Chapter 1 – Activity 7

How Atoms Interact With Each Other

What Do You See? – pg 58
What Do You Think?
·  How does the arrangement of electrons in an atom determine its chemical behavior?
·  How might the valence electrons of sodium and chlorine interact to create the bond in NaCl?

Investigate

Part A – Ionic Bonds

Atoms are in their most stable form when the outer orbitals (s and p) are filled with electrons. Some atoms lose or gain electrons to form ions that have charges. When ions form, they produce atoms with a more stable electron arrangement.

Element / Number of Electrons in Atom / Electron configuration of atom / Number of Valence Electrons / Charge on ion formed / Number of Electrons in Ion / Electron Configuration of Ion
Lithium / 1s22s1
Beryllium / 1s22s2
Boron / 1s22s22p1
Carbon / 1s22s22p2
Nitrogen / 1s22s22p3
Oxygen / 1s22s22p4
Fluorine / 1s22s22p5
Neon / 1s22s22p6

1) When ions form, their electron configurations become exactly like what group on the periodic table?

______

2) How many valence electrons do most elements on the periodic table want to have to be chemically stable? ______

3) What elements need only two valence electrons to become chemically stable? ______

4) Fill out the table below to show what happens to the number of protons, neutrons, and electrons when atoms form ions.

Ion / Charge on ion / Atomic
Number / Atomic Mass / Protons / Neutrons / Electrons
Ca2+ / +2 / 40
Na+ / +1 / 12
F- / -1 / 10
N3- / -3 / 14

4) What is an ionic bond?

______

______

______

______

5) Draw a picture to show how electrons are transferred from a lithium atom to a fluorine atom when the ionic compound LiF forms.


6. You have learned how to write the formulas of and name ionic compounds in previous lessons. Practice writing and naming the ionic compounds that form

Formula Name

a) Mg2+ and Cl- ______

b) Na+ and O2- ______

c) K+ and I- ______

d) Cu2+ and S2- ______

e) Al3+ and O2- ______

f) Ba2+ and Br- ______

g) Ca2+ and F- ______

h) Fe3+ and O2- ______

i) Ni2+ and Cl- ______

j) Be2+ and P3- ______


Part B – More Practice With Ionic Compounds

For each pair of ions listed, write the chemical formula and the name of the compound that would form.

Formula Name

1) Li+ and O2- ______

2) Mg2+ and N3- ______

3) Ca2+ and S2- ______

4) Cu2+ and O2- ______

5) Al3+ and I- ______

6) Na+ and P3- ______

7) Fe3+ and Br- ______

8) K+ and S2- ______

9) Zn2+ and Cl- ______

10) Cr3+ and O2- ______

11) K+ and Cl- ______

12) Ba2+ and I- ______

13) Sr2+ and O2- ______

14) Co2+ and N3- ______

15) Mg2+ and O2- ______


Part C – Ionic or Covalent?

Compounds can be classified by the types of bonds that hold their atoms together. Ions are held together by ionic bonds in ionic compounds; atoms are held together by covalent bonds in molecular compounds.

You cannot tell whether a substance is ionic or covalent just by looking at a sample of it because both types of compounds can look similar. However, simple tests can be done to classify compounds by type because each type has a set of characteristic properties shared by most members. Ionic compounds are usually hard, brittle, water-soluble, have high melting points and can conduct electricity when dissolved in water. Molecular compounds can be soft, hard, or flexible; are usually less water-soluble; have lower melting points and cannot conduct electricity when dissolved in water.

Problem:

How can you identify ionic and molecular compounds by their properties?

Materials:

Marking pencil

4 pieces of Aluminum foil

Hot plate

Spatula

4 x 100ml beakers

Glass stirrer

Balance

Conductivity tester

10ml graduated cylinder

1-2 gram samples of 4 solids

Procedure:

1.  Use the pencil to label the aluminum foil pieces A, B, C, and D.

2.  Use a spatula to place about 0.1-0.2 grams of each of the 4 solids in the correct aluminum piece. Be sure to clean the spatula for each sample.

3.  Place the foil on a hot plate. Turn the heat setting to 4 and begin to heat the aluminum foil dishes. Leave the dishes on the hot plate for up to 10 minutes. Remove the dishes after 10 minutes. DO NOT allow materials to burn. Observe each solid and record which substances have melted. Turn off the hot plate.

4.  Label four beakers A through D.

5.  Weigh out 1.0g of each of the four solids, and place the weighed samples in their labeled beakers.

6.  Add 10mL of distilled water to each beaker.

7.  Stir each substance, using a clean glass stirrer for each sample. Note in your data table whether or not the sample dissolved completely.

8.  Obtain a conductivity tester from your teacher. Record whether or not each substance acts as a conductor in your data table.

Substance

/ Did it melt? / Did it dissolve in water? / Did it conduct electricity? / Classification – Ionic or covalent?
A
B
C
D

Analyze and Conclude:

1.  What happened to the bonds between the molecules when a substance melted?

2.  Did all compounds melt at the same temperature?

3.  Using your data classify each substance you tested as ionic or molecular compounds.

Apply and Assess:

1.  What are the differences in properties between ionic and covalent compounds?

2.  How did the melting points of the ionic compounds and covalent compounds compare?

Part D – Covalent Compounds

Some atoms choose to fill their outer orbitals by sharing electrons.

1) What is a covalent bond?

______

______

______

______

2) State the octet rule.

______

______

3) Take notes as your teacher shows you how to draw a Lewis dot structure to show how atoms are shared in covalent compounds.

H2O

Draw Lewis dot structures for the following compounds.

4) I2 5) OF2

6) PCl3 7) SiO2

Part E – More Practice with Lewis Dot Structures

1) NH3 2) CH4

3) H2S 4) NF3

5) O2 6) NO2


7) CO2 8) SO2

9) CCl4 10) OCl2

11) N2 12) Cl2

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