Chemistry Chapter 6 - The Periodic Table

What does the history of the development of the periodic table demonstrate?

The process of model making in science

Antoine Lavoisier

published a list of thirty substances that he called “elements” (1793); some of his elements were actually compounds; grouped based on properties

John Dalton

eventually documented as many as sixty elements; complex symbol system; organized by relative atomic weight

Johann Dobereiner

triads: families of three grouped by similarities in the properties of element; periodicity: measurable property regularly repeats itself sequentially 

John Newlands

Law of Octaves: pattern in mass and properties was observed when arranged in eight groups of seven

Dmitri Mendeleev

“Father of the periodic table” - elements arranged by atomic masses; organized elements that were not yet discovered (transition metals)

Mendeleev’s Periodic Law

properties of elements vary with their atomic masses in a periodic way

Henry Moseley

developed the modern periodic law

Modern Periodic Law

properties of elements vary with their atomic numbers in a periodic way

Artificial Elements

transunranium elements: atomic number greater than 92; neptunium and plutonium are the only ones found in nature, others are products of artificial processes

Vertical column on the periodic table

Group or family

Horizontal row on the periodic table

Period or series

Metals are found on the…

left and middle of the periodic table

Nonmetals are found on the…

right side of the periodic table

Metalloids

share properties of both metals and nonmetals

Atomic Radius

distance from the center of the atom’s nucleus to its outermost electrons (determined by electron cloud)

Trend for Atomic Radius

radii increase in size going from right to left and from top to bottom

Ionic Radius

cations are smaller than their parent atoms; anions are larger than their parent atoms

Trend for Ionic Radius

tends to increase as you move from top to bottom and from right to left

Ionization Energy

a measure of the difficulty of removing an electron from an atom or ion

Trend for Ionization Energy

generally increases from left to right and from bottom top (no noble gases)

Electron Affinity

the amount of energy required to add an electron to a neutral atom to form a negative ion (opposite of ionization energy)

Trend for Electron Affinity

increases from left to right and from bottom to top (no noble gases)

Electronegativity

the measure of the attraction between the nucleus and shared valence electrons

Trend for Electronegativity

increase from left to right and from bottom to top (no noble gases)

Linus Pauling

first chemist to quantify electronegativity