Mr. Bouyer

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This Week's

Mendeleev Moseley Periodic Law Group Family Period	Metal Alkali metals Alkaline earth metals Transition metals Rare-earth metals Nonmetal Halogens	Noble gases Metalloid Valence Chemical activity Electron energy level Electron energy sublevel

Dmitri Mendeleev: A Russian chemist in the mid-1800s. Mendeleev cataloged thousands of facts about the 63 elements known at the time. He became convinced that groups of elements had similar, "periodic" properties. Elements on Mendeleev's table were arranged according to their increasing atomic mass, leaving blank spaces where he was sure other, unknown elements would fit. He was so bold as to predict the properties of these unknown elements based on the idea of periodic properties. Because of this, Mendeleev is considered to be the Father of the Periodic Table.

Fifty years after Mendeleev, the British scientist Henry Moseley discovered that the number of protons in the nucleus of a particular type of atom was always the same. When atoms were arranged according to increasing atomic number, the few problems with Mendeleev's periodic table disappeared. Because of Moseley's work, the modern periodic table is based on the atomic numbers of the elements.

Science Teacher

The Periodic Law: The physical and chemical properties of the elements are periodic functions of their atomic numbers.

The modern periodic table has elements arranged in a series of: Vertical columns called groups or families Horizontal rows called periods

Groups on the periodic table:

Groups are numbered from left to right on the table - 1 to 18

Elements in groups have similar properties. That is why they are called families.

Although the properties are similar, they change as you go up or down the group. For example, chemical activity generally increases as you go down a metal group and decreases as you go down a nonmetal group.

Periods are numbered from top to bottom on the table - 1 to 7

The properties of elements in a period are quite different, but there are patterns.
• The first (far left) element in a group is always an active metal, the last (far right) is always an inactive nonmetal.
• Generally, within a period, the chemical activity of metals increases from right to left, while the chemical activity of nonmetals in a period increases from left to right. Chemicals are broken down and changed when a more reactive element displaces a less reactive element in a compound.

• The shape of the periodic table has changed several times through the years as our understanding of the atom has improved.

A wealth of chemistry information can be read directly from the periodic table. The better you understand the shape, the more you can read.

In-Class Assignment 091:
This assignment must be turned in by the end of class today to receive credit.
Scoring criteria

1. Ask your teacher for a printed copy of this Periodic Table.
2. Use the table to do the following:
   1. Circle the most active metal on row four of the table.
   2. Circle the inactive nonmetal on row six of the table.
   3. Circle the most active element in group 1.
   4. Circle the most active element in group 17.
   5. Draw the line that separates metals from nonmetals on your table.
3. Answer these questions below the periodic table.
   1. How was Mendeleev's table arranged?
   2. How was Moseley's table arranged?
   3. Is your table arranged like Mendeleev's or Moseley's?
   4. Write the names of the ten families of elements on the periodic table.
   5. To the right of each family name, write the number of electrons in the outer energy of the atoms in the family.

   Information for question 3 is on tomorrow's notes page.

Physical Science

There are 18 vertical columns, Groups, on today's periodic table.