Practice U2

Practice Chapter 2

Free response questions

1. Naturally occurring lead exists as four stable isotopes: with a mass of 203.973 amu (1.480%); , 205.974 amu (23.60%); , 206.9759 amu (22.60%); and , 207.9766 (52.30%). Calculate the average atomic mass of lead.

2. An average dimension for the radius of an atom is 1.0 10(8 cm, and the average radius of the nucleus is 1.0 10(13 cm. Determine the ratio of atomic volume to nuclear volume. Assume that the atom is spherical (Hint: V = r3).

3. Write isotopic notation symbols for the following:

(a) Z = 26, A = 55

(b) Z = 12, A = 26

(c) Z = 3, A = 6

(d) Z = 79, A = 188

4. The mass of an atom of argon is 6.63 10(24 g. How many atoms are in a 40.0-g sample of argon?5. Using the periodic table, determine which of the first 20 elements have isotopes that you would expect to have the same number of protons, neutrons and electrons.

6. Consider the following models of the atom: (a) Dalton, (b) Thomson (c) Rutherford. How does the location of the electrons in an atom vary? How does the location of the atoms positive matter compare?

ElementSymbolAtomic numberNumber of protonsNumber of neutronsNumber of electrons

Platinum117

5374

3618

4534

8. For each of the following compounds, indicate what is wrong with the name and why. If possible, fix the name.

(a) iron hydroxide

(b) dipotassium dichromium heptoxide

(c) sulfur oxide

9. An unidentified atom is found to have an atomic mass 7.18 times that of the carbon-12 isotope.

(a) What is the mass of the unidentified atom?

(b) What are the possible identities of this atom?

(c) Why are you unable to positively identify the element based on the atomic mass and the periodic table?

(d) If the element formed a compound M2O, where M is the unidentified atom, identify M by writing the isotopic notation for the atom._1314767124.unknown

_1314767228.unknown

_1314767928.unknown

_1314768000.unknown

_1314767363.unknown

_1314767174.unknown

_1314767065.unknown