Biomedical Science - Unit 3

Protons

+1, have a mass of about 1, and found in the nucleus. It is the atomic number.

Electrons

-1, have a mass so small we ignore it (about 0), travels around the nucleus, when an atom is neutral this number is the atomic number

Neutrons

Neutral charge, have a mass of about 1, found in the nucleus, mass number is equal to this plus the number of protons

Symbols of Elements

Chemical Formulas

Subscript to the right of the symbol of an element tells the number of atoms of that element in one molecule of the compound

Molecular Compounds

Composed of molecules

Diatomic Molecules

7 elements naturally contain two atoms: H₂, N₂, O₂, F₂, Cl₂, Br₂, I₂

Cations

Formed when at least one electron is lost, monatomic ones are formed by metals

Anions

Formed when at least one electron is gained, monatomic ones are formed by nonmetals

Writing Formulas

Molar Mass

Mass of 1 mol of a substance (g/mol or amu). It is the atomic weight for the element from the periodic table. If it is diatomic, it is twice that atomic weight.

Avogadro’s Number

In a lab, we can’t work with individual molecules because they are too small. 6.02 × 10²³ atoms or molecules is an amount that brings us to lab size and is one mole. (ex. one mole of ¹²C has a mass of 12.000 g.)

Molecular Mass

Sum of the atomic weights of the atoms in a molecule

Formula Mass

The sum of the atomic weights for the atoms in a chemical formula. What ionic compounds use.

Solutions

Homogeneous mixtures of two or more pure substances

Solvent

Component with a concentration significantly greater than the others

Solute

Component of a solution that is present at a much lower concentration than the solvent.

Aqueous Solution

When water is in the solvent

Unsaturated

Solution that has not reached its limit of solubility at a given temperature so more solute dissolves

Saturated

Solution that has reached its limit of solubility at a given temperature so no more solute dissolves

Supersaturated

Solution that has reached its limit of solubility at a given temperature and crystals may grow

Non-electrolyte

Doesn’t contain ions, bulb doesn’t light

Weak electrolytes

Contains a small amount of ions, bulb is dimly lit

Strong Electrolyte

Contains large amount of ions, bulb is brightly lit

Miscible

Substance that fully mixes in all proportions. Nonpolar solvents dissolve nonpolar solutes and polar solvents dissolve polar solutes. (ex. alcohol and water)

Immiscible

Substance that never fully mixes in any proportions (ex. oil and water)

Molarity (M)

Amount dissolved is concentration, and this is how we measure the concentration of a solution. Equation is (moles of solute)/(volume of solution in liters)

Dilution

Lower concentration, molarity of new solution determined from the equation: Mc x Vc = Md x Vd

Mass Percentage (m/m)

(Mass of solute (g))/(mass of solution (g)) x 100%

Mass/Volume Percentage (m/v)

(mass of solute (g))/ (volume of solution (mL)) x 100%