ACTIVITIES: TRENDS IN THE PERIODIC TABLE

The activities in this section introduces students to trends found in the periodic table. It incorporates the theory of multiple intelligences and it can be a curricular framework for this unit. The following activities can be covered in three 50 minute periods and are designed to reach students with different learning styles.


ACTIVITY 1
Begin by reviewing the definitions of atom and ion by giving a sign to a student that reads "atom." Then reiterate the definition of the atom. The student then puts on a mask (or hat) of any type, and then give the student a sign that reads "ion." Explain to the class that this is still Mr./Ms. Atom, but he/she has on a disguise. His/her inside or nucleus is the same (i.e. number of protons), but the electron cloud has now changed. The student has lost or gained an electron, making them look different on the outside.


ACTIVITY 2
Each student is given a ping pong ball, which represents an electron. The students’ bodies represent the nucleus. Instruct the student to illustrate by moving their arms where the electron is most likely to be found. Students usually begin moving the ping pong ball around their bodies in a circular, orbital fashion. Next, select three students of different heights, and ask the class which one has the greatest atomic radius (have the students hold out their arms perpendicular to their body). Explain that two arm lengths equal a diameter and one arm length equals a radius. Have the rest of the students help arrange the three students in order of decreasing arm length or atomic size, pointing out how the arrangement is similar to the size trend reading across a period on the periodic table. Finally, rearrange the three students from shortest to tallest in a column format and discuss how this arrangement is similar to the atomic size trend reading down a group or family.


ACTIVITY 3
After explaining the relationship between shielding and atomic size, students demonstrate their understanding through bodily kinesthetic modeling. First number 18 students 1 through 18. Each number represents an element on the periodic table. Remind the students of the mnemonic "APE" (atomic number = number of protons = number of electrons).
To begin building the atom, put a student without a number in the center of the demonstration to represent the nucleus. Beginning with student 1, the students, representing electrons, add into the electron cloud at each energy level until student 18 is added. They should begin to see the periodic trend as they go across a period; electrons add to the same principal energy level simultaneously as protons add to the nucleus. Because no shielding is occurring, the pull of the positive nucleus is greater, making the atom smaller. Therefore, the smaller atoms are the last element of each period (excluding the noble gases). In contrast, the atomic size increases down a group due to the shielding effect.
Begin the demonstration again, this time giving numbers 1 through 19. Students 1, 3, 11, and 19 carry posters brightly marked with red numbers to illustrate group 1. Remind the students to concentrate on looking at the four students with red numbers. Beginning with student 1, students join the electron cloud until student 19 is added. Students should realize that the red coloured students add to different energy levels: Lithium, element 3, has one energy level shield; sodium element 11, has two energy level shields; and potassium, element 19, has three energy level shields. Even though additional protons are being added to the nucleus, increasing its positive charge, the attraction is counteracted by the shielding of the lower energy levels. Students realize that the atomic radius increases down a group on the periodic table because of the shielding effect of lower energy levels.


ACTIVITY 4
After explaining the relationship between atomic size and ionization energy, demonstrate it by using a basketball. Ask the students where should you hold the ball to prevent an opposing player from stealing it. Most students would reply "close to the body." Explain to the students that the same relationship exists with atoms- it is easier to snatch an electron away from a larger atom than from a smaller atom.
Tell the students to imagine that the ball is an electron. Ask them how much energy will the opponent have to exert to snatch away the ball (electron) if you hold it far away (as in a large atom) from the body versus close to the body (as in a small atom)? Summarize the demonstration by stating the inverse relationship between ionization energy and atomic size.


ACTIVITY 5
Immediately after activity 4, choose a volunteer from the class to put on an apron and goggles. Instruct the student to pretend he/she is an atom. Hand the student a ping pong ball and tell the class it is an electron. The student is a big atom and is holding the ball in his/her hand away from his/her body. Take a hair dryer, representing ionization energy, and blow the electron out of the student’s hand, transforming the student into an ion.
Repeat the demonstration but this time tell the student that he/she represents a small atom. The ball/electron is placed on the student’s head. Pull out a leaf blower and blast the electron with high ionization energy. Summarize the demonstration by explaining the inverse relationship between ionization energy and atomic size.


ACTIVITY 6
Have students produce various graphs using atomic numbers, atomic radii, and ionization energies of elements 1 through 20 with graphing calculators. Students who have difficulty with the calculators can reinforce these skills by sketching the graphs by hand using only the maxima and minima.