The Periodic Table of Elements

1. The Periodic Table of Elements A Brief Overview of the Patterns on the Periodic Table. Write these notes on page 15.

2. Before we get started, make sure you know: • Columns are vertical (up and down ) • Columns on the periodic table are called groups. • Rows are horizontal (side to side ) • Rows on the periodic table are called periods.

3. Elements are listed on the Periodic Table in order of increasing atomic number. • The atomic number is the number of protons in the nucleus of the atom. • Each element has a different number of protons, so the protons identify the element • ex) every atom of Carbon has 6 protons and every atom of gold has 79 protons. • The atomic number increases as you move from left to right across the periods.

4. In general, the atomic mass increases as you move from left to right on the periodic table. Can you find the exceptions? • The atomic mass represents the average mass of every atom of that particular element as it occurs in nature. • The atomic mass is the total number of protons and neutrons in the nucleus of the atom.

5. The period number represents the number of energy levels in an atom. • There are 7 periods on the periodic table. • The number of energy levels increases as you move down the periodic table.

6. Elements in the same group generally have the same number of valence electrons. • Valence electrons are electrons in the last energy level and they are important in determining the chemical properties of an element. • Because elements in the same group have the same number of valence electrons, they also have similar chemical properties. • Valence electrons increase as you move left to right.

7. Elements are grouped on the periodic table based on shared characteristics. • In general, most metals are located to the left, bottom and center of the table. • Most nonmetal elements are to the right and top of the table. • The metalloids are adjacent to a diagonal line from Boron to Astatine.