The Periodic Law



The Periodic Law

The present organization of the elements is a product of the first periodic table published by Dmitri Mendeleev in 1869. The amazing accuracy of his predictions has been very important to chemists in this century. However, the basis of his arrangement was the atomic masses of the elements. This approach proved incorrect as it would have placed some elements in a family with dissimilar properties. Henry Moseley rearranged the table on the basis of the atomic numbers of the elements. In accordance with Moseley’s revision, the periodic law states: the properties of the elements are periodic functions of their atomic numbers.

Each of the 118 known elements has its own set of characteristic properties. These range from solid to gas, lustrous to dull, low to high melting points, various colors, and so on. The elements are arranged within the periodic table into groups or families (vertical columns) and periods or rows (horizontal rows). This arrangement reflects the periodic or repeating nature of the properties of the elements.

In this experiment, you will use your knowledge of periodic properties and a list of clues to correctly arrange the elements from a scrambled periodic table. You will also predict values for any information missing from the table.

Procedure:

The following sets of elements belong together in groups:

VWX, ALK, GJM, HYN,

PBST, ZIDR, CEF, OQU

Use the clues below to put the elements in order in groups 1,2,13,14,15,16,17,and 18.

P has an atomic number three times that of C

Q has a total of six electrons

D2M is the simple formula of an oxide

R is less dense than Z

Z is an alkali metal

S is a noble gas

Y is a liquid

A has the smallest atomic mass in its group

T has ten protons

H has an atomic number larger than N

L has the largest atomic mass in its group

W has 5 electrons in its outer energy level

I is a gas

B has an atomic number one higher than I

F is an alkaline earth metal with a mass number of 40

V is a metalloid

H is a halogen

The atomic mass of C is more than that of E

G has an atomic mass two times that of M

Atoms of D are larger than those of Z

X has an atomic number one less than M

The electrons of atom U are distributed over three energy levels

The atomic radius of J is the largest in the group

Fill the letters in the blanks on the periodic table given, and then fill out the information for each element on the back of that page. You must fill in the spaces for atomic number, symbol, oxidation number and phase (state of matter).

Answer the following questions.

1. Examine the completed periodic table. What general observations can be made of trends within rows and groups for the following properties?

a. density

b. mass

c. atomic radii

2. Where are the heavy metals located? Give three examples.

3. List four physical properties that distinguish metals from nonmetals.

4. List at least three reasons for the location of sodium on the periodic table.

5. Why do you think the transition metals were left out of this experiment?

6. What contribution did Henry Moseley make to the periodic table to make it “more perfect”?

7. When placing elements in the bottom two periods, why do you think oxidation numbers were used?

................
................

In order to avoid copyright disputes, this page is only a partial summary.

Google Online Preview   Download