EXERCISES, LESSON 1
REQUIREMENT. The following exercises are to be answered by marking the lettered
response that best answers the question, or by completing the incomplete statement, or
by writing the answer in the space provided at the end of the question. After you have
completed all the exercises, turn to "SOLUTIONS TO EXERCISES" at the end of the
lesson and check your answers.
1. A (an) ______________ is a substance which cannot be separated into simpler
substances by ordinary chemical means.
2. It is the number of __________________ in the nucleus of an atom that
determines the element to which the atom belongs.
Two atoms of the same element with different numbers of neutrons are called