Ch 19 Properties of Atomsand Periodic Table

Section 3 The Periodic Table

Essential Question

– How did Mendeleyev organize the elements?

ChemCatalyst •In 1889 a Russian chemistry teacher created an organized table of the elements. At the time only 63 different elements were known. Below is a reproduction of that table.

– What do you think the numbers represent?

(cont.)

You will be able to:

– Explain how the periodic table of elements is organized.

– Dimitri Mendeleyev is credited with organizing the elements into the first periodic table.

– The main properties that Mendeleyev used to sort the elements were reactivity with one another and a number describing the atomic weight of each element, vertically.

Notes

Activity

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

What to do?Arrange the cards you have been given according to the modern periodic table.

“Spokes” represent number of bonds an element will form

Completed Table(cont.)

Questions to Answer(Turn in for credit)

1. List three patterns that appear in your arrangement of this periodic table. (Be very detailed! If it helps, draw and label the drawing.)

A. _______________________________B. _______________________________C. _______________________________

2. Explain the placement of H and He. (Hint: Use the information and picture on the cards.)

3. What is missing from this periodic table, besides the one element under silicon?

Wait to turn this after completing the “Check-In”

Making Sense

•Below are five possible cards for the element germanium. Where does germanium belong in the table? Which card seems most accurate to you? What is your reasoning?

(cont.)

Germanium

Ge62.7

Germanium

Ge62.7

Germanium

Ge66.0

Germanium

Ge72.6

A B C

D E

Germanium

Ge72.6

(cont.)

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

Germanium

Ge

(cont.)

Check-In– Which of the following elements would

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

CadmiumCd

Moderately soft, silvery solid, metal

React very slowly with water

Found inCdCl2 (s)

ZincZn

Moderately hard, silvery solid, metal

Reacts very slowly with water

Found in ZnCl2 (s)

IodineI

Purple solid, nonmetal

Reacts slowly with metals

Found inICl (s)

MercuryHg

Silvery liquid, metal

Does not react with water

Found inHgCl2 (s)

Compare Periodic Tables

Mendeleyev Today (Moseley)

Both

1. Fold Hotdog, leaving holes out2. Fold in thirds

3. Draw interlocking ovals4. Label as shown below

5. Cut6. Complete information inside

Wrap-Up: Past and PresentPast: Mendeleyev Ted Ed• Late 1800’s, Russian chemistry teacher• Organized periodic table based on properties of

the elements, atomic mass vertically, repeating patterns

• Helped to predict the existence of undiscovered elements

Present: Moseley• 1913, young English scientist• Organized periodic table according to increasing

atomic number horizontally, predicts properties of unknown elements, repeating patterns

Ch 19 Section 3Electron Cloud Structure

Life on the Edge

The Big Question– What accounts for the similar chemistry

of elements in the same group(column)?

ChemCatalyst •The three atoms below have similar reactivity and chemical behavior.

– Where are these elements located on the periodic table?

– What do you think might be responsible for their similar properties?

(cont.)

(cont.)

You will be able to:

– Give the number of valence electrons for an element.

Activity

•Purpose: The various physical and chemical properties of the elements can be traced to the electrons. By studying electrons further we may be able to unlock the key to creating substances similar to gold. This lesson will reveal the arrangement of electrons within atoms.

Making Sense

– Explain how you can determine the arrangement of an element’s electrons, from the element’s position on the periodic table.

– Bohr proposed that electrons could be found in different shells around the nucleus.

– The letter “n” is referred to as the quantum number.

Notes

(cont.)

(cont.)

– The outermost shell of each drawing is called the valence shell.

– The valence shell contains the valence electrons.

– All other electrons are considered core electrons.

(cont.)

Work together on activity

Unit 1 • Investigation II

Notes

Check-In•Provide the following for element # 34a) The element’s name and symbol.b) The number of protons in the nucleus.c) The total number of electrons for this element.d) The number of core electrons for this element.e) The number of valence electrons.f) The group number for this element.g) The names of other elements with similar chemistry.

(cont.)

Wrap-Up– Electrons occupy different shells

around the nucleus of an atom.– Each electron shell can hold a specific

maximum number of electrons.– The valence electrons are in the

outermost electron shell of an atom. – Electrons that are not valence

electrons are called core electrons.

(cont.)

– Elements with the same number of valence electrons have similar chemistry and are in the same group.