1. Which of the following is an element?
a. Water
b. Sugar
c. Salt
d. Mercury
2. Which of these substances is not an element?
a. Silicon
b. Steel
c. Sodium
d. Sulfur
3. Which of these molecules is not a compound?
c. N2
a. N2O
b. NO
d. NO2
4. Which of the following substances can be broken down further?
a. lodine
b. Calcium
c. Sodium chloride
d. Astatine
5. Which of the following is a molecule of a compound?
a. Oxygen
c. Nitrogen
b. Chlorine
d. Ammonia
answer proper ​