Atomic Structure

Section 3.1, p.70-76

Hydrogen

• Atomic number: 1• Name: Hydrogen• Symbol: H• Family: Nonmetals

• Commonly combines with itself to form a diatomic molecule, H2

Democritus’ Model of the Atom

• 4th Century B.C. to 1808• “The universe is made of invisible units called

atoms.”• “The movements of atoms cause changes in

matter”

Helium

• Atomic number: 2• Name: Helium• Symbol: He• Family: Noble gases

• Recovered from oil drilling operations where radioactive alpha particles combine with free electrons to form the element.

Dalton’s model of the Atom

• 1808 to 1913• “Every element is made of

tiny, unique particles called atoms that cannot be subdivided.”

• “Atoms of the same element are exactly alike.”

• “Atoms of different elements can join to form molecules.”

Lithium

• Atomic number: 3• Name: Lithium• Symbol: Li• Family: Alkali Metals

• Used in the aerospace industry as a compound that absorbs poisonous carbon dioxide from manned space capsules (LiOH)

Bohr’s Model of the Atom

• 1913 to 1925• “Electrons move in set paths

around the nucleus much like the planets orbit the sun in our solar system.”

• “Each electron has a certain energy determined by its path, which is its energy level.”

• “Electrons can only have certain energy levels.”

Beryllium

• Atomic number: 4• Name: Beryllium• Symbol: Be• Family: Alkaline Earth Metals

• Found in nature as part of a compound in precious and semi-precious stones such as aquamarine and emerald

Modern Theory of the Atom

• 1925 to present• “Electrons behave more like waves on a

vibrating string than they do like particles.”• “Electrons are found in ORBITALS within

energy levels.”

Valence Electron (outermost energy level)

protons

neutrons

Electron Cloud

Boron

• Atomic number: 5• Name: Boron• Symbol: B• Family: Nonmetal Semiconductor

• A component of the compound Borax, which is an ingredient in detergent and cosmetics. In some countries, it is used as a food additive similar to salt, but is banned for this purpose in the U.S. Some foods containing it include French and Iranian caviar.