Download The Periodic Table

The Periodic Table
Chapter 6
Chemistry
 At the end of the 1700’s, only about 30
elements had been identified. Included in
this were the elements that had been
known since ancient times like Cu and Au.
 In less than 100 years the number of
elements had doubled, and scientists
needed a better way of classifying them.
Antoine Lavoisier
Late 1790s
Compiled a list of the 23 known
elements
In the 1800s the list exploded as
more and more elements were
discovered.
J. W. Dobereiner
 Early 1800’s
 Organized elements in groups of 3 called
triads.
 He based his triads on similarities in
properties between elements. 2 of his triads
were Li, Na, & K and Cl, Br, & I.
 Within the triads the middle elements often
had properties that were approximately the
average of the 1st & 3rd elements.
John Newlands
 1864
 Noticed when he arranged the elements
in order of increasing atomic mass, their
properties repeated every eight element.
 The
first & eighth elements had similar
properties
 Periodic: a pattern that repeats itself in a
specific manner
John Newlands
 Called his observations the “Law of Octaves”
 b/c
an octave in music is a group of notes that
repeats every eighth tone.
 Acceptance of this law did not last very long b/c
it didn’t work for ALL of the known elements.
 He was basically correct though – the
properties of elements do repeat in a periodic
way.
Dmitri Mendeleev & Lothar Meyer
 Demonstrated a connection between
atomic mass & elemental properties.
 Mendeleev is given more credit b/c he
published his organization scheme first &
demonstrated its usefulness.
Mendeleev’s Periodic Table
Dmitri Mendeleev
Mendeleev By Michael Offutt
He was born in Russia in 1834
Hard work as a youth opened up the college doors.
He always tried to be the best that he could be,
And chose to make his mark in Chemistry.
Chorus: Who told the elements where to go?
Mendeleev!
Who put them in columns and in rows?
Mendeleev!
Who was ready, who was able to make a
periodic table,
Who was that chemist? Mendeleev!
He wondered if nature really had a master plan
If the elements had a pattern that one could understand,
So he bought a bunch of cards and on each one wrote
the name,
Of an element and its weight, and then he played the
game.
He put them all in order by their atomic weights,
Used their chemical properties to differentiate.
Groups began to form and despite some question
marks,
He managed to produce a simple periodic chart.
Chorus
At first in 1869 the chart was not a hit,
But that young Russian chemist was not the kind
to quit.
He revised atomic weights and staked his whole
career,
Predicting that several new elements would
appear.
A few years passed and sure enough they came,
Gallium, scandium, germanium were their names.
Chemists everywhere were impressed with what
they saw.
There really must be something to this periodic
law.
So they call him the father of the periodic table,
And his work gave rise to another kind of label.
It’s the name for elements number 101,
In honor of this man they call it Mendelevium.
Chorus
Dmitri Mendeleev
 Russian Chemist
 Placed element’s atomic mass and
properties on cards
 Arranged elements looking for trends
 When arranged in order of increasing
atomic mass, similar properties appeared
at regular intervals.
Dmitri Mendeleev
 Created a table published in 1869
 Several empty spaces in his table.
 In 1871, he boldly predicted the
existence of several elements.
 By 1886 all three were discovered!
 The success of his predictions led to the
acceptance of his periodic table.
Dmitri Mendeleev
 His periodic table is NOT entirely correct.
 Several
order.
elements were not in correct
Henry Moseley
 1911
 Discovered why a few elements could not
be arranged according to their atomic
masses.
 Led to the current arrangement of the
current Periodic Table by atomic number.
 This
arrangement allowed a clear pattern of
periodic patterns.
 Still used today!
The Modern Periodic Table
 Groups:
columns on
the periodic
table. Also
referred to as
families
 Periods:
rows on the
periodic table
Janet Periodic Table
Modern Russian Table
Chinese Periodic Table
Stowe Periodic Table
Benfey Spiral Periodic Table
Triangular Periodic Table
“Mayan” Periodic Table
 The Mayan Periodic Table
of Elements, named for its
similarity to an ancient
calendar, is based on
electron shells.
 The shells are shown as
concentric circles and the
elements with completed
shells are arranged
vertically from the center
to the top of the circle.
Giguere Periodic Table
Play the Element Song
http://privatehand.com/flash/elements.html
Three Major Groups of Elements
 1. Metals: shiny, smooth, good
conductors. Solid at room temperature.
Most are malleable & ductile.
 2. Nonmetals: gasses or brittle solids,
poor conductors, only liquid is bromine
 3. Metalloids: elements with properties of
metals and nonmetals. (Also called
semimetals)
The Periodic Law
 The properties of the elements are periodic
functions of their atomic numbers.
Main Families: Be able to identify.
 Alkali Metals: Group 1A
 Alkaline Earth Metals: Group 2A
 Transition Metals: Group B elements
 Inner Transition Metals: Lanthanides &
Actinides – bottom rows of the periodic table
 Halogens: Group 7A – highly reactive
 Noble Gases: Group 8A – extremely
nonreactive
 Elements in the same family have similar
properties because their outer electron
configurations are the same
Representative Elements
 These are the elements in the s & p-blocks
of the periodic table.
 They display the entire range of elemental
characteristics found on the periodic table.
Periodic Table with Group Names
Periodic Trends
 As you compare elements from left to right across the
periodic table, you will notice a trend or regular
change in a number of properties due to the periodic
law.
 Trends to learn:






Atomic radii
Ionic radii
Ionization energy
Electronegativity
Electron Affinity
Metallic Character
 Show the trends on your periodic table.
Atomic Radii
 Atomic radius –
one half the
distance between
the nuclei of two
atoms of a
molecule.
Atomic Radii
Decrease across the periods.
 Caused by the increasing positive charge
of the nucleus
Increase down the group ( A few
exceptions)
electron is in higher energy levels –
farther from the nucleus.
 Outer
Group trends
 As we go down a
group
 Each atom has
another energy
level,
 So the atoms get
bigger.
H
Li
Na
K
Rb
Ionic Radii
 Ion: an atom or a bonded group of atoms
that has a charge
 Cation – positive ion
 Loss
of electron; decrease in radius
 Due to loss of valence electrons, there might
be an empty orbital, and less repulsion
between electrons means they can be pulled
closer to the nucleus
Ionic Radii
 Anion – negative ion
 Gain of electron; increase in radius
 More electrons around the nucleus
means a greater repulsion between
electrons, so they spread out more
Ionic Radii
 Metals on the left form cations
 Nonmetals on the right form anions
 As you move to the right on the Periodic
Table, the size decreases.
 As you move down a column, the size
increases
Ionization Energy
Ionization energy – energy required to
remove an electron from a neutral
atom
Ionization Energy
 Across the periodic table the ionization energy
increases.

Caused by the increasing positive nuclear charge
which attracts electrons more strongly. This results
in more energy required to remove an electron.
 Down the Groups, the ionization energy
decreases.

Caused by the increased size of the atoms. The
electrons that are farther from the nucleus are
easier to remove.
Ionization Energy
Another Way to Look at Ionization Energy
Electronegativity
 Electronegativity – the relative ability of an
atom to attract electrons in a chemical bond
 Across the periodic table electronegativity
increases.
 Elements
on the right of the table tend to
gain electrons – have higher
electronegativities
 Down a group electronegativity decreases.
 Electrons are farther away from the nucleus
so there is less attraction to the nucleus
Electron Affinity
 Electron affinity is a measure of an atom′s
ability to gain an electron.
 It increases across a period because the
increasing positive nuclear charge attracts
electrons more strongly.
 Electron affinities generally become smaller
down a column of the periodic table. The
electron being added to the atom is placed
in larger orbitals, where it spends less time
near the nucleus of the atom.
Metallic Character
 The metallic character of an element can be defined
as how readily an atom can lose an electron.
 From right to left across a period, metallic character
increases because the attraction between valence
electron and the nucleus is weaker, enabling an easier
loss of electrons.
 Metallic character increases as you move down a
group because the atomic size is increasing.
 When the atomic size increases, the outer valence
shells are farther away. The electrons of the
valence shell have less attraction to the nucleus
and, as a result, can lose electrons more readily.