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 elements; 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 number in a periodic way

Artificial Elements

trans-uranium 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

Atomic Radius

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

Trend for Atomic Radius

increases 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

increases from right to left and from top to bottom

Ionization Energy

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

Trend for Ionization Energy

increases from left to right and from bottom to 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

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

Linus Pauling

first chemist to quantify electronegativity

Descriptive Chemistry

the study of elements and the compounds they form

Hydrogen

Physical Properties: colorless, highly flammable gaseous element, the lightest of all gases, diatomic, and the most abundant element in the universe

Chemical Properties: similar to groups 1 and 17 because it only has one valence electron = very reactive

Alkali Metal Family

very chemically reactive

Physical Properties: good conductors/reactors, luster, low densities, soft at room temperature

Chemical Properties: react readily with water (one valence electrons); +1 ion

Alkaline Earth Metals 

Physical Properties: denser, harder, and have higher melting points than alkali metals; malleable and ductile

Chemical Properties: donate two electrons, reactivity increases down the column; +2 ion

Transition Metals

Physical Properties: very hard, high density, luster, conductive, with high melting and boiling points

Chemical Properties: found as pure solids in nature - except mercury (typically have 1 or 2 electrons)

Inner Transition Metals

Physical Properties: weakly magnetic, bright and silvery

Chemical Properties: actinide series = highly radioactive

Lanthanide series = “rare earth metals”

Groups 13-16

post-transition metals

Metalloids

have characteristics lying somewhere between those of metals and nonmetals; brittle, not very malleable, ductile, or conductive

Semiconductors

conduct electricity, but only under certain conditions

Boron Family (Group 13)

Physical Properties: ductile, malleable, luster (increases as you go down)

Chemical Properties: 3 valence electrons (will mostly give electrons); +3 ion

Carbon Family (Group 14)

Carbon is the backbone of living things

Physical Properties: solids at room temperature; carbon takes many forms; become more metallic as you go down

Chemical Properties: 4 valence electrons (reactive or non-reactive); +4 ion

The Nitrogen Family (Group 15)

Physical Properties: Nitrogen is normally diatomic

Chemical Properties: nitrogen gas is essentially inert; 5 valence electrons (very reactive, especially as you go down); -3 ion

The Oxygen Family (Group 16)

Physical Properties: oxygen exists as both O₂ and O₃ (most abundant element by mass in the earth’s crust)

Chemical Properties: 6 valence electrons; -2 ion

Halogen Family (Group 17)

chemically uniform group

Physical Properties: as their atomic numbers increase, their densities, boiling points, and melting points increase; very dangerous to living things

Chemical Properties: salt producing, 7 valence electrons (bond well with Alkali metals); -1 ion

Noble Gases (Group 18)

Physical Properties: colorless, odorless, tasteless

Chemical Properties: rarely react with other elements because they already have a full valence shell (8 valence electrons); no ions

Trend for Reactivity in Metals

increases from right to left and from top to bottom

Trend for Reactivity in Nonmetals

increases from left to right and from bottom to top

Periods Correspond to…

the maximum number of energy levels filled

Inert

not moving