**11. an isotope has the same number of:**\na) protons but a different number of electrons\nb) electrons but…

**11. an isotope has the same number of:**\na) protons but a different number of electrons\nb) electrons but a different number of protons\nc) neutrons but a different number of electrons\nd) protons but a different number of neutrons\n\n**12. which of the following represents a chemical formula?**\na) all of the above\nb) co2\nc) nacl\nd) h2o\n\n**13. in a chemical reaction, the substances present before the reaction takes place are called:**\na) reactants\nb) solvents\nc) products\nd) catalysts

**11. an isotope has the same number of:**\na) protons but a different number of electrons\nb) electrons but a different number of protons\nc) neutrons but a different number of electrons\nd) protons but a different number of neutrons\n\n**12. which of the following represents a chemical formula?**\na) all of the above\nb) co2\nc) nacl\nd) h2o\n\n**13. in a chemical reaction, the substances present before the reaction takes place are called:**\na) reactants\nb) solvents\nc) products\nd) catalysts

Answer

Brief Explanations:

  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