the periodic chart from then to now... the history 1669-henning brand discovered phosphorus...
TRANSCRIPT
The Periodic Chart
From then to Now . . .
The History 1669-Henning Brand discovered Phosphorus 1680-Robert Boyle rediscovered Phosphorus 1789-Lavosier wrote the 1st chemistry text 1809-There were 47 known elements 1862-Beguyer deChancourtois noticed periodicity 1863-Newlands classified 56 elements into 11 groups, octaves 1869-Mendeleev created a table and was able to predict the
existence of 2 new elements 1869-Meyer also created a table, but did not get the credit for it 1900-Moseley developed the Periodic Law 1944-Seaborg proposed the Actinide series
History of the periodic table
In the 1700’s only 30 elements were identified
Dobereiner in the 1800’s noticed certain elements could be grouped into sets of 3 called triads
Dobereiner--triads
TRIAD PROPERTIES Properties similar – Group 1 are soft metals Reactiveness similar – Group 1 are very
reactive with water Middle element value is average of one
above and one below
Triad—3 elements with similar properties
one value is an average of the other 2
PROPERTIES OF TRIADS
Li (3)
Atomic number
Ca 40.1 amu
Atomic mass
Cl 1.56 g/cm3
Density
Na (11)
Atomic number
Sr 87.6 amu
Atomic mass
Br 3.12 g/cm3
Density
K (19)
Atomic Number
Ba 137.0 amu
Atomic mass
I 4.95 g/cm3
Density
Newlands – mid 1800’s
Now 49 elements Noticed that when arranged by
increasing mass, every 8th element had similar properties
Called law of octaves
Newlands -- octaves
MENDELEEV VS MEYER
Both made discoveries at the same time but Mendeleev was the first to publish them
Wrote names and properties on cards and arranged them in various ways:
In increasing massIn repetitive properties
Both couldn’t be done at the same time Decided putting them in order of repetitive
properties was more important
DISCREPANCIES
In order to put the elements in similar groups according to properties, some of the masses were out of order
Thought that the atomic masses were wrong
MENDELEEV’S PERIODIC TABLE
When he put elements in order according to their properties without regard to their masses, some elements seemed to be missing
He predicted the existence of these missing elements and when discovered, they fit perfectly into his pattern
But – Mendeleev was not entirely correct The atomic masses, when recalibrated, were not incorrect.
This left some atomic masses out of order on his periodic table
Mendeleev’s notes
Mendeleev’s 1869 Periodic Table
LATE 1800’S MOSELY’S PERIODIC TABLE Developed the idea of atomic #’s Assigned one to each element based on the # of
protons in their nucleus Arranged elements according to the number of
protons instead of mass Now, elements are in a numerical repetitive order
as well as grouped according to their properties Since masses aren’t figured into arranging the
periodic table, it’s ok for them to be out of order
The Periodic Law
The periodic properties of the elements are functions of their atomic number.
In other words, the elements are arranged on the basis of their ground state electron configuration
Periodic Table of 1944
The Modern Periodic Table
Vertical Columns
The vertical columns are arranged in groups or families.
They are numbered from left to right
Elements in a group have the same electron structure in their outer subshell (valence electrons)
Electron Review
An electron shell, also known as a main energy level, is a group of atomic orbitals with the same value of the principal quantum number n.
Electron shells are made up of one or more subshell, which have orbitals with the same angular momentum quantum number l. (1 of s, 3 of p, 5 of d and 7 of f orbitals)
States with the same value of n are related, and said to lie within the same electron shell.
Example: 1s22s22p6 1s2 and 2s22p6 are in the same electron shell
States with the same value of n and also l are said to lie within the same electron subshell.Example: 1s22s22p6
1s2 are in the same electron subshell2s2 are in the same electron subshell2p6 are in the same electron subshell
Electron shells make up the electron configuration.
It can be shown that the number of electrons that can reside in a shell is equal to 2n2.
Shells and subshells are defined by the quantum numbers.
In large atoms, shells above the second shell overlap (Aufbau principle)
Valence Shell
The valence shell is the outermost shell of an atom, which contains the electrons most likely to participate in a chemical reaction with other atoms or to determine chemical properties.
Electrons in the valence shell are referred to as valence electrons.
Let’s see ...
Group 18
Ne =1s22s22p6
Ar = 1s22s22p63s23p6
Kr = [Ar]4s23d104p6
Xe = [Kr]5s24d105p6
Rn = [Xe]6s24f145d106p6
Further Breakdown
s-orbital elements d-orbital elements p-orbital elements
f-orbital elements
Horizontal Rows
The horizontal rows are the periods.
The periods are numbered from the top down.
Elements in the same period have the same principal energy level
Let’s see ...
Period 2 (Period n)
Li = 1s22s1 Be = 1s22s2 B = 1s22s22p1 C = 1s22s22p2
Group Names
Groups 1-2 and 13-18 (except Hydrogen) are the main group elements (also known as the representative elements).
Groups 3-12 are the transition metals
Specific Group Names
Group 1: alkali metals Group 2: alkaline earth metals Group 11: coinage metals (not IUPAC approved) Group 15: pnictogens (not IUPAC approved) Group 16: chalcogens Group 17: halogens Group 18: noble gases
Period Identifications
The elements in the 1st f-period are the Lanthanide series.
The elements in the 2nd f-period are the Actinide series
Group 1: Alkali Metals
Hydrogen is NOT included in Group 1
Metals that react with water to make an alkaline solution (basic)
Highly reactive, soft (less than 1 on the Mohs scale), and conductive
Group 1 Electrons
Not found in their elemental form but in compoundsexample: NaCl, KOH
There is only 1 valence electron. (ns1)
If the one electron is lost, it will be stable
Mohs Hardness Scale
The scale used to describe the hardness of a material is the Mohs Hardness Scale
The scale is from 0-10 (softest to hardest)example: Talc is 1 on the Mohs scale and the
Diamond is 10
Group 2: Alkaline Earth Metals
The alkaline earth metals are silvery colored, soft, low-density metals, which react readily with halogens to form ionic salts, and with water, to form strongly alkaline hydroxides.
Highly reactive, but not as reactive as alkali metals, usually found as compounds not in elemental form
Alkaline Earth Electrons
There are 2 valence electrons. (ns2)
It takes more energy to lose 2 electrons than it does to lose only one (like the alkali metals)
Valence Electrons of Groups 13-18 Group 13 = ns2np1 Group 14 = ns2np2 Group 15 = ns2np3 Group 16 = ns2np4 Group 17 (halogens) = ns2np5 Group 18 (noble gases) = ns2np6
Group 17: The Halogens
Halogens are highly reactive non-metals.
Only 7 valence electrons (just one short of a full and stable valence shell) so they want to gain an electron
Reactive with most metals to form salts
Group 18: Noble Gases
Have a full set of electrons (n2p6)
Low chemical reactivity and so they are very stable
Hydrogen
Hydrogen is in a class by itself because it is the most common element in the Universe!
Hydrogen only has one proton and one electron and can react with almost anything
Transition Metals
Groups 3-12 (d-block)
Do NOT have identical electron configurations in the outer shell. Why?The Lanthanide and Actinide series are
contained within the d-block and have f-orbitals
Lanthanide & Actinide
Lanthanide are the rare earth series from atomic #58 to #71shiny metals with similar reactivity to alkaline
Actinide are from atomic #89 to #103nuclei are unstable, radioactive
As you move to the right, electrons are filled in the f-orbital
Metallic Character
Approximately 2/3’s of the elements are metals.See periodic chart
Metals have unique properties: luster: mirror like shine that reflects lightconductivity: ability to conduct heat or electricitymalleable: ability to be rolled or hammeredductile: ability to be drawn into wire
Alloys
Metals that are mixed with other metals to form a stable compound are called alloysexample: Brass is Copper and Zincexample: Steel is Iron, Tin, Nickel, Lead, etc.
Nonmetals
Poor conductors of heat and electricity Not malleable Many are gasses
One is liquid – Br
Some are solids (brittle and dull) More electrons in outer level Form negatively charged ions
METALLOIDS
Metalloids – have properties of both
metals and nonmetalsOn the stairstep; exclude Aluminum and
Polonium