Chemistry review chapter 3

a. the law of conservation of mass b. the law of definite proportions c. the law of multiple proportions

1. a. Because all chemical reactions are only the rearrangements of atoms, mass is neither created nor destroyed in such changes. b. Atoms of each element have their own characteristic mass, so compounds consisting of these atoms always have the same composition by mass. c. Only whole atoms combine in chemical compounds, so different compounds between the same two elements must result from the combination of different whole numbers of atoms.

10. What is a nuclide?

10. any isotope of any element

12. a. What nuclide is used as the standard in the relative scale for atomic masses? b. What is its assigned atomic mass?

12. a. carbon-12 b. exactly 12 u

13. What is the atomic mass of an atom if its mass is approximately equal to the following? a. _1 that of carbon-12 3 b. 4.5 times as much as carbon-12

13. a. 4 u b. 54 u

14. a. b. What is the abbreviation for mole? c. How many particles are in one mole? d. What name is given to the number of particles in a mole? What is the definition of a mole?

14. a. the number of particles equal to the number of atoms in exactly Untitled-62 86 12 g of carbon-12 b. mol c. 6.022 × 1023 d. Avogadro's number

2. According to the law of conservation of mass, if element A has an atomic mass of 2 mass units and element B has an atomic mass of 3 mass units, what mass would be expected for compound AB? for compound A2B3?

2. 5 mass units; 13 mass units

4. Describe at least four properties of electrons that were determined based on the experiments of Thomson and Millikan.

4. An electron is negatively charged, has a mass approximately 1/2000 that of a hydrogen atom, has a fixed charge-to-mass ratio, and is present in atoms of all elements.

5. Summarize Rutherford's model of the atom, and explain how he developed this model based on the results of his famous gold-foil experiment.

5. His model had most of the mass in the nucleus. He bombarded gold atoms with positively charged particles; most went straight through the atom, but some were deflected and a few bounced back.

6. What number uniquely identifies an element?

6. the atomic number

7. A. What are isotopes? B. How are the isotopes of a particular element alike? C. How are they different?

7. a. atoms of an element that have the same number of protons but a different number of neutrons b. They have the same number of protons and electrons. c. They have different numbers of neutrons.

3. a. What is an atom? b. What two regions make up all atoms?

A. the smallest particle of an element that retains the chemical properties of that element b. the nucleus and the surrounding region of electrons

8. Copy and complete the following table concerning the three isotopes of silicon, Si. (Hint: See Sample Problem A.) Isotope Number of protons Number of electrons number of neutrons Si-28 Si-29 Si-30

IsotopeProtonsElectronsNeutrons Si-28 14 14 14 Si-29 14 14 15 Si-30 14 14 16

11. Use the periodic table and the information that follows to write the hyphen notation for each isotope described. a. atomic number = 2, mass number = 4 b. atomic number = 8, mass number = 16 c. atomic number = 19, mass number = 39

a. helium-4 b. oxygen-16 c. potassium-39

9. a. What is the atomic number of an element? b. What is the mass number of an isotope? c. In the nuclear symbol for deuterium, 21H, identify the atomic number and the mass number.

a. its number of protons b. the total number of protons and neutrons in an isotope c. atomic = 1, mass = 2