History of the Periodic Table

Vocabulary Metal Shiny Non-Metal Ductile Period Malleable Properties Transition Elements Noble Gases Halogens Alkali Metals Alkaline Earth Metals Shiny Ductile Malleable Metalloids

Antoine Lavoisier In the late 1790s, he compiled a list of the known elements at the time. This list contained 23 elements. 1743 - 1794

But times were about to change… In the 1800’s, there were many changes in the world Electricity Spectrometer Industrial Revolution As a result, there was an increase in the number of known elements By the 1870, there were 70 known elements

An agreement is reached… Then in the 1860’s, chemist agreed upon a method for accurately determining the atomic mass of elements.

John Newlands Noticed when elements were arranged by atomic mass, they repeated properties every 8th element. He used the word periodic to describe this pattern He gave it the name the Law of Octaves 1838-1898

Unfortunately… Did not work for all the elements Criticized because of its association with music Did give others the idea of repeating properties - periodic We Hate It

Lothar Meyer and Dmitri Mendeleev 1834 - 1907 1830-1895 Each made a connection between atomic mass and properties of elements

The winner is… Mendeleev Mendeleev is given credit because his was published first In addition, Mendeleev predicted unknown elements However, not completely correct – new elements weren’t in correct order

Henry Moseley Solved this problem by arranging the elements by increasing atomic number. The periodic repetition of chemical and physical properties of elements when arranged by atomic number is now known as Periodic Law 1887-1915

Which leads to the Modern Periodic Table Boxes each with: Hydrogen Element Name 1 Atomic Symbol Atomic Number H Atomic Mass 1.00794 That are arranged by increasing atomic numbers

Remember Atomic number = the number of protons = the number of electrons (if neutral atom) Atomic Mass on the Periodic table is the average mass of the isotopes But the mass number of each isotope is the protons plus the neutrons

Chemical Symbol The symbol that refers to the element First letter is capitalized, second letter (if applicable) is lower case Not all symbols are based on English names for the elements, some come from their Latin names or even other languages – Tin – Sn – stannum – Iron – Fe - ferrum – Mercury – Hg - hydrargyrum – Gold – Au - aurum – Silver – Ag – argentum – Antimony – Sb -stibium – Lead – Pb – plumbum – Copper – Cu – cyprium

Columns and Rows The columns are called Families or Groups Earlier Version had 1-8 followed by A or B Group A elements are called Representative Elements Group B elements are called Transition Elements Modern Version labels the columns with 1-18 Rows are called Periods Seven periods for the seven energy levels (rings)

Classifying Elements Three Types of Elements Metals Nonmetals Metalloids

Metals Shiny when smooth and clean Solid at room temperature Only exception - Mercury Good conductors of heat and electricity Most are ductile and malleable

Most of the elements on the table are metals, which are in blue

Nonmetals Upper Right side of the Periodic Table Generally brittle solids or gases Poor conductors of heat and electricity Bromine is the only liquid at room temperature

“The Yellow Elements”

Metalloids A.k.a – the semi-metals Boxes bordering the stair-step Physical and chemical characteristics of both metals and nonmetals

“The Green Stair-stepping Elements”