1. Metalloids
Lesson 3, pages

2. What is a “metalloid”?
A metalloid is an element that has physical and chemical properties of both metals and nonmetals
They lie between the metals and non-metals on the periodic table, forming a zig-zag line
Silicon is the most abundant metalloid on earth – used in:
Electronic devices
Sand
Glass
Medical tubing

3. Metalloids act as “semiconductors”
Conducts electricity at HIGH temperatures, but NOT at LOW temperatures
Question: At high temperatures, is metalloid more like metal or nonmetal?
A: more like a metal because it will conduct electricity
Question: At low temperatures, is metalloid more like a metal or nonmetal?
A: more like a nonmetal because it will NOT conduct electricity
Question: Why does this property make metalloids useful in electronic devices such as computers, televisions, and solar cells?
A: When metals are used in these products, they stop conducting electricity when they get too hot so they quit working. A semiconductor will be able to continue conducting electricity at these high temperatures.

4. Other Uses of Metalloids
Boron – used in water softeners and laundry products
Boron – makes fireworks glow bright green
Silicon – sand, rocks and many minerals

5. Why is it important to know the position of elements on the periodic table?
By knowing an element’s position on the periodic table, you understand many of the properties it has. By knowing its properties, you know what it can be used for.
Question: Just from its position on the table, how do you know that sulfur would be a poor choice for making wire?
A: You know from its position that it is a non-metal so you know it would be brittle and would not conduct electricty
Question: Just from its position on the table, how do you know that iron would make a good building material?
A: You know from its position on the table that it is a transition metal and so it is strong, malleable and less reactive that other elements.