1. Why is the Table of Elements Periodic?

2. On What Basis Did Mendeleev Arrange the Elements?

3. Mendeleev’s Table
Mendeleev arranged the elements by atomic mass (weight) and other physical and chemical properties
These properties repeated themselves periodically

4. Periodic Properties of Elements

5. Properties of Elements: Table S

6. Atomic Radius
Atomic radius – the distance from the nucleus to the outermost electrons, measured in picometers (10-12 m)

7. Ionization Energy
Ionization Energy - the energy needed to remove the outermost electron
Elements have multiple ionization energies: 1st, 2nd, 3rd, etc.

8. Lab 9: Periodic Properties of Groups of Elements
Objective
To examine the periodic properties of elements in groups (columns) of the periodic table.
Materials
Chemistry Reference Tables, graph paper, rulers, colored pencils.

9. Table S

10. Procedure
Using the blank partial periodic table provided, write the symbol of the element, the sublevel ground state electron configuration, the atomic radius of the element, and the first ionization energy of the element for the following:
Group 1: the alkali metals (except hydrogen)
Group 2: the alkali earths
Group 17: the halogens
Group 18: the noble gases (except helium)

11. Li 3
2-1
Radius
______pm
IE ________kJ

12. The atomic radius and first ionization energy data can be found on Table S.
Complete the table and follow the directions below for making two graphs: one for atomic radius of the four groups, the other for 1st ionization energy.

13. Making Graphs
You will be making two multiple line graphs that each contain four sets of data (four lines). Each group should be treated as a separate line; the line must be drawn in a different color.
Plot the atomic number, from 1-90, on the x axis. On the y axis, plot the atomic radius, in picometers. Make a suitable scale for each axis so that each data point can fit on the graph.
Be sure to indicate which group is which on your graph. You can use a legend for this, or you can label the individual lines.
The graph must have a descriptive title.

14. Ionization Energy Graph
For your second graph, plot 1st ionization energy (in kJ) on the y axis. The x axis should be similar to the first graph. This graph should be completed as homework for the next day if not finished in class.

15. Questions (answer in complete sentences, on a separate sheet of paper)
What happens to the atomic radius as you go down a group? Give a reasonable explanation for this trend.
What happens to the ionization energy as you go down each group? Account for this phenomenon.

16. Using electron configuration, explain why elements within groups have similar physical and chemical properties.
Define the following terms:
a) dependent variable b) independent variable
For each graph, identify which axis is the dependent and independent variable, respectively.

17. Lab 6: Periodic Properties Within Energy Levels of the Periodic Table
Objective: to examine the periodic properties of elements in periods 2 and 3 of the periodic table.
Same materials as lab 5.

18. Methods Using the blank partial periodic table provided, write
the symbol of the element
ground state electron configuration
the atomic radius of the element
first ionization energy of the element for periods 2, 3, and the first two elements of period 4.
Some of the data will be repeated from your previous assignment; copy that data onto this sheet.

19. Fill in Groups 1,2,17,18 from previous lab data table! 2 3 4 20 Ca
Radius ________pm
IE __________kJ

20. Making Graphs On the x axis, plot the atomic number, from 3-20.
On the y axis, plot the atomic radius, using a suitable scale. Units should be included.
Plot your points, putting an appropriate title on the graph. On your graph, you can identify the two periods and/or identify each element at every point if you wish.
Repeat the same process for ionization energy. The assignment must be completed by the following class as homework.

21. Questions (answer in complete sentences, on a separate sheet of paper)
What happens to the atomic radius as the atomic number increases across a period? Give a reasonable explanation for this trend.
In general, what happens to the ionization energy as the atomic number increases across a period? Explain your answer.
Compare ionization energies for the metallic elements to the non-metals. Why are they so different?
Identify the dependent and independent variables for each graph.

22. Extra credit
Filled sublevels and half filled sublevels have extra stability.
Elements that do not have these configurations have electrons in somewhat higher energy states and are easier to ionize.
Using this information and your knowledge of electron configurations, explain why there are two little “dips” in the 1st ionization energy as you move across each period.

24. Metals, Metalloids, Non-Metals

26. Atomic Radius increases down groups Atomic Radius decreases across periods

29. Atomic Radius increases down groups
Why?
More energy levels with larger elements
Higher energy levels, further from the nucleus, are filled with electrons

30. Atomic Radius decreases across periods
The nuclear charge is increasing across the period
The number of “blocking” electrons does not change – the blockers are in the lower energy levels
Electrons in the highest energy level don’t shield each other from the nucleus
The charge on consecutive elements becomes more effective, drawing the electrons closer to the nucleus.

31. Shielding Effect
Na outer electron is “blocked” more effectively than Cl electrons

33. Ionization Energy Decreases down groups
Generally increases across the table

34. Questions (answer in complete sentences, on a separate sheet of paper)
1. What happens to the atomic radius as the atomic number increases across a period? Give a reasonable explanation for this trend.
2. In general, what happens to the ionization energy as the atomic number increases across a period? Explain your answer.
3. Compare ionization energies for the metallic elements to the non-metals. Why are they so different?
4. Identify the dependent and independent variables for each graph.

36. Periodic Trends for Ionization Energy
For elements of the same group, ionization energy decreases due to shielding by more and more energy levels filled with electrons.
The valence electrons, being at higher energy than their cousins in lower periods, require less energy to leave the atom.

37. Ionization Energy Across Periods
Ionization generally increases across periods, because the effective nuclear charge is increasing with each added proton.
There a few exceptions due to interactions between electrons in groups 13 and 16.

38. Why the zig zags?

39. Ionic Radius

40. Ionic Radius: Metals
Metals tend to have large atomic radii, and small ionic radii
When metals lose electrons, they now have more protons than electrons, and the remaining e- are pulled closer to the nucleus
+ e-
Na atom: 11 p+, 11e-
Na+ ion: 11p+, 10 e- (noble gas configuration)

41. Ionic Radius: Non-Metals
Non-metals tend to have small atomic radii, and large ionic radii
When non-metals gain electrons, their increased repulsion enlarges the atom, and the nuclear charge is less able to keep the electrons close
+ e-
Cl atom: 17p+, 17 e-
Cl- ion: 17p+, 18e- (noble gas configuration)

42. Atomic and Ionic Radii Questions
Which is larger, Na or Na+ ?
Which is larger, Cl or Cl-?
Which is larger, Li or F?
Which is larger, K or Rb?
Which is larger, F or Br?
Which is larger, Na+ or K+ ?
Which is larger, I- or Br- ?