1. History of The Periodic Table

2. Objectives Explain how elements are organized in a periodic table Explain how elements are organized in a periodic table Compare early and modern periodic tables Compare early and modern periodic tables Identify 3 broad classes of elements Identify 3 broad classes of elements

3. Important Vocabulary Triad Triad Law of Octaves Law of Octaves Periodic Law Periodic Law Group Group Period Period Malleable Malleable Ductile Ductile Metalloid Metalloid

4. Searching for an Organizing Principle By 1700, only 13 elements had been identified By 1700, only 13 elements had been identified By the decade of 1765-1775, 5 new elements had been discovered with the increased use of the scientific method By the decade of 1765-1775, 5 new elements had been discovered with the increased use of the scientific method However, as more elements were discovered in the years following, a need for a classification system became important However, as more elements were discovered in the years following, a need for a classification system became important

5. J.W. Dobereiner In 1829, this German chemist published a classification system In 1829, this German chemist published a classification system Within his system, element were grouped into triads Within his system, element were grouped into triads A triad is a set of 3 elements with similar properties A triad is a set of 3 elements with similar properties Problem: all the known elements could not be grouped into triads Problem: all the known elements could not be grouped into triads

6. John Newlands Was an English chemist Was an English chemist In 1865, he arranged the known elements according to their properties and in order of increasing atomic mass In 1865, he arranged the known elements according to their properties and in order of increasing atomic mass In doing this he noticed that all the elements in a given row had similar chemical and physical properties In doing this he noticed that all the elements in a given row had similar chemical and physical properties It seemed that this pattern repeated every eight elements It seemed that this pattern repeated every eight elements He called this observed pattern the law of octaves He called this observed pattern the law of octaves

7. John Newland’s Periodic Table

8. Dmitri Mendeleev Was the inventor of the first periodic table in 1869 Was the inventor of the first periodic table in 1869 He was a Russian chemist who used Newland’s observations and other information to create a table arrangement He was a Russian chemist who used Newland’s observations and other information to create a table arrangement His table only had 63 elements His table only had 63 elements

9. Creating the 1 st Periodic Table He wrote a symbol for each element, along with the physical and chemical properties and the relative atomic mass of the element on cards He arranged the elements in order of increasing atomic mass He started a new row everything he notices the elements chemical properties repeated In addition, he left gaps in his table for elements he predicted should fit there

11. Henry Moseley Was an English chemist Was an English chemist In 1914, he found a different physical basis for the arrangement of the elements In 1914, he found a different physical basis for the arrangement of the elements He studied the X-ray spectra of 38 different elements and found that the wavelengths of the lines in the spectra decreased in a regular manner as atomic mass increased He studied the X-ray spectra of 38 different elements and found that the wavelengths of the lines in the spectra decreased in a regular manner as atomic mass increased He ultimately developed the concept of atomic number He ultimately developed the concept of atomic number Thus, the periodic table was arranged by atomic number rather than atomic mass Thus, the periodic table was arranged by atomic number rather than atomic mass

12. Periodic Law States that when the elements are arranged according to their atomic numbers, elements with similar properties appear at regular intervals States that when the elements are arranged according to their atomic numbers, elements with similar properties appear at regular intervals So why does this happen? So why does this happen? It has to do with the electron configurations of elements It has to do with the electron configurations of elements

13. Organization of the Periodic Table Elements in each column of the table have the same number of electrons in their outer energy level. Elements in each column of the table have the same number of electrons in their outer energy level. These outer electrons are called valence electrons These outer electrons are called valence electrons A vertical column on the periodic table is called a group A vertical column on the periodic table is called a group Where as a horizontal row on the periodic table is called a period Where as a horizontal row on the periodic table is called a period

14. 3 Main Groups of Elements Elements are classified into 3 main groups Metals Nonmetals Metalloids (aka Semiconductors)

15. Metals There are 6 types of metals in the periodic table There are 6 types of metals in the periodic table Alkali metals Alkaline-earth metals Transition metals Rare Earth metals Synthetic metals Other metals

16. Characteristics of Metals Many elements are classified as metals Many elements are classified as metals Most of them are located in the middle of the periodic table Most of them are located in the middle of the periodic table Metals are good conductions of heat & electric current Metals are good conductions of heat & electric current They are malleable and ductile They are malleable and ductile Malleable means that they are easily formed Malleable means that they are easily formed Ductile means that they can be drawn into wires Ductile means that they can be drawn into wires Metals also have luster Metals also have luster

17. Nonmetals Are found throughout the periodic table Are found throughout the periodic table Groups 13-16, 17 & 18 and hydrogen Groups 13-16, 17 & 18 and hydrogen They are poor conductors of heat and electric current They are poor conductors of heat and electric current Only exception to this rule is carbon Only exception to this rule is carbon Solid nonmetals tend to be brittle and will shatter if hit with a hammer Solid nonmetals tend to be brittle and will shatter if hit with a hammer What elements do they include? What elements do they include?

18. Semiconductors Are intermediate conductors of heat & electricity Are intermediate conductors of heat & electricity Also known as metalloids Also known as metalloids Include only 7 elements: Boron, Silicon, Germanium, Arsenic, Antimony, Tellurium and Astatine Include only 7 elements: Boron, Silicon, Germanium, Arsenic, Antimony, Tellurium and Astatine Silicon is the most familiar semiconductor Silicon is the most familiar semiconductor What is it used for? What is it used for?