Question

11. an isotope has the same number of:
a) protons but a different number of electrons
b) electrons but a different number of protons
c) neutrons but a different number of electrons
d) protons but a different number of neutrons

12. which of the following represents a chemical formula?
a) all of the above
b) co2
c) nacl
d) h2o

13. in a chemical reaction, the substances present before the reaction takes place are called:
a) reactants
b) solvents
c) products
d) catalysts

Explanation:

1. Isotopes are atoms of the same element with the same number of protons but different numbers of neutrons.
2. CO2, NaCl, and H2O are all chemical formulas representing carbon - dioxide, sodium chloride, and water respectively.
3. In a chemical reaction, the substances present before the reaction are reactants.

Answer:

1. d) Protons but a different number of neutrons
2. a) All of the above
3. a) Reactants