1. The Modern Periodic Table
Physical Science

2. The Periodic Table Organizing the elements
Until 1750, scientists had identified only 17 elements. Lavoisier grouped them into metals, nonmetals, gases, and earths.

3. Mendeleev
Mendeleev arranged the elements in rows in order of increasing mass with elements with similar properties in the same column.

4. Mendeleev was not the first to arrange elements in a periodic table.
He was not the first to leave spaces for missing elements.
He had the best explanation for how the properties of an element related to its location in the table.

5. Evidence Supporting Mendeleev’s Table
He predicted there would be an element one space below AL on the table – it would be soft, low melting point, and density of 5.9 g/cm3.
Then, 10 years later, Gallium was discovered. It had a density of 5.91 g/cm3 and a melting point of 29.7 C.

6. The Modern Periodic Table
Periods – each row is a period
Groups – each column is a group. Elements within a group have similar properties.
**Electron configuration determines an element’s chemical properties.

7. Classes of Elements Solid, liquid, or gas Natural or man-made
Metal, non-metal, metalloid

8. Metals
Metals are good conductors of heat and electric current. They are solid at room temperature (exc. Hg). Most are malleable and ductile.

9. Nonmetals Nonmetals are poor conductors of heat and electric current.
Most are gas at room temperature.
The few that are solid are brittle.

10. Metalloids
Metalloids are elements with properties that fall between those of metals and nonmetals.
For example, a metalloid’s ability to conduct electric current varies with temperature.

11. Variation Across a Period
Across a period from left to right, the elements become less metallic and more nonmetallic.