Unit 2- Materials: Structure and Uses. Unit 2- Materials: Structure and Uses. Section 2. A – Why we use what we do. Do Now. Read pages. 108-109. Objectives. 1. Define properties and changes. 2. Distinguish between physical and chemical changes and classify examples of each.
Section 2. A –
Why we use what we do
A.4 Supplement handout
A.7: Grouping the Elements
Refer to the periodic table to identify the elements and atomic numbers (number of protons).
In electrically neutral atoms (no charge) the number of positively charged protons equals the number of negatively charged electrons.
Mass Number– equal to the total number of protons plus the total number of neutrons.
Refer to periodic table on page 124
A major difference between metals and nonmetals is that metals lose electrons while nonmetals gain electrons.
Some physical properties of metals depend on the attractions among their atoms.
Chemical and physical properties of nonmetals also depend on the attractions among their atoms.
Understanding the properties of atoms is the key to predicting the behavior of materials.
What would make the best material for a new coin: a metal, nonmetal or metalloid?