The Periodic Table of Elements

Early Versions 1830: 55 elements had been discovered

1860’s: Dimitri Mendeleev discovered a system that applied to all elements

Mendeleev

•Father of the periodic table•Noticed patterns when the elements were arranged by increasing atomic mass

Mendeleev Noted properties of elements

Melting point Density Color

Studied atomic mass and chemical bonds Compared mass to hydrogen

Mendeleev Noted that arranging elements

according to atomic mass did not always produce similar groups

Moved element cards into groups where they fit best

Predicted other elements and their properties

Mendeleev 1869: Published the 1st periodic table

The Modern Periodic Table

New elements were added as they were discovered

Early 1900’s: scientists learned about the atomic number

Reading the Periodic Table

Contains over 100

squares: one for each

element

Isotopes Atoms of a certain element ALWAYS have

the same # of protons….DO NOT always have the same mass May have different number of neutrons Isotope

Atoms of the same element that have a different number of neutrons

Isotopes Examples:

Chlorine-35 Chlorine-37 Carbon-14

Reading the Periodic Table

An element’s properties can be predicted from its location on the periodic table.

groups/familiesperiods

Groups/Families Elements in columns 18 columns Elements in each group have

similar characteristics. Example: Group 1 are metals that all react violently with water; Group 17 reacts violently with elements from Group 1; Group 18 rarely reacts at all

Groups/Families EXAMPLES OF FAMILIES

- Alkali Metals- Alkaline Earth Metals- Transition Metals- Halogen Gases- Inert Gases (Noble Gases)

Periods Horizontal rows Series of different elements from different groups

Have very different properties

Why it Works!It’s based on the structure of atoms, especially the valence electrons!

Metals Most elements are metals. Found to the left of the zig-zag line. Elements are classified as metals

based on physical properties. Hardness Shininess (luster) Malleability Ductility

Physical Properties Have luster (shiny) Good conductors of heat &

electricity (transmit easily) High density Very high melting point Ductile (drawn into thin wires) Malleable (hammered into thin

sheets) Most are solid at room temperature.

Chemical Properties

Wide range of chemical properties Some are very reactive and combine

quickly. (sodium) Some are unreactive. (gold) Other metals fall somewhere in

between Corrosion: the process of reaction and

wearing away of metals

Alloys A mixture of metals Combine the best properties of

2 or more metals into a single substance

Ex: copper + tin = bronze Ex: copper + zinc = brass

Group 1: Alkali Metals

From Lithium to Francium MOST reactive of ALL metals NEVER found uncombined in nature; exist as compounds

Very soft & shiny Have 1 valence electron (lose easily)

2 MOST IMPORTANT: sodium & potassium (essential for life)

Group 2: Alkaline Earth Metals

Not as reactive as group 1, but still more reactive than most metals

NEVER found uncombined in nature Have 2 valence electrons (lose easily) 2 MOST COMMON: magnesium &

calcium Magnesium: flash bulbs, alloys for

airplanes, ladders Calcium: teeth & bones, muscles

Groups 3-12: Transition Metals

Form a bridge between very reactive metals on the left and less reactive metals on the right

So similar to one another that differences between nearby columns are difficult to detect

Include the most familiar metals: iron, copper, nickel, silver & gold

Groups 3-12: Transition Metals

Most are hard and shiny All are good conductors of

electricity. Fairly stable, reacting slowly or

not at all with water and air

Groups 13-16: Metals in Mixed Groups

Metals to the right of the transition metals are not nearly as reactive as those on the left.

Most familiar: aluminum, tin, lead

Lanthanides and Actinides

Lanthanides: top row at the bottom of the periodic table

Actinides: bottom row at the bottom of the periodic table

Called rare earth elements Fall between alkaline earth metals and

transition metals Placed at the bottom for convenience

Lanthanides Soft, malleable, shiny metals High conductivity Used in industry to make various

alloys Different lanthanides are found

together in nature; difficult to separate because of the similar properties

Actinides Only thorium and uranium exist on

Earth in any significant amounts Uranium: used in nuclear power

All elements after uranium were created artificially in a laboratory.

NonmetalsLack most of the properties of metals

Located to the right of the zigzag line

Physical Properties In general: opposite of metals Gases at room temperature; means they

have low boiling points Dull Solid nonmetals are brittle. NOT malleable or ductile Lower densities than metals Poor conductors of heat and electricity

Chemical Properties

Readily form compounds; except Group 18

Group 18 elements do not react with other elements.

Many form molecules containing 2 atoms: diatomic molecules (O2)

Nonmetals can form compounds with metals (NaCl) or other nonmetals (CO2).

Families of Nonmetals

Carbon Family (Group 14) All have 4 valence electrons. Carbon is the only nonmetal in the group. 2 are metalloids; 2 are metals Carbon is special because it is important for life. ALL living things contain Carbon!

Families of Nonmetals

Nitrogen Family (Group 15) All have 5 valence electrons. Only 2 nonmetals in this group: nitrogen &

phosphorus N2 makes up about 80% of our air; most

living things can not use it in gas form Get nitrogen from food Phosphorus is not a stable element; always

found in compound in nature. Used to make matches and flares

Families of Nonmetals

Oxygen Family (Group 16) All have 6 valence electrons. Elements typically gain or share 2 electrons Oxygen we breathe = O2 Ozone = O3 Oxygen is very reactive and can combine easily

with other elements. Oxygen: most abundant element in Earth’s crust;

second most abundant in the atmosphere Sulfur is a common nonmetal in the Oxygen family

Families of Nonmetals

Halogen Family (Group 17) All have 7 valence electrons. All but Astatine are nonmetals; Astatine is a

metalloid Typically gain or share 1 electron ALL are very reactive; most are dangerous to

humans Compounds that they form are useful:

Flourine—toothpaste, nonstick cookware Chlorine—table salt Bromine—reacts with silver (photographic film)

Families of Nonmetals

Noble Gases (Group 18) Also known as inert gases ALL have 8 valence electrons Do Not ordinarily form compounds Do not gain, share, or lose electrons; very

stable and unreactive All exist in Earth’s atmosphere, but only in

small amounts

Families of Nonmetals

Hydrogen Simplest of all elements Generally contains only one proton and one electron Cannot be grouped in a family because its chemical

properties are so different from other elements Makes up 90% of the atoms in the universe; only 1%

of the mass of Earth’s crust, oceans, & atmosphere Rarely found on Earth as an element Mostly combined with oxygen (water)

Metalloids On zigzag line between metals & nonmetals 7 elements Some have characteristics of metals; some

have characteristics of nonmetals Most useful property is their varying ability

to conduct electricity Most common is silicon

Sand, glass, cement

Metalloids Whether they conduct electricity

depends on temperature, exposure to light, or presence of impurities

Semiconductors: substances that under certain conditions can carry electricity, while under others it cannot Silicon & germanium Used to make computer chips, transistors,

lasers