History of Periodic Table

In the Beginning

• The first scientific discovery of an element occurred in 1649 when Hennig Brand discovered phosphorous.
• By 1869, a total of 63 elements had been discovered.
• As more and more elements were being discovered, scientists began to recognize patterns in properties.

• In 1863, John Newlands arranged chemical elements in order of their relative atomic masses and he arranged his elements in columns.



John Newlands

• He proposed the Law of Octaves in 1864
• This law stated that any element will show similar behaviours at the eighth element following it in the table.

Dmitri Mendeleev

• In 1864, Dmitri Mendeleev improved Newlands' idea and proved its effectiveness.
• Mendeleev is known as the 'father' of the periodic table.
• He organized the periodic table like no other chemist.
• He managed to organize them into groups possessing similar properties, not by atomic mass.
• He left gaps in the table, predicting that a new element would be discovered in place.

Mendeleev's Periodic Table

• In 1895, Lord Rayleigh discovered the gaseous element Argon.
• Did not fit with any of the periodic groups.
• In 1898, William Ramsey organize argon into the periodic table between chlorine and potassium.
• He made this decision even though argon's atomic weight was greater than potassium's.
• This group was called "zero" group due to the zero number of valence electrons in each element.
• He also predicted correctly properties such as neon.
• This groups is currently called the Noble Gases.

Modern Periodic Table

• Glenn Seaborg made the last major changes to the periodic table.
• Discovered plutonium in 1940
• Also discovered all elements from 94 to 102.
• Reconfigured table by moving the actinide series below the lanthanide series.
• Element 106 was name seaborgium (Sg) in his honor.
• The periodic table is completely organized by atomic number not by mass.
• Periodic Law: Elements recur periodically when arranged from lowest to highest atomic number.

Divisions in Periodic Table

• Period: horizontal rows
• Groups or Families: vertical columns
• Blocks: according to subshells (s-, p-, d-, and f-block)

Periodic Table Blocks

Chemical Families

• Alkali Metals
• Group 1
• Located in the s-block
• Highly reactive metals
• Alkaline Earth Metals
• Group 2
• Located in the s-block
• Share similar properties
• Relatively reactive metals
• Halogens
• Group 17
• Non-metal elements
• Contains all three familiar states of matter at a regular temperature and pressure.
• Highly reactive because the atoms are highly electronegative due to heir high nuclear charge.
• Reacts with water.
• Noble Gases
• Share similar properties
• All odorless, colorless, monatomic gases, with low chemical reactivity.
• Groups 18
• Outer shell full
• Lanthanide Series
• Includes 15 elements with atomic number 57 through 71.
• Are f-block elements
• Lanthanum and lutetium are labeled group 3 because they both have a single valence electron, therefor in the d-shell.
• Actinide Series
• Includes 15 elements from 89 to 103.
• Have similar properties.
• f-block elements
• Have a much more variable valence than the lanthanies.
• All radioactive and release energy during radioactive decay
• Can be used in nuclear reactors and nuclear weapons.

Modern Periodic Table