Chapter 2: Atoms, Molecules, and Ions

Show all work, units, and sig figs when answering the following.

1.  You have a chemical in a sealed glass container filled with air. The setup is sitting on a balance as shown below. The chemical is ignited by means of a magnifying glass focusing sunlight on the reactant. After the chemical has completely burned, which of the following is true? Explain your answer.

a.  The balance will read less than 250.0g

b.  The balance will read 250.0 g

c.  The balance will read greater than 250.0g

d.  Cannot be determined with knowing the identity of the chemical

2.  Dalton assumed that all atoms of the same element were identical in all their properties. Explain why this assumption is not valid.

3.  Draw all possible structural formulas of a compound with molecular formula, C5H12 by initially changing how the carbons are attached to each other. These different forms of the same compound are called isomers.

4.  Roughly speaking, the radius of an atom is about 10,000 times greater than that of its nucleus. If an atom were magnified so that the radius became 2.0 cm, about the size of a marble, what would the radius of the atom be in miles (1 mi = 1609 m)

5.  Do the proton and the neutron have exactly the same mass? How do the masses of the proton and the neutron compare to the mass of the electron? Which particles make the greatest contribution to the mass of an atom? Which particles make the greatest contribution to the chemical properties of an atom?

6.  Distinguish between the terms family and period in connection with the periodic table. For which of these is the term group also used?

7.  The two most reactive families of elements are the halogens and the alkali metals. How do they differ in their reactivity? Specify. Where are the most reactive metals? Non-metals? What contributes to their ability to be classified as reactive? Discuss in terms of periodic trends and use appropriate terms to support your claims (i.e. shielding, energy levels, electronegativity, coulombic attraction, etc.)

8.  In the periodic table, how many elements are found in

  1. Group 2A? c. The nickel group?
  2. The third period? d. Group 8A?

9.  How many protons and neutrons are in the nucleus of each of the following atoms? In a neutral atom of each element, how many electrons are present?

  1. 79Br d. 133Cs
  2. 81Br e. 3H
  3. 239Pu f. 56Fe

10.  Write the nuclide symbol for each of the following isotopes.

  1. Z=8, number of neutrons=9
  1. The isotope of chlorine in which A=37
  1. Z=27, A=60
  1. Number of protons=26, number of neutrons = 31
  1. The isotope of I with a mass number of 121
  1. Z=3, number of neutrons=4

11.  Use the following mass spectroscopy data to calculate the average atomic mass of the element. Identify the element.

12.  For each of the following sets of elements, label each as noble gases, halogens, alkali metals, alkaline earth metals, or transition metals.

  1. Ti, Fe, Ag d. Ne, Kr, Xe
  2. Mg, Sr, Ba e. F, Br, I
  3. Li, K, Rb

13.  What is the trend in metallic character going from left to right across a period in the periodic table?

14.  Would you expect each of the following atoms to gain or lose electrons when forming ions? What ion is most likely in each case?

  1. Ra c. P e. Br
  2. In d. Te f. Rb

15.  Name each of the following compounds:

  1. Hg2O c. CoS
  2. Rb2O d. AII3

16.  Name each of the following compounds:

  1. BaSO3 c. Al2(SO4)3
  2. NaNO2 d. K2Cr2O7

17.  Name each of the following compounds:

  1. CuI f. S4N4
  2. CuI2 g. SF6
  3. CoCI2 h. NaOCl
  4. Na2CO3 ∙ 10 H2O i. BaCrO4
  5. NaHCO3 j. NH4NO3

18.  Write the formula for each of the following compounds:

  1. Sulfur difluoride
  1. Sulfur hexafluoride
  1. Sodium dihydrogen phosphate
  1. Lithium nitride
  1. Chromium(III) carbonate
  1. Tin(II) fluoride
  1. Ammonium acetate
  1. Ammonium acetate
  1. Ammonium hydrogen sulfate
  1. Cobalt(III) nitrate
  1. Mercury(I) chloride

19.  Write the formula for each of the following compounds:

  1. Ammonium hydrogen phosphate
  1. Mercury(I) sulfide
  1. Silicon dioxide
  1. Sodium sulfite
  1. Aluminum hydrogen sulfate
  1. Nitrogen trichloride
  1. Hydrobromic acid
  1. Bromous acid
  1. Perbromic acid
  1. Potassium hydrogen sulfide
  1. Calcium iodide
  1. Cesium perchlorate

20.  Technetium (Tc) was the first synthetically produced element. Technetium comes from the Greek word for “artificial”. It was first produced by Perrier and Segre in 1937 in Berkeley, California, by bombarding a molybdenum plate with 2H nuclei. Elemental technetium is produced from ammonium pertechnetate. How many protons and neutrons are in the nuclei of 98Tc and 99Tc? What is the formula of ammonium pertechnetate? Tc was missing from Mendeleev’s periodic table, yet he acknowledged its possible existence. What did Mendeleev call Tc?

21.  What is NH3? Provide its common name and IUPAC name.

  1. What phase is NH3?
  2. Write a Bronsted-Lowry reaction of NH3 in water.
  3. What is the arrangement of the NH3? What is the shape?
  4. Sketch the following for NH3.
  5. Structural formula
  6. Space filling model
  7. Ball and stick model
  8. Show how NH3 can be categorized as a Lewis base by drawing it Lewis dot structure, complete with partial positive and partial negative ends, overall dipole and sketched with the proper bond angle.

22.  The formulas and common names for several substances are given below. Give the systematic names for these substances.

  1. Sugar of lead Pb(C2H3O2)2
  2. Blue vitrol CuSO4
  3. Quicklime CaO
  4. Epsom salts MgSO4 ∙ 7 H2O
  5. Milk of magnesia Mg(OH)2
  6. Gypsum CaSO4
  7. Laughing gas N2O
  8. Muriatic acid HCl

23.  Identify each of the following elements:

  1. A member of the same family as oxygen whose most stable ion contains 54 electrons.
  2. A member of the alkali metal family whose most stable ion contains 36 electrons.
  3. A noble gas with 18 protons in the nucleus
  4. A halogen with 85 protons and 85 electrons

24.  Show that the following data are consistent with the law of multiple proportions.

Mass of carbon in a 1 g sample / Mass of hydrogen in a 1 gram sample
Methane / 0.749 g / 0.251 g
Ethane / 0.799 g / 0.201 g
Propane / 0.817 g / 0.183 g

25.  In the following 2x2 crossword, each letter must be correct four ways.

1 / 2
3 / 4

Horizontal

1-2: two letter symbol for a metal used in ancient times

3-4: two letter symbol for a metal that burns in air and is found in group VI

Vertical

1-3: two letter symbol for a metalloid

2-4: two letter symbol for a metal used in US coins

Single squares

1: a colorful non-metal

2: a colorless gaseous nonmetal

3: an element that makes fireworks green

4: an element that has medicinal uses

Diagonal

1-4: two letter symbol for an element used in electronics

2-3: two letter symbol for a metal used with Zr to make wires from superconducting magnets

26.  Tums is a popular remedy for acid indigestion. A typical Tums tablet contains calcium carbonate plus some inert substances. When ingested, it reacts with the gastric juice (hydrochloric acid) in the stomach to give off carbon dioxide gas. When a 1.328 gram tablet reacted with 40.00 ml of hydrochloric acid (density 1.140 g/ ml), carbon dioxide gas was given off and the resulting solution weighed 46.699 g. Calculate the number of liters of carbon dioxide gas released if its density is 1.81 g/ L.

27.  Which of the following are elements, which are molecules but not compounds, which are compounds but not molecules, and which are both compounds and molecules, which are allotropes?

  1. SO2
  2. S8
  3. Cs
  4. N2O5
  5. O3
  6. O2
  7. CH4
  8. CH4
  9. KBr
  10. S
  11. P4
  12. LiF
  13. CaCO3

28.  Write the molecular and empirical formula for the following compounds. Identify the substances.

Sketch the structural formula for each compound.

What does the dashed line within the ring represent in the structures above?

29.  In the Rutherford gold foil experiment, an α particle was shot directly toward a gold nucleus. The particle will come to a halt when its kinetic energy is completely converted to electrical potential energy. When this happens, how close will the α particle with a kinetic energy of 6.0 x 10-14 Joules be from the nucleus? According to Coulomb’s law, the electrical potential energy between tow charged particles is E = kQ1Q2 / r where Q1 and Q2 are the charges (in Coulombs) of the α particle and the gold nucleus, r is the distance of separation in meters, and k is a constant equal to 9.0 x 109 kgm3/ s2C2. J is the unit of energy where 1 J = 1 kgm/s2.

30.  Write the nuclide symbol for an alpha particle.