Reading Quiz1. How did Mendeleev organize his

periodic table?

2. How is the modern periodic table organized?

3. What are the three broad classes of elements?

4. What information is displayed on the periodic table for each element?

The History of the Modern

Periodic Table

During the nineteenth century, chemists began to categorize the elements according to similarities

in their physical and chemical properties. The end result of these studies was our modern

periodic table.

Johann Dobereiner

1780 - 1849

Model of triads

In 1829, he classified some elements into groups of three, which he called triads.The elements in a triad had similar chemical properties and orderly physical properties.

(ex. Cl, Br, I andCa, Sr, Ba)

John Newlands

1838 - 1898

Law of Octaves

In 1863, he suggested that elements be arranged in “octaves” because he noticed (after arranging the elements in order of increasing atomic mass) that certain properties repeated every 8th element.

John Newlands

1838 - 1898 Law of Octaves

Newlands' claim to see a repeating pattern was met with savage ridicule on its announcement. His classification of the elements, he was told, was as arbitrary as putting them in alphabetical order and his paper was rejected for publication by the Chemical Society.

John Newlands

1838 - 1898 Law of Octaves

His law of octaves failed beyond the element calcium. WHY?

Would his law of octaves work today with the first 20 elements?

Dmitri Mendeleev

1834 – 1907“Father of the

modern periodic table”

In 1869 he published a table of the elements organized by increasing atomic mass.

Lothar Meyer

1830 - 1895

At the same time, he published his own table of the elements organized by increasing atomic mass.

Elements known at this time

• Both Mendeleev and Meyer arranged the elements in order of increasing atomic mass.

• Both left vacant spaces where unknown elements should fit.

So why is Mendeleev called the “father of the modern periodic table” and not Meyer, or both?

• stated that if the atomic weight of an element caused it to be placed in the wrong group, then the weight must be wrong. (He corrected the atomic masses of Be, In, and U)

• was so confident in his table that he used it to predict the physical properties of three elements that were yet unknown.

Mendeleev...

After the discovery of these unknown elements between 1874 and 1885, and the fact that Mendeleev’s predictions for Sc, Ga, and Ge were amazingly close to the actual values, his table was generally accepted.

Prediction of Germanium’s Properties

Property Mendeleev’s Prediction Observed Properties

Atomic Weight 72 72.59

Density 5.5 5.35

Specific Heat 0.305 0.309

Melting point High 947 C

Color Dark gray Grayish white

Formula of oxide XO2 GeO2

Density of oxide 4.7 4.70

Formula of Chloride XCl4 GeCl4

Boiling point of chloride A little under 100 84 C

However, in spite of Mendeleev’s great achievement, problems arose when new elements were discovered and more accurate atomic weights determined. By looking at our modern periodic table, can you identify what problems might have caused chemists a headache?

Ar and KCo and NiTe and I

Th and Pa

Henry Moseley

1887 - 1915

In 1913, through his work with X-rays, he determined the actual nuclear charge (atomic number) of the elements*. He rearranged the elements in order of increasing atomic number.*“There is in the atom a fundamental quantity which increases by regular steps as we pass from each element to the next. This quantity can only be the charge on the central positive nucleus.”

Henry Moseley

His research was halted when the Britishgovernment sent him to serve as a footsoldier in WWI. He was killed in thefighting in Gallipoli by a sniper’s bullet, atthe age of 28. Because of this loss, theBritish government later restricted itsscientists to noncombatant duties duringWWII.

Glenn T. SeaborgAfter co-discovering 10 new elements, in 1944 he moved 14 elements out of the main body of the periodic table to their current location below the Lanthanide series. These became knownas the Actinide series.

1912 - 1999

Glenn T. SeaborgHe is the only person to have an element named after him while still alive.

1912 - 1999

"This is the greatest honor ever bestowed upon me - even better, I think, thanwinning the Nobel Prize."

Periodic Table Geography

The horizontal rows of the periodic table are called PERIODS.

The vertical columns of the periodic table are called GROUPS, or FAMILIES.

The elements in any groupof the periodic table havesimilar physical and chemicalproperties!

Periodic LawWhen elements are arranged in order of increasing atomic number, there is a periodic pattern in their physical and chemical properties.

Three broad classes of elements

1. Metals

*80 percent of the elements are metals

*good conductors of electricity

*high luster

*all solids at room temperature

-except Mercury

*ductile-can be drawn into wires

*malleable-hammered into thin sheets without breaking

Alkali Metals

Alkaline Earth Metals

Transition Metals

InnerTransition Metals

These elements are also called the rare-earth

elements.

Answer the following questions:1. What period is gold in?

2. What family/group is copper in ?(The name and #)

3. What period is barium in?

4. What family/group is cesium in?(The name and #)

5. Where are the inner transition metals on the periodic table? What are the inner transition metals also known as?

6. Who is considered the father of the modern periodic table?

7. What are three general properties of metals?

8. How is the current periodic table arranged? Who is responsible for this arrangement?

2. Nonmetals

*great variation in physical properties-opposite of metals

*poor conductors of heat and electricity* most gases at room temperature

* some solids (sulfur and phosphorus)-tend to brittle-shatter if hit with a hammer

* ones a liquid (bromine)*most located in the upper-right corner of the periodic table

-except for hydrogen

Halogens

Noble Gases

3. Metalloids*have properties that are similar to both metals and nonmetals

*properties depend on the condition

*silicon

*elements that border the stair-step line

-B, Si, Ge, As, Sb, Te, and Po

Electron Configuration in Groups

Write the electron configuration for:

Ne

Ar

Kr

Li

Na

K

The s and p block elementsare called

REPRESENTATIVE ELEMENTS.

Short cut for writing electron configurations

Ba: [Xe]6s2

W: [Xe]6s24f14 5d4

Ra

Pt

1. Identify each element as an alkali metal, an alkaline earth

metal, a halogen, a noble gas, transition metal, or inner

transition metal:

a. barium b. lithium c. chlorine d. beryllium

e. platinum f. uranium g. radon h. iodine

2. Into what four classes can elements be sorted into based on

their electron configurations?

3. Identify each element as a metal, a metalloid, or a nonmetal.

a. gold b. sulfur c. silicon d. barium

4. Which of the following sets of elements have similar physical

and chemical properties? Why?

a. oxygen, nitrogen, carbon, boron

b. strontium, magnesium, calcium, beryllium

c. nitrogen, neon, nickel, niobium

5. Name two elements that have properties similar to those of the

element sodium.

The periodic table is the most important tool in the chemist’s toolbox!

Test corrections:

Have until the end of class

Can use your notes and book

Free response

-on a separate sheet of paper (staple to original

test)

-correct any that you got wrong

-can earn up to ½ the points you got wrong back

-must show all work

M/C (Need to fill in the rescore bubble on top)

-earn up to 8 points back on M/C score

-Retest use questions 81-96 on your original

scan-tron

How was Mendeleev’s periodic table organized?How is the current periodic table organized?