atomic structure

Atomic Structure

Subatomic Particles

Empty Space

Subatomic Particle

Actual MassRelative

MassAtomic Mass

Units

Proton1.673 x 10-24

g1 1

Neutron1.675 x 10-24

g1 1

Electron9.11 x 10 -28

g1/1840

Approximately 0

•Atomic Mass Unit (AMU) = is defined as 1/12 the mass of a carbon – 12 atom

Atomic & Mass Number

• Atomic number:

• Mass number:

• Atomic Number = number of protons in nucleus

• Mass number = protons + neutrons

Number of electrons

• For a neutral atom:number of protons = number of electrons

• Atomic number:(# of protons)

• Number of electrons:

• Mass number:(p+ + n0)

Isotope Notation

• Atomic Number = number of protons in nucleus

• Mass number = protons + neutrons

• Number of neutrons = Mass number – atomic number

• Number of neutrons:

Examples

1. Neon – 20 – Protons:– Neutrons:– Electrons:– Atomic #:– Mass #:– Isotope Notation:

2. Iron – 56– Protons:– Neutrons:– Electrons:– Atomic #:– Mass #:– Isotope Notation:

Isotopes• Definition:

– Atoms of the SAME element, but different MASS

• What is different between these 3 atoms?

Atom OR Ion?

K

– Protons:– Neutrons:– Electrons:– Atomic #:– Mass #:

K+1

– Protons:– Neutrons:– Electrons:– Atomic #:– Mass #:

Atom OR Ion?

S

– Protons:– Neutrons:– Electrons:– Atomic #:– Mass #:

S-2

– Protons:– Neutrons:– Electrons:– Atomic #:– Mass #:

Band of Stability

Radioactive

• Low Mass– Elements 1-20

– Stable – n/p ratio = 1

– Unstable – Above or Below

• Middle Mass– Elements 21-83

– Stable – n/p ratio =• 1 to 1.5

Unstable – Above or Below

•NOTE: All atoms of elements above 83 are radioactive!!!

Radioactive

• Radioactive– Elements 84 and above

(all isotopes)– n/p ratio is too large

• Conclusions:– Number n0 = number p+ Stable– Atoms above or below this ratio Unstable– More mass Unstable (radioactive)

Radioactive

• Lithium - 8

• Number protons:• Number neutrons:

• n/p =

• Lead - 214

• Number protons:• Number neutrons:

• n/p =

Radioisotopes

• Definition:– a radioactive isotope of an element; produced

either naturally or artificially