unit 3 – periodic table of elements

All content by HST Educational Innovations © 2012. All rights reserved. Use of this material is invited with proper attribution to the source.All content by HST Educational Innovations © 2012. All rights reserved. Use of this material is invited with proper attribution to the source.

Unit 3 – Periodic Table of Elements

All content by HST Educational Innovations © 2012. All rights reserved. Use of this material is invited with proper attribution to the source.

Early Development of the Periodic Table of Elements• Antoine Lavoisier • John Dalton • Jacob Berzelius • Johann Dobereiner• John Newlands


Development of Modern Periodic Table of Elements

• Dmitri Mendeleev (Russia 1864)• Produced the first Periodic Table to arrange elements in periods

(rows) and families (columns) showing all 66 known elements• Periods arranged elements in order of increasing atomic mass• Families arranged by similar chemical and physical properties• Method of arrangement left gaps for elements believed to exist and

not yet discovered.• William Ramsay • Henri Becquerel• Frederick Soddy • J.J. Thomson


Mendeleev’s Periodic Table


Development of Modern Periodic Table of Elements (cont.)• Henry Moseley (England 1913)

• Demonstrated through x-ray spectroscopy that the characteristics of the x-rays emitted by different atoms are incremental and can be listed in numerical order (Atomic Number)

• Put forward the theory that chemical and physical properties are periodic functions of this atomic number (Law of Periodicity)

• Refined Rutherford’s theory of the atomic structure indicating a correlation between the positive charge of the nucleus and atomic number

• Developed the basic structure of the Periodic Table used today.• Rutherford


Moseley’s Periodic Table

Image courtesy of http://corrosion-doctors.org/Periodic/Periodic-Moseley.htm


Development of Modern Periodic Table of Elements (cont.)• Glenn Seaborg ( United States 1941-1944)

• Discovered discrepancies in Moseley’s table through the identification of new elements while conducting research as part of the Manhattan Project

• Created the lanthanide and actinide series referred to as transuranium elements

• Discoveries disclosed at the end of World War II• Continuing research

• Research laboratories use particle accelerators to identify new elements

• Recent discoveries have completed the 7th period of the table• Research is continuing to discover more new elements in an 8th

period


Seaborg’s Periodic Table


Periodic Table of Elements 2012

Image used courtesy of https://proteabio.com/resources/tools/Periodic+Table+of+Elements


Dynamic Periodic Table

• Courtesy of ptable.com

Image courtesy http://www.fanpop.com

http://ptable.com/


Families of Particular ImportanceFamily 1A (1) – Alkali Metals

Soft metals and silver gray in color Extremely reactive – do not exist in elemental form in nature 1 valence electron

Family 2A (2) – Alkaline Earth Metals Soft metals and silver in color Very reactive – can exist in nature, but oxidize rapidly 2 valence electrons

Family 7A (17) – Halogens (non-metals) Very reactive Lighter halogens are gases at room temperature while heavier halogens are solids

at room temperature; Bromine is a liquid at room temperature 7 valence electrons

Family 8A (18) – Noble Gases (Non-metals) Generally non-reactive and do not form compounds Extremely Stable 8 valence electrons


Types of ElementsMetals

Good conductors of electricity and heatVast majority of the elements – Alkali metals, alkaline earth metals,

transition metals, post-transition metals, and inner transition metals

Non-MetalsPoor conductors of electricity and heatIncludes the Nobel Gases, Halogens, and only a few of the lightest

elements – hydrogen, carbon, nitrogen, oxygen, phosphorus, sulfur, and selenium

MetalloidsMany are semiconductors of electricityExhibit properties of both metals and non-metalsOnly 7 elements are metalloids (some scientists include different ones

depending on perspective)


Periodic Law Created by Henry Moseley

The chemical and physical properties of the elements are periodic functions of their atomic numbers

Properties of the elements occur at repeated intervals called periods (rows on Periodic Table)

This defines the property of periodicity


Periodic TrendsAtomic Radius – half the distance between the nuclei of atoms of

the same materialDecreases generally across periods – increased positive nuclear

charge (protons) pulls electrons in tighter to the nucleusIncreases generally down families – increased number of energy

levels where electrons may reside

Electronegativity – the measure of the ability of the nucleus of an atom to attract electrons of a neighboring atomIncreases generally across periods – increased positive nuclear charge

(protons) more strongly attracts electrons from neighboring atomsDecreases generally down families – increased number of energy

levels means the nucleus is less able to overcome the distance between atom


Periodic TrendsIonization Energy – the energy required to remove an electron

from an atomIncreases generally across periods – increased positive nuclear charge

(protons) pulls electrons in tighter to the nucleus making them harder to remove

Decreases generally down families – increased number of energy levels where electrons may reside making them easier to remove

Ionic Radius – as atoms gain and lose electrons, the radius of the charged atom changesIncreases when an atom accepts electrons– the more electrons there

are the greater the overall repulsive forces between the electrons pushing them further apart

Decreases when an atom loses electrons – the fewer the electrons the greater the effectiveness of the nuclear charge (protons)


Periodic Trends

unit 3 – periodic table of elements

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