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CHAPTER 2 ACTIVE READING WORKSHEETS

CHEMISTRY OF LIFE

Section 2-1: Composition of Matter

Read the passage below, which covers topics from your textbook. Answer the questions that follow.

The central core, or nucleus, of an atom consists of two kinds of particles. One, the proton, has a positive electrical charge. The other, the neutron, has no electrical charge.

All atoms of a given element have the same number of protons. The number of protons in an atom is called the atomic number of the element.

In an atom, the number of positively charged protons is balanced by an equal number of small, negatively charged particles called electrons. The electrical charges of the electrons offset those of the protons, making the net electrical charge of an atom zero. Electrons are high-energy particles with very little mass. They move about the nucleus at very high speeds in one of several different orbitals. Electrons in outer orbitals have more energy than those in orbitals that are closer to the nucleus.

Write “P” on the line if the statement describes protons. Write “N” on the line if the statement describes neutrons. Write “E” on the line if the statement describes electrons.

SKILL: Vocabulary Development

1. The atomic number indicates how many of these an atom contains.

2. These high-energy particles have little mass.

3. These lack an electrical charge.

4. These are located in the nucleus of an atom.

5. These have a positive electrical charge.

Circle the letter of the phrase that best completes the statement.

6. The net electrical charge of an atom is zero because it contains

a. equal numbers of protons and electrons.

b. more electrons than neutrons.

c. fewer protons than electrons.

d. equal numbers of neutrons and electrons.

Original content Copyright © by Holt, Rinehart and Winston. Additions and changes to the original content are the responsibility of the instructor.

Modern Biology 7 Composition of Matter