Basic Chemistry

Element Substances made entirely of one kind of atom: can’t be broken down into simpler substances (114 identified)

K:\Biochemistry\Tom Lehrer's The Elements_ A Flash animation by Mike Stanfill, Private Hand.mht

Atoms Each element is made of atoms, which are the building blocks of matter Atoms are the smallest part of an element that have the properties of that element

Most Common Elements in Living Things Carbon Hydrogen Oxygen Nitrogen Smaller quantities of the elements: sulfur, phosphorus, magnesium, iodine, iron, calcium, sodium, chlorine and potassium

Compounds A substance composed of 2 or more elements that are chemically combined in definite proportions Examples: water (H2O) carbon dioxide (CO2) sodium chloride (NaCl) glucose (C6H12O6)

Symbols Letters are used to represent elements Examples :Na, O, Cl, C, H etc

Formulas Are used to represent compounds Chemical Formulas: use letters to represent the elements and subscripts to show how many atoms of each element are present ex: C6H12O6 glucose H2O water CO2 carbon dioxide

Formulas Structural Formulas: show the number and kinds of atoms and how they are bonded together Ex: glucose

Atomic Structure Nucleus in the center, containing neutrons and protons and electrons travel around the nucleus in paths called orbits Protons have a positive charge Electrons have a negative charge Neutrons have a neutral charge

Atomic number = the number of protons in the nucleus of an atom, the number identifies the element (also tells the number of electrons) Atomic mass (mass number) = the number of protons + the number of neutrons

Isotopes Atoms that differ from other atoms of the same element by the number of neutrons in the nucleus (have the same number of protons and electrons) Ex: hydrogen has 3 isotopes – all have 1 proton but each has a different # of neutrons)

Covalent Bonds Elements combine by sharing electrons Ex: water, chlorine, oxygen

Ionic Bonds The force of attraction between 2 ions in a chemical compound Elements combine by transferring electrons EX: sodium chloride

Chemical Reactions The process in which chemical bonds are broken and the atoms form new bonds, producing new substances C6H12O6 + 6O2  6CO2 + 6H2O Glucose + Oxygen  carbon dioxide + water

Reactants The substances that were present before a reaction started C6H12O6 + 6O2  6CO2 + 6H2O The reactants in this equation are glucose and oxygen

Products The new substances produced by the chemical reaction C6H12O6 + 6O2  6CO2 + 6H2O The products of this reaction are carbon dioxide and water

Acids and Bases An acid is any compound that produces hydrogen ions in solution Examples: HCl – hydrochloric acid

Acids and Bases A base is a compound that produces hydroxide ions when dissolved in water Ex: NaOH – sodium hydroxide

Neutralization Reactions The reaction of an acid with a base to produce a neutral solution A neutralization reaction produces water and a salt as products Ex: HCl + NaOH  NaCl + H2O Hydrochloric acid + sodium hydroxide  salt + water

Acids and Bases Substances can be classified as acids or bases based on their pH. Acids have a pH from 1 to 6 Bases have a pH from 8 to 14 A pH of 7 is neutral

Indicators Indicators are substances that change color and identify a substance as an acid or a base Ex: Litmus paper (red and blue) Red in acid , blue in base Phenolpthalein colorless to pink in a basic solution Methyl Orange -yellow to red in acid