Basic Chemistry Notes PDF
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These notes provide an introduction to basic chemistry concepts, including elements, atoms, protons, neutrons, electrons, atomic number, atomic mass, ions, isotopes, ionic bonds, covalent bonds, and pH scales. The notes are well-organized, and use clear language to define key concepts.
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**Basic Chemistry Notes** The **element** is the simplest form of matter. It cannot be broken down into a more simple substance. The periodic table of elements contains 120 known elements and each element has its own symbol, for instance the element Gold has the symbol Au. Elements are made of at...
**Basic Chemistry Notes** The **element** is the simplest form of matter. It cannot be broken down into a more simple substance. The periodic table of elements contains 120 known elements and each element has its own symbol, for instance the element Gold has the symbol Au. Elements are made of atoms. Atoms are made of: **Protons** -- found in the nucleus and positive in charge.\ **Neutrons** -- also found in the nucleus, but no charge. About the same size as a proton.\ **Electrons** -- found orbiting outside the nucleus and negative in charge. Very, very small. **Atomic Number** -- the number above the symbol. This tells you the total number of protons in the nucleus...and in a stable atom the number of electrons as well. **Atomic Mass** -- the number below the symbol. This tells you the sum of the protons and neutrons in the nucleus. So to find the number of neutrons just subtract the top number from the bottom. What if the number of electrons changes? You change the **charge**, but it is still the same atom. An atom with a charge other than neutral is called an **ion**. What if the number of protons changes? You change the element to a different element. What if the number of neutrons changes? You create an **isotope**. Isotopes are generally unstable and radioactive. Two or more elements bound together creates a compound. Examples would be things like H~2~O, CO~2~ or NaCl. Compounds are held together by either: 1. Ionic bonds -- which occur when one atom donates an electron to another atom to form the bond. Salt is an example. NaCl. 2. Covalent bonds -- when atoms share electrons to form the bond. Methane is an example. CH~4~ A **molecule** is the smallest functional unit of a compound. For example: H~2~O would be a single water molecule, but 5H~2~O would be five separate molecules of water. pH scale is a measure of free hydrogen ions in a solution. It is logarithmic. Every whole number increase is a factor of 10. A pH of 4 is 10 times more acidic than a pH of 5. 7 = neutral \7 = base (alkaline)
