Basic Chemistry

• All matter is composed of elements
• Atomic symbol is a one- or two-letter chemical shorthand for each element, e.g., "O" for oxygen, "C" for carbon
• Four elements make up 96% of the body: C, H, O, N
• Atoms are unique building blocks for each element and give each element its particular physical & chemical properties
• Atoms are composed of protons, neutrons, and electrons
• Protons carry a positive charge (+), neutrons have no electrical charge (0), electrons carry a negative charge (-)
• Atoms of different elements are composed of different numbers of protons, neutrons, and electrons
• Atomic number is the number of protons in the nucleus, mass number is the total number of protons and neutrons in the nucleus
• Most atoms chemically combine with other atoms to form molecules and compounds
• Molecule is a general term for 2 or more atoms bonded together, compound is a specific molecule that has 2 or more different kinds of atoms bonded together
• Chemical bonds involve the electrons of reacting atoms
• Covalent bonds are formed by sharing of two or more valence shell electrons between two atoms
• Nonpolar covalent bonds involve equal sharing of electrons between atoms
• Polar covalent bonds involve unequal sharing of electrons between 2 atoms
• Hydrogen bonds are attractive forces between electropositive hydrogen of one molecule and an electronegative atom (O, N, F) of another molecule
• Solutions are homogeneous mixtures, with the solvent being the substance present in the greatest amount
• Chemical reactions occur whenever chemical bonds are formed, rearranged, or broken
• Oxidation-reduction (redox) reactions involve atoms being reduced when they gain electrons (or H atoms) and oxidized when they lose electrons (or H atoms)
• Factors influencing the rate of chemical reactions include temperature, concentration of reactants, particle size, and catalysts