Subatomic Par-cles, The Periodic Table and Isotopes

Dene an isotope and explain the role of atomic number in

determining the iden-ty of an atom

Atomic Theory Atomic Structure Atom is composed of subatomic par-cles:

Neutron (neutral) Proton (posi-ve) Electron (nega-ve)

Atomic number (Z) the number of protons is a nucleus The number of electrons (in a neutral form, no charge)

Isotopes atoms of a single element (same atomic number) that dier in the number of neutrons in their nuclei (dierent masses)

Atomic number = # protons = # electrons

Isotopes atoms of a single element (same atomic number) that dier in the number of neutrons in their nuclei (dierent masses)

+ -

+ -

+ -

Pro$um deuterium tri$um

+ -

+ -

+ -

Pro$um deuterium tri$um

Mass number (A) the combined number of protons and neutrons A = Z+N

H A1 Z 1 H ? ?

Atomic mass= neutrons +protons

Protons? Electrons? Neutron?

A = Z+N

12 6 C

Protons? 6p+ A=Z+N Electrons? 6e- 12 = 6+N Neutron? 6n N=6

A = Z+N

12 6 C

Carbon-12 (Hyphen nota-on)

Protons? Electrons? Neutron?

A = Z+N

13 6 C

Protons? 6p+ A=Z+N Electrons? 6e- 13 = 6+N Neutron? 7n N=7

A = Z+N

13 6 C

Carbon-13 (Hyphen nota-on)

Protons? Electrons? Neutron?

A = Z+N

235 92 U

235 92 U Protons? 92p+ A=Z+N Electrons? 92e- N=235-92 Neutron? 143n N=143

A = Z+N

Rela-ve Atomic Mass Chlorine exists as two isotopes: chlorine-35 and chlorine-37.

When we calculate the rela-ve atomic mass of an element we have to take into account the propor-ons of each isotopes present.

In a naturally occuring sample of chlorine, we nd that 75% is chlorine-35 atoms and the other 25% is chlorine-37 atoms. What is the rela-ve atomic mass?

What is the rela-ve atomic mass of thallium which is made up from 30% thatllium-203 and 70% thallium-205?