CHEM 105 Chemical Periodicity PDF

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Virtual Chemical Periodicity Name: Kenzie Hutchins Introduction: In the 1860s about 60 elements were known. From their physical properties, the elements were classified as metals, nonmetals, or metalloids. Chemists of the time further classified the elements into groups. The elements in a particular group have similar chemical and/or physical properties. This classification led to the discovery of the periodic table and the periodic law. In the periodic table, elements are assigned to a period and a group—groups are the columns and the periods are the rows of the table. The periodic law states that the properties of the chemical elements vary with the atomic number in a systematic way. We now understand that the properties depend on the electronic structures of the atoms. Periodic Trend: Organization by Physical Properties Elements are organized in the periodic table in different groups. The first column are the alkali metals, the second column are the alkaline earth metals, and the middle of the table contains the transition metals. For this experiment, first write down the symbol for each element in the table. Then open the virtual chem lab and go into the inorganic module. Double click on the test tubes to get one. Then, choose the following ions to see them in solution. Write down what color you see and put an X in the category (alkali metals, alkaline earth metals, transition metals, or other) to which the ion belongs.

SUBSTANCE SODIUM POTASSIUM COBALT COPPER CHROMIUM MAGNESIUM CALCIUM NICKEL

SYMBOL NA K CO CU CR MG CA NI

SOLUTION COLOR CLEAR CLEAR RED BLUE PURPLE CLEAR CLEAR GREEN

ALKALI X X

ALKALINE EARTH

TRANSITION

X X X X X

Periodic Trends: Atomic Radius and Electronegativity For this section of the lab you will need to be able to draw directly in this file or you will need to print out the following image or recreate it on a sheet of paper. You will also require a ruler or some similar measuring device that will provide consistency even if it isn’t accurate. The image is an abbreviated version of the periodic table. Though it is missing several pieces, the overall trends would show if we used the whole table. This is to save you some time and effort while still being able to see the trend. You must show your work for full credit. This can be done by including the image with your worksheet file.

Virtual Chemical Periodicity

Use the following data tables to discover trends with atomic radius and electronegativity. Atomic radius is the distance from the nucleus of an atom to the outermost electron orbital. Electronegativity is the tendency of an atom to attract a shared pair of electrons toward itself. Use the data table for atomic radius to draw a circle in each box with the scale of 1 Angstrom = ½ cm. For example, if H has an atomic radius of 0.37 Angstroms, you would draw a circle with a radius of 0.185 cm. Use the data table for electronegativity to draw a vertical bar in each box with a scale of 1 Pauling = ½ cm. For example, if H has an electronegativity of 2.1 Paulings, you would draw a line with a length of 1.05 cm. Atomic Radius

1

2

3

5

8

10

11

13

16

18

Virtual Chemical Periodicity H

He

Li

B

O

Ne

Na

Al

S

Ar

0.37

0.31

1.52

0.85

0.73

0.71

1.86

1.43

1.03

0.98

5 B 2.0

8 O 3.5

10 Ne --

11 Na 0.9

13 Al 1.5

16 S 2.5

18 Ar --

Electronegativity

1 H 2.1

2 He --

3 Li 1.0

Questions: 1. Summarize the three trends you observed (solution color, atomic radius, and electronegativity). After this experiment I noticed that both Alkali Metals in the table and the Alkali Earth Metals were clear with no color, but the transition metals showed different colors. For the atomic radius the trend I noticed is that as it went down a group the radius got bigger, and when it goes across a period the radius got smaller. For electronegativity the trend was as it went down a group the electronegativity got smaller and across a period is got bigger.

2. Effective nuclear charge (Zeff) increases across a period. How does this affect atomic radius? Include shielding in your answer. If you want a refresher on these concepts check out this link. https://tinyurl.com/yad5ejl6

Because of an increase in electrons being added to the atoms the atomic radius decreases. There are more electrons to shield from the pull of the nucleus which makes the atom smaller.

3. A solution of Vanadium is green. Is it most likely to be an alkali metal, an alkaline earth metal, or a transition metal? It would be a transition metal

4. Why do you think there are no electronegativity values for the noble gases?

Because noble gases don’t want to gain or lose any electrons which would make it 0, this is because noble gases are the most stable...