Periodic Table

History Antoine Lavoisier – Father of Modern Chemistry 1829 German J. W. Dobereiner Grouped elements into triads Three elements with similar properties Properties followed a pattern The same element was in the middle of all trends Not all elements had triads

Law of Octaves 1862 John Newlands developed Law of Octaves The elements showed a repetition in their chemical properties after 8 elements Used Atomic Weights but not actual values Important because showed the first pattern of repeating properties

Julius Lothar Meyer Meyer first table published 1864 containing 28 elements Arranged in order of Atomic Weight and made a clear horizontal relationship between Atomic Weight and Atomic Volume Allowed physical properties to outweigh chemical properties Anticipated Mendeleev by years

Meyer Left gaps to denote unknown elements Not willing to make predicitions More focused on Physical properties not chemical properties Bitter battle with Mendeleev Lost to Mendeleev because of Mendeleev’s forceful ways

Dmitri Mendeleev Mendeleev was known as the “Father of the Periodic Table” DOB: 1834-1907 Created the first table on 3-1-1869 Table had 70 elements Used properties to set up table

History Russian scientist Dmitri Mendeleev taught chemistry in terms of properties Mid 1800 – atomic masses of elements were known Wrote down the elements in order of increasing mass Found a pattern of repeating properties Not first to develop system but his version had the strongest impact

Mendeleev’s Table Grouped elements in columns by similar properties in order of increasing atomic mass Found some inconsistencies - felt that the properties were more important than the mass, so switched order. Found some gaps Must be undiscovered elements Predicted their properties before they were found

Mendeleev Distinguished from competitors by a devotion to, and love for, the individuality of the elements that went hand in hand with an intimate knowledge of their chemical characteristics Focused on both physical and chemical properties

Mendeleyev Cont. Chemical Properties Used: Atomic Weight vs. Valancey He could only predict these properties His work preceded chemical advances by 30 years Produced his table 27 years before the first subatomic particle, the electron was discovered Did not predict Noble Gases

Acceptance Mendeleev’s table received real acceptance in 1875 Discovery of Scandium, Germanium and Gallium showed Mendeleev’s predictions were correct.

“The elements were not being arranged to make a periodic table, but to fit the periodic table”

Meyer vs. Mendeleyev Julius Meyer (1830-1895) Created a table that plotted: Atomic Volume vs. Atomic Weight Lost out to Mendeleev Published before Meyer Final Table: Atomic Weight vs. Valency Table had 8 columns but was missing Noble Gases Discovered 30 years later

Modern Russian Table

Spiral Periodic Table

Changing of Table Henry Moseley (1887-1915) – changed table in 1913 by increasing atomic number Biggest Impact Glenn Seaborg – rare earth series from Actinium (89) up. Current Table Used Today Minor Changes – inner transitional Lu & Lr replaced La & Ac Bohr first linked Quantum Theory

Today’s Table

More History First Classified Groups: Gases Non-Metals Metals Earths First Elements Discovered: Carbon Sulfur Copper Gold & Silver Iron Tin Antimony Mercury Lead Oxygen (1772) First Classified Groups: Gases Non-Metals Metals Earths

The Modern Periodic Table Our current periodic table shows elements in order of increasing atomic number (#protons) Elements in the same column have similar properties, and are called a group or family. Groups are designated in two ways: A Roman numeral (I through VIII) and a letter (A or B) An Arabic number (1-18) A horizontal row of elements is a period. Elements in the same period have properties that tend to vary in a regular fashion. Periods are designated by an Arabic number (1-7).

Vertical Columns Known as Groups or a Family Elements in same group have similar physical & chemical properties Each group is identified by a group number and group letter

Groups and Periods Figure 2.19

Similar Properties in Groups Potassium metal reacts violently with water to producing a basic solution and flammable hydrogen gas. All alkali metals react with water to produce hydrogen gas. Figure 2.21

Classification of Elements Groups IA Alkali metals IIA Alkaline Earth Metals VIIA Halogens VIIIA Noble Gases Periods Metals, Nonmetals, Metalloids Main-group Elements, Transition Metals, and Inner-transition Metals. Figure from p. 73

Main-Group Elements and Transition Metals Main-group elements (also called representative elements) contain any element in the eight groups designated with the letter A. (In the Arabic numbering, groups 1, 2, and 13-18) Transition metals contain any element in the 10 groups designated with the letter B. (In the Arabic numbering, groups 3-12) Inner-transition metals contain the lanthanides and actinides listed separately at the bottom of the table.

Common Group Names Some groups have descriptive names that are commonly used instead of their group numbers. Alkali metals Group 1 (IA) metals (hydrogen is a nonmetal) are considered reactive because the react readily with other elements and compounds Alkaline earth metals Group 2 (IIA) metals are more reactive than the transition metals but less reactive than alkali metals

Common Group Names Some groups have descriptive names that are commonly used instead of their group numbers. Halogens Group 17 (VIIA) nonmetals exist naturally as diatomic molecules Noble gases Group 18 (VIIIA) nonmetals are also called inert gases are so named because they do not chemically react with other elements (with the exception of krypton and xenon)

The elements in the A groups are called the representative elements

Transition metals The Group B elements

IA IIA IIIB IVB VB VIB VIIB VIIIB IIIA IVA VA VIA VIIA VIIIA IB IIB 1 Other Systems IA IIA IIIB IVB VB VIB VIIB VIIIB IIIA IVA VA VIA VIIA VIIIA IB IIB 1 2 13 14 15 16 17 18 3 4 5 6 7 8 9 10 11 12 1A 2A 3A 4A 5A 6A 7A 8A 3B 4B 5B 6B 7B 8B 1B 2B

Horizontal rows are called periods There are 7 periods

Group 1A are the alkali metals Group 2A are the alkaline earth metals

Group 7A is called the Halogens Group 8 are the noble gases

The group B are called the transition elements These are called the inner transition elements and they belong here

Metals, Nonmetals, and Metalloids The periodic table has many classifications. Groups and periods are one classification. Another classification denotes metals, nonmetals, and metalloids. A stair-step line starting at boron (B) separates metals (to the left of the line) from nonmetals (to the right of the line). The metalloids exist along the line. Metalloids are elements that have physical properties resembling a metal, but the chemical reactivity of a nonmetal.

Metals

Metals & Their Properties Metals are good conductors of heat and electricity Metals are malleable Metals have high luster

Example of Metals Copper is a relatively soft metal and a very good electrical conductor Mercury is the only metal that exists as a liquid at room temperature

Non-metals

Nonmetals & Their Properties Carbon, the graphite in a pencil is an example of a nonmetallic elements Nonmetals are poor conductors of electricity Can be brittle Non-lustrous Many are gases at room temperature

Example of Nonmetals Sulfur was once known as Brimstone Microspheres of phosphorus, a reactive nonmetal

Metalloids or Semimetals Properties of both Semiconductors

Example of a Metalloid Silicon is a metalloid Silicon is brittle like a nonmetal Silicon has metallic luster Silicon is a semiconductor of electricity

Metals, Nonmetals, and Metalloids Figure 2.20

Chapter 2: Atoms, Molecules, and Ions Modern Periodic Table Elements are divided into two main classes EOS Chapter 2: Atoms, Molecules, and Ions

Chapter 2: Atoms, Molecules, and Ions Modern Periodic Table Except for hydrogen, those elements to the left of the line are metals EOS Chapter 2: Atoms, Molecules, and Ions

Chapter 2: Atoms, Molecules, and Ions Modern Periodic Table Elements to the right of the line are nonmetals EOS Chapter 2: Atoms, Molecules, and Ions

Chapter 2: Atoms, Molecules, and Ions Modern Periodic Table Elements around the line are referred to as metalloids EOS Chapter 2: Atoms, Molecules, and Ions