S, Ca, K make up the rest of the 4 %.
 * Atoms are so small that it would take about a million of them to stretch across the period printed at the end of this sentence.
 * Physicists have split the atom into more than a hundred types of particles.
 * Electrons and protons are electrically charged.
 * Electron shells closest to the nucleus have the lowest energy.
 * An atom with a complete valence shell is unreactive.
 * Chemical bonds. (above)
 * Covalent bonds. (above)
 * Nonpolar/ Polar covalent bonds. (above)
 * Ion, Cation. (above)
 * Covalent bonds are essential to life becasue they link atoms to form a cell' s molecules.
 * Chemical signaling is an exaple of the importance of weak bonding.
 * The hydrogen bond is crucial to life.
 * Hydrogen bond. (above)
 * Van der Waals interactions. (above)
 * The shape of an atom is determinded by the position of an atoms' orbitals.
 * Products. (above)
 * Reactants. (above)
 * Chemical equalibrium. (above)

Helpful diagrams:
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Ionic bond: