Elements

• Elements – pure substance that cannot be broken down by physical or chemical means

• Pure substance – a substance that contains only one type of particle.

• Elements have characteristic properties that do not depend on amount of material present

• Most elements are combined in nature

– Examples

• H2O (water)

• CaF2 - fluorite

Atoms

• HaveProtons – positive

charged particles

Neutrons – neutral charged particles

Protons and neutrons are found in center of atom, called a nucleus

Atoms

• Surrounding nucleus are

Electrons – negative charge particles

This region is called the electron cloud or energy levels

Atoms

• Atomic number- number of protons in the nucleus

• Mass number (atomic mass)- number of protons plus neutrons

Isotopes

• The number of protons in an element never changes.

• The number of neutrons in an element may change.

• Isotope- a variation of an element that differs only in the number of neutrons.

• Examples (hydrogen):– protons neutrons

1 0 (hydrogen) 1 1 (deuterium- heavy water) 1 2 (tritium- radioactive)

Metals

• Shiny• Good conductors of

heat and electricity• Malleable – flattened

into thin shapes• Ductile – drawn into

thin wires• Can be solid or liquid• Copper, lead and tin

are examples

Nonmetals

• Dull (not shiny)• Poor conductors of

heat and electricity• Brittle• Can be solid,

liquid or gas• Bromine, sulfur and

neon are examples

Metalloids

• Have properties of metals and nonmetals

• Many are called semiconductors

• Dull or shiny• Some can be

malleable or ductile• Examples include

antimony, silicon, boron

Dmitri Mendeléev

• In 1869, Dmitri Mendeléev created the first version of the periodic table.

• Grouped elements based on atomic mass

• Found elements in same group had similar chemical properties. 

• Blank spaces were left open to add the new elements

• Just over 50 elements were known then.

The Periodic Table

Rows = Periods

-no similar properties

-1st element = reactive metal

-last element = non reactive gas

Columns = Groups/Families

-have similar properties

-have same number of valence electrons

- examples lithium, sodium and potassium

Hydrogen

-single element with its own classification

-sits atop Group IA

-1 electron in its only energy level

IA

Alkali Metals

-Group IA elements, excluding hydrogen (all metals)

-always combined with other elements in nature

-1 electron in its outer energy shell

IA

Alkaline Earth Metals

-Group IIA elements (all metals)

-always found combined with other elements in nature

-2 electrons in its outer energy shell

IIA

Transition Elements

-Group B elements (all metals)

-many found combined with other elements in nature, some found in their elemental state (gold and silver)

-varying numbers of electrons in outer energy shell

B

Boron Family

-Group IIIA elements (boron = metalloid, rest are metals)

-always found combined with other elements in nature

-3 electrons in its outer energy shell

IIIA

Carbon Family

-Group IVA elements (nonmetal, metalloids and metals)

-mostly found combined with other elements in nature but may be found in its elemental state (e.g. diamond and graphite)

-4 electrons in its outer energy shell

IVA

Nitrogen Family

-Group VA elements (nonmetals, metalloids and a metal)

-mostly found combined with other elements in nature

–5 electrons in its outer energy shell

VA

Oxygen Family

-Group VIA elements (nonmetals, metalloids and a metal)

-mostly found combined in nature but may be found in its elemental state (e.g. sulfur)

-6 electrons in its outer energy shell

VIA

Halogens

-Group VIIA elements (nonmetals and a metal)

-mostly found combined with other elements in nature

-7 electrons in its outer energy shell

VIIA

Noble Gases

-Group VIIIA elements (nonmetals)

-never found combined with other elements in nature

-contain a full set of electrons in its outer energy shell

VIIIA

Rare-Earth and Radioactive Elements

-the last two rows of the Periodic Table

-Lanthanide series (rare-earth elements)

-Actinide series (radioactive elements- most are human-made)

B