A. Grouping

1. Columns are called groups

a. Group A are the main group elements (aka representative elements) and Group B are the transitional elements

2. Rows are also known as periods and correspond to rows of electrons

3. A groups

a. 1A - alkali metals

b. 2A - alkaline earth metals

c. 7A - halogens

d. 8A - noble gases (the most stable elements)

4. Lanthanides and actinides are subfolders within the 6th and 7th periods

B. Numbers

1. Atomic numbers are the values above the element symbol

2. Atomic mass is represented by the values underneath each element symbol

A. Atomic structure

1. Atoms consist of only 3 atomic particles: electrons, protons and neutrons (protons and neutrons make up the nucleus while electrons orbit)

B. Atomic particle information

1. Symbols: p^+ for protons, n^0 for neutrons and e^- for electrons

2. Charges: +1 for protons, 0 for neutrons and -1 for electrons

3. Mass: 1 amu for protons, 1 amu for neutrons and 1/2000 amu for electrons

A. Nuclear symbol - the notation that displays an element symbol with its mass number to the top left and the atomic number to the bottom left

B. Elements differ due to the numbers of protons, neutrons and electrons present

A. Isotopes - atoms of the same element that have different numbers of neutrons present in the nucleus

B. Atomic mass unit (amu)

1. 1 amu is equal to 1/12 of the mass of a carbon-12 atom

2. Average relative atomic mass = ((mass of the first isotope)(% as decimal natural abundance))+((mass of isotope 2)(natural abundance))