1. Organizing the Elements
Chapter 4 Section 2

2. Patterns in the Elements
By 1869, a total of 63 elements had been discovered.
A Russian scientists, Dmitri Mendeleev, discovered a set of patterns that applied to all the elements.
He also wrote the first periodic table.

3. Mendeleev’s Work
Mendeleev wrote each element’s melting point, density, and color on individual cards.
He also included the element’s atomic mass.
The atomic mass is the average mass of all the isotopes of an element.
Mendeleev noticed that a pattern of properties appeared when he arranged the elements in order of increasing atomic mass.

4. Periodic Table
The periodic table is a chart of the elements showing the repeating pattern of their properties.
Periodic means “in a regular, repeating pattern”

5. The Modern Periodic Table
In 1869, Mendeleev published the first periodic table.
In 1913, Henry Moseley, a British scientists, discovered a way to measure the positive charge on an atom’s nucleus.
Its atomic number

7. Organization of the Periodic Table
The properties of an element can be predicted from its location in the periodic table.
Notice that the atomic numbers increases from left to right.

9. Periods The table is organized in horizontal rows called periods.
Elements on the left side of the table are highly reactive metals.
Less reactive metals are in the middle of the table.
Next comes the metalloids, followed by the nonmetals on the right.

10. Groups
As a result of the repeating pattern of properties, the elements of the modern periodic table fall into 18 vertical columns, or groups. (sometimes known as families)
The elements within the groups have similar characteristics.

11. Reading an Element’s Square
In this book, each square includes:
the element’s atomic number
chemical symbol
name
atomic mass.

12. Latin Names of Elements
Sodium natrium = Na
Potassium kalium = K
Gold aurum = Au
Iron ferrum = Fe

13. Average Atomic Mass
The atomic mass is an average mass of all the isotopes of an element.

14. For Elements H – Ca
Element Name Element Symbol Atomic # Electron Conf