Chemistry Chapter 4 Atomic Structure

Atom

The smallest particle of an element that retains its identity in a chemical reaction

Democritus

Greek philosopher (460-370 BC) believed that atoms were indivisible and indestructible

Dalton's Atomic Theory

1) All elements are composed of tiny indivisible particles called atoms
2) Atoms of the same element are identical.The atoms of any one element are different from those of any other element
3) Atoms of different elements can physically mix together or can

Scanning tunneling microscope

despite their small size, individual atoms are observable with instruments such as this

Electrons

Negatively charged subatomic particles

Cathode Ray

A stream of electrons produced at the negative electrode of a tube containing a gas at low pressure

Protons

Positively charged subatomic particles

Neutrons

Subatomic particle with no charge but with a mass nearly equal to that of a proton

Nucleus

the tiny central core of an atom and is composed of protons and neutrons

Atomic Number

The number of protons in the nucleus of an atom of that element

Mass Number

the total number of protons and neutrons in an atom

Number of neutrons

Mass number - atomic number = ?

Isotopes

Atoms that have the same number of protons but different numbers of neutrons

Atomic Mass Unit (amu)

A unit of mass equal to one-twelfth the mass of a carbon- 12 atom

Atomic Mass

A weighted average mass of the atoms in a naturally occurring sample of the element

Calculate Atomic Mass

mass of ea isotope X natural abundance (as a decimal), then add the products

Periodic table

An arrangement of elements in which the elements are separated into groups based on a set of repeating properties

Period

Each horizontal row of the periodic table

Group (family)

Each vertical column of the periodic table