Alchemy Unit – Investigation II

Lesson 4: Create a Table

ChemCatalyst

In 1889 a Russian chemistry teacher, Dmitri Mendeleev, created an organized table of the elements. At the time only 63 different elements were known. On the next slide, you will see a reproduction of that table.

(cont.)

• What do you think the numbers represent?

The Big Question

• How did Mendeleyev organize the elements?

You will be able to:

• Explain how the periodic table of elements is organized.

Activity

Purpose: The goal of this lesson is to acquaint you with Mendeleev’s organization of the elements by allowing you to create your own table from the patterns you see in the elements.

Activity

• Examine the cards. Describe five different ways you can sort and organize the cards into groups.

• What are three ways you can arrange your 33 cards in order.

• Dimitri Mendeleev is credited with organizing the elements into the first periodic table.

• Mendeleev grouped the elements by reactivity and arranged the elements according to a number that describes the relative weight of each element called the atomic weight.

Activity

• One set of elements Mendeleyev grouped together was Magnesium, Calcium and Strontium.

Activity

Activity • One group of elements that Mendeleyev put into

the same group on the periodic table was magnesium, calcium and strontium. Copy the table and fill out the table below.

Element Description Reaction with air

Reaction with acid

Found in

Magnesium Mg

Found in MgCl2 (s)

Calcium Ca

Found in CaCl2 (s)

Strontium Sr

Found in SrCl2 (s)

• Magnesium reacting in air

Activity - magnesium

• Magnesium reacting in acids

Activity - magnesium

• Calcium reacting in air

Activity - calcium

• Calcium reacting in acids

Activity - calcium

• Strontium reacting in air

Activity - strontium

• Strontium reacting in acids

Activity - strontium

Activity

• Although you don’t have other metals to compare your observations with, the chemical behavior of these metals are unlike many other metals.

• Locate the cards of these three elements and then arrange the other 30 cards around them.

Activity

• Stack the cards in order of increasing atomic weight (the number on the card)

• What is the lightest element in your deck? The heaviest?

• Begin laying the cards out in a row until you get to magnesium. What element has similar properties to Magnesium?

Activity

• Mendeleev placed the elements with similar properties in the same column. Which column does magnesium fit the best?

• Pick up the card for sodium? What element card does it resemble? Place it under that card.

• Continue until you have all the cards laid out.

(cont.)

•  Notice there is a card missing in the middle.

• Notice where hydrogen and helium were placed. Why do you think they were placed in those columns?

• What information should be on this card?… (cont.)

•  How do you think Mendeleev knew there was a gap in the middle?

Germanium

Ge 62.7

Germanium

Ge 62.7

Germanium

Ge 66.0

Germanium

Ge 72.6

A B C

D

Germanium

Ge 72.6

(cont.) E

• Below are five possible cards for the missing element we call germanium. Which card seems most accurate to you? What is your reasoning?

• What would you add to the three empty corners to complete the card?

(cont.)

(cont.)

Germanium ? Moderately hard Silvery solid metalloid

? ?

Ge 72.6

Reacts very slowly With oxygen

Found in GeH4 gas

Check-In • Which of the following elements would

you find in the same group on the periodic table? Explain your thinking.

Cadmium Cd

Moderately soft, silvery solid, metal

React very slowly with water

Found in CdCl2 (s)

Zinc Zn

Moderately hard silvery solid, metal

Reacts very slowly with water

Found in ZnCl2 (s)

Iodine I

Bluish black solid, nonmetal

Reacts slowly with metals

Found in ICl (s)

Mercury Hg

Silvery liquid, metal

Does not react with water

Found in HgCl2 (s)

Wrap-Up

• Mendeleyev organized the periodic table based on the properties of the elements.

• Mendeleyev’s arrangement of the elements helped to predict the existence of undiscovered elements.