Basic Chemistry
A Atom: The smallest subdivision of a substance that still maintains the properties of that substance, frequently referred to as the building blocks of the universe. An atom is composed of the following (Figure 1-1):
1. Nucleus: Central portion of an atom, which contains protons and neutrons.
a. Proton: Positively charged particle with a mass of one atomic mass unit.
b. Neutron: Neutral particle with a mass of one atomic mass unit.
2. Electron: Negatively charged particle that revolves around the nucleus of the atom with a mass of approximately 1/1000 of an atomic mass unit. Electrons exist in well-defined orbitals that establish the chemical reactivity of an atom.
3. Normally, in its nonreactive state, an atom contains the same number of protons and electrons. The number of neutrons in the nucleus of a substance varies among atoms (isotopes).
B Element: General term applied to each of the 109 specifically named different types of atoms.
C Isotope: Atom of a substance with the same number of protons but with a varying number of neutrons. All elements have at least two isotopes. The following are the three primary isotopes of oxygen:
D Atomic weight: Average weight of an atom of a particular substance based on its comparison with the atomic weight of the carbon 12 isotope. The atomic weight is approximately equal to the sum of the number of protons and neutrons in the nucleus of an atom but is not a whole number because of the presence of isotopes (Table 1-1).
TABLE 1-1
| Element | Symbol | Atomic No. | Atomic Weight | Valence |
| Elements Commonly Seen in the Body | ||||
| Aluminum | Al | 13 | 26.98 | +3 |
| Boron | B | 5 | 10.83 | +3 |
| Calcium | Ca | 20 | 40.08 | +2 |
| Carbon | C | 6 | 12.0 | + or − 4 |
| Chlorine | Cl | 17 | 35.5 | − 1 |
| Chromium | Cr | 24 | 51.99 | − 1 or − 2 |
| Cobalt | Co | 27 | 58.93 | +2 |
| Copper | Cu | 29 | 63.55 | + 1 or +2 |
| Fluorine | F | 9 | 18.99 | − 1 |
| Hydrogen | H | 1 | 1.00 | +1 |
| Iodine | I | 53 | 126.9 | − 1 |
| Iron | Fe | 26 | 55.84 | + 1 or +2 |
| Magnesium | Mg | 12 | 24.31 | +2 |
| Manganese | Mn | 25 | 54.94 | − 2 or − 3 |
| Molybdenum | Mo | 42 | 95.94 | − 1 or − 2 |
| Nitrogen | N | 7 | 14.01 | − 3 |
| Oxygen | O | 8 | 15.99 | − 2 |
| Phosphorus | P | 15 | 30.97 | − 3 |
| Potassium | K | 19 | 39.09 | +1 |
| Selenium | Se | 34 | 78.96 | − 2 |
| Silicone | Si | 14 | 28.09 | + or − 4 |
| Sodium | Na | 11 | 22.98 | +1 |
| Sulfur | S | 16 | 32.06 | − 2 |
| Tin | Sn | 50 | 118.7 | + or − 4 |
| Vanadium | V | 23 | 50.94 | − 2 or − 3 |
| Zinc | Zn | 40 | 91.22 | + 1 or +2 |
| Other Elements Commonly Seen in Medicine | ||||
| Barium | Ba | 56 | 137.34 | +2 |
| Gallium | Ga | 31 | 69.72 | +3 |
| Helium | He | 2 | 4.00 | + or − 2 |
| Lead | Pb | 82 | 207.19 | + 1 or +2 |
| Lithium | Li | 3 | 6.94 | +1 |
| Mercury | Hg | 80 | 200.59 | + 1 or +2 |
E Gram atomic weight: Mass in grams of an element equal to its atomic weight (see Table 1-1).
F Atomic number: Equal to the number of protons in the nucleus of an atom (see Table 1-1).
G Ion: Charged species of a particular atom; occurs as a result of the loss or gain of electrons from an atom.
A Molecule: Particle that results from the chemical combination of two or more atoms normally having a neutral charge but may be positively or negatively charged.
B Compound: Molecule formed from two or more elements.
C Free radical: A charged compound, reacting as any other ion reacts.
D Molecular formula: Chemical expression indicating the types and number of atoms in a molecule. The particle that is positively charged is usually listed first.
NaCl = 1 sodium atom and 1 chloride atom contained in the molecule.
H2SO4 = 2 hydrogen atoms, 1 sulfur atom, and 4 oxygen atoms contained in the molecule.
E Molecular weight (MW): Sum total of all individual atomic weights of atoms that make up a molecule.
| Atom | No. of Atoms | Atomic Weight | Total Contributing Weight | |
| H | 2 | × | 1 | 2 |
| S | 1 | × | 32 | 32 |
| O | 4 | × | 16 | 64 |
| MW 98 |
| Atom | No. of Atoms | Atomic Weight | Total Contributing Weight | |
| C | 1 | × | 12 | 12 |
| O | 2 | × | 16 | 32 |
| MW 44 |
F Gram molecular weight (GMW): Mass in grams of a molecule equal to its MW.
G One mole of a substance is equal to one GMW of the substance.
A Valence: Number given to an atom that indicates its tendency to gain or lose electrons in a chemical reaction.
| Na+1 (sodium): | Valence of +1 indicates that in a chemical reaction it will react by losing one electrons. |
| Ca+2 (calcium): | Valence of +2 indicates that in a chemical reaction it will react by losing two electrons. |
| F−1 (fluorine): | Valence of − 1 indicates that in a chemical reaction it will react by gaining one electron. |
B Generally, valences of elements allow predictions of their chemical reactivity with each other.
C Inert gases (noble gases) have an electron distribution that has full outer orbitals. These elements (e.g., helium, neon, argon, krypton, and xenon) do not react with other elements under normal atmospheric conditions.
IV Types of Chemical Compounds
A Ionic compound: A compound formed by atoms in the compound transferring electrons, one atom gaining and the other losing electrons. Ionic compounds form ions when dissolved in solution.
| NaCl: | Na+1 has a valence of +1, and Cl−1 has a valence of − 1. The Na+1 atom has lost an electron, and the Cl− 1 atom has gained an electron during the formation of NaCl. |
| CaF2: | Ca+2 has a valence of +2, and each F−1 atom has a valence of − 1. The Ca+2 atom has lost two electrons, and each F− 1 atom has gained one electron during the formation of CaF2. |
1. Properties of ionic compounds:
c. Dissolve readily in polar solvents (solvents formed by hydrogen bonding).
d. Strong electrolytes: dissociate readily in polar solvents:
B Covalent compound: A compound formed by the sharing of electrons between the various atoms in the compound. In solution the molecule does not disassociate into its component parts.
C Hydrogen bonding (polar covalent compound): An intermediate compound between a pure covalent compound and an ionic compound characterized by an incomplete (partial) sharing of electrons. In solution the molecule only partially disassociates into its component parts.
A Synthesis reactions: Two substances react to form a third releasing energy
B Decomposition reaction: A substance breaks up into its component parts with the release of energy, normally in the form of heat.
C Exchange reaction: Two substances exchange parts to form two new substances, such as the reaction of an acid and base to form a salt and water.
VI Volume Percent and Gram Percent
A Volume percent (vol%): Method of indicating the number of milliliters of a substance in 100 ml of solution.
B Gram percent (g%): Method of indicating the number of grams of a substance in 100 ml of solution.
A Solution: Homogeneous mixture of two substances.
B Solute: Substance dissolved in a solution.
C Solvent: Substance that is the dissolving agent.
D Effects of a solute on the physical characteristics of water:
1. Solutes cause the boiling point of water to increase.
2. Solutes cause the freezing point of water to decrease.
3. The osmotic pressure of a solution containing a solute is higher than that of pure water.
E As the temperature of the solvent increases, the volume of solute that can be dissolved in the solvent also increases.
F Dilute solution: A solution with a small amount of solute dissolved in each unit of solvent at a particular temperature.
G Saturated solution: A solution with the maximum amount of solute dissolved in each unit of solvent at a particular temperature. In a saturated solution a precipitate is seen at the bottom of the solution.
H Supersaturated solution: A solution with a greater amount of solute than the solvent would normally hold, dissolved at a particular temperature. However, any physical disturbance of this solution causes the excess solute to precipitate.
I Precipitate: A crystallized solid formed at the bottom of a saturated solution.
A Ratio solution: Solution concentration represented as a ratio (1:100) between solute and solvent in number of grams to number of milliliters.
1. How many milligrams of solute are there in 1 ml of a 1:200 solution?
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2. How many milligrams are there in 5 ml of a 1:500 solution?
B Percent weight/volume (w/v): Solution concentration in which the actual percentage indicates the number of grams of solute per 100 ml of solution.
1% w/v solution means 1 g of solute is contained in 100 ml of solution.
1. How many milligrams are there in 10 ml of a 3% w/v solution?
2. How many milligrams are there in 3 ml of a 0.5% w/v solution?
C True percent solution: Solution concentration in which solute and solvent are expressed in either weight (% w/w) or volume (%v/v). The solute is expressed as a true percentage of the solution.
1. How many grams of solute are there in 250 g of a 5% w/w solution.
2. How many milliliters of solute are there in 500 ml of a 10%v/v solution.
