the periodic table history of the periodic table 1) doberiner - doberiner’s triads grouped...

The Periodic TableHistory of the Periodic Table

1) Doberiner - Doberiner’s triads• Grouped together elements in groups of 3’s with

similar chemical properties.(ex) Cl, Br, I

Ca, Ba, Sr• Discovered that the atomic mass of one element from the triad is close to the ave atomic mass of

the the other two elements from the triad.• Found 4-5 triads

• First attempt to classify the elements in any way.

2) John Newlands• First to lay things out horizontally by increasing at.

mass.• When the properties of a series (row) began to

repeat themselves he started a new row.• Noted that every 8th element was similar to the

first• Law of Octaves: That when the elements were

placed in order by increasing atomic mass every 8th element had similar properties to the 1st element.

• He obtained 7 groups of 7.

3) Sir William Ramsay - discovered the Noble (Inert) gases in the 1890’s.

4) Demitri Mendeleev (1869)• Consisted of rows & columns.

• Elements placed in order by increasing at. Mass• Left to right and top to bottom.

• Placed elements with similar properties in the same column.

• 8 columns wide.• Sometimes the elements properties did not line up

properly. As a result he believed that not all the elements had been discovered.

• Therefore, left gaps in his P. Table for the undiscovered elements.

• Predicted the chemical properties of these undiscovered elements and was very accurate in

doing so.• Mendeleev’s Periodic Law: Properties of

elements are a periodic function of their at. mass. (If you order the elements by increasing at. mass the properties of the elements go thru a cycle and

repeat themselves).

• Also discovered a problem with the P. Table. If he ordered the elements by increasing at. Mass

some of the properties of the elements were out of order. (ex) Co and Ni

• But if he lined the elements up by properties not all of the atomic masses were in order.

• Discovered the problem, but did not know what to do about it.

5) Mosely• 45 years later Mosely solved Mendeleev’s

problem with the properties not lining up when you ordered the elements by increasing at. mass.

• Mosely was performing x-ray experiments that showed the # of protons per nucleus varied

progressively from element to element.• X-rays are a form of electromagnetic radiation.• X-rays have high frequency and therefore short

wavelengths.• X-rays are produced when high speed electrons

hit a metal target in an evacuated tube.

• Mosely discovered that the higher the atomic # (Z) = #p, the shorter the wavelength of the x-ray.

• He found in some cases the wavelength was 2x shorter than he expected - proved Mendeleev correct in that some elements had not yet been discovered.• When he listed elements by increasing at. # (Z) instead of increasing at . mass the properties lined

up.• The Periodic Law - the properties of the elements

are a periodic function of their at. #.• When you list the elements by increasing at. # the properties of the elements go thru a cycle and repeat

themselves.

Arrangement of the Modern Periodic Table• Horizontal row = series or a period• Vertical column = Group or family.

Draw diagram on the board.Draw diagram on the board.• Elements with similar properties have the same

number of outer shell e- (valence e-) and are in the same Group on the P. Table.

•Name of elements on the P. Table.•Group IA = 1 valence e- = alkali metals

•Group IIA = 2 valence e- = alkaline earths

Group IIIA = 3 valence e- = B familyGroup IVA = 4 valence e- = C familyGroup VA = 5 valence e- = N familyGroup VIA = 6 valence e- = O family

• (Groups IIIA - VIA are named according to the top element in the family.)

Group VIIA = 7 valence e- = halogensGroup VIIIA = 8 valence e- = Nobel or Inert

gases (octet = stable)• No compounds containing He, Ne, and Ar are

known.

• A few compounds contain Kr, Xe, and Rn.• Transition Elements = d sect. of P. Table

• Transition elements and the bottom of the p sect. = heavy metals.

• 4f series = lanthanide series (La - Yb).• 5f series = actinide series (Ac - No).

• f sect. = rare earthsMetals, nonmetals, and metalloids

•Metals - left of the P. steps•Nonmetals - right of the P. steps.

•Metalloids - border the P. steps on 2 sides (except Al)

• Most active metal is left and bottom. Also the most basic.

• Most active nonmetal is right and top. Also the most acidic.

• Metals tend to have 3 or fewer valance e-.• Nonmetals tend to have 5 or more valence e-.

• Determining the Outer Most Electrons by Position on the Periodic Table

(ex) 51 SbSteps:

1) Locate sect. = sublevel2) count down = en level

3) count over = # of valence e-(ex) 46 Pd

(ex) 74 W

(ex) 95 Am

Locating the element from the last subshell to receive electrons

Steps:1) sect.

2) en level3) # valence e-

(ex) 4p4

(ex) 5d6

(ex) 5f4

Periodic Properties•An element’s position on the periodic table and its

properties are a result of e- configuration.•Atoms of elements in the same column have

similar outer e- configurations.•The change in structure from one column to the next as we scan the p. table varies in a set way.

•Properties can be predicted by e- configuration as well as the position on the P. table.

Trends in Properties 1) Types of ElementsA) Series

metals -- metalloids -- nonmetals -- Noble gases (border the steps)B) FamilyIA VA VIAMetals nonmetals nonmetals

metalloids metals metalloids

Summary nonmetals

metals -- metalloids -- nonmetals -- Noble gases metals

2) Atomic RadiusA) Family (draw graph)(draw graph)Atomic size increases as you go down a family.Show examples down a family.Show examples down a family.

• Generally as you go down a family, each element has one more shell or en level than the element

above it. An increase in the number of en levels means an increase in the distance from the nucleus

making the atoms larger.• Due to an increase in the number of en levels there is also an increase in the screening or shielding effect (when inner en levels block the nuclear pull on outer en level e-). Since the e- are not held as tightly the size of the atom increases.• Atoms are becoming more metallic and therefore want to lose e- and do not hold them as tightly making the atom larger.

•B) Series (draw graph)(draw graph)• Generally there is a decrease in size across a series. Each element has a greater (+) charge which results in a greater total force of attraction between the (+) nucleus and the (-) electrons.• There are more e- added also but no new en levels. The increase in p overcompensates for the increase in e-.• Atoms become more nonmetallic want to gain e- so hold onto their existing e- very tightly.• Becoming more stable so hold the e- they already have very tightly.

• Group VIIIA gets bigger, but not as big as Group IA.

• It is believed that Group VIIIA gets bigger due to the fact that it is stable.

•Summarize!Summarize!Radi of Ions

• Which is bigger a Na atom or an Na ion and give all reasons why? Explain on the board.Explain on the board.

• Which is bigger a Cl atom or a Cl ion and give all reasons why? Explain on the board.Explain on the board.

• Metallic atoms lose e- to from smaller ions.• Nonmetallic atoms gain e- to form larger ions.

3) First Ionization Energy (I.E.)• The amount of energy needed to remove 1 e-

from an atom.

Atom + en -----> cation + 1e-

• 1st I.E. - en needed to remove the 1st e-.• 2nd I.E. - en needed to remove the 2nd e-.• 3rd I.E. - en needed to remove the 3rd e-.

• Write the I.E. for Na (do this on the board)(do this on the board)A) Series (draw graph)(draw graph)How? I.B) Family (draw graph)(draw graph)

SummarySummary

Ionization energies to remove successive e- • I.E. for success e- increases because as you

move more e- there will be less e- than p resulting in a greater nuclear pull (the e- are held more

tightly) therefore, requiring more en to rip e- off.

(ex) write the 3 I.E’s for Al (put this on the (put this on the board)board)

4) Electron Affinity (E.A.)• An element’s desire for additional electrons.• The amount of en released when you add an

e-.

Atom + 1 e- ------> en + Anion

A) seriesHow?

E. A. increases as you go across a series.Why?

•The atoms are becoming more nonmetallic, therefore they want to gain e-.

•The atoms are becoming smaller - strong nuclear pull.

•The atoms are becoming closer to being stable and gaining e- will make them even closer.

B) FamilyHow?

E.A. decreases down a familyWhy?

• Atoms are becoming more metallic - want to lose e- not gain.

• Atoms are becoming bigger, decrease in nuclear pull - can’t hold their own e- very tightly so do not

want more.• More en levels therefore atoms are larger and have a larger screening/shielding effect which decreases the nuclear pull - own e- are not being held tightly -

do not want more.

5) ElectronegativityAn atom’s desire to share e-.

A) seriesHow?

Electronegativity increases across a series.Why?

The same reasons as for E.A.B) Family

Electronegativity decreases down a family.Why?

The same reasons as for E.A.

Summary of all Trends and Properties:SummarizeSummarize