I. Subatomic Particles(p.113 - 114)

Particle Symbol Location Charge Relative Mass (amu)

Actual Mass (g)

electron

proton

neutron

e-

p+

n0

Electron cloud

nucleus

nucleus

–

+

0

1/1840

1

1

9.11 x 10-28

1.67 x 10-24

1.67 x 10-24

approx 0

Elements are listed by their chemical symbols

Symbols are usually either one capital letter like C for Carbon, or one capital and one lowercase letter like Ne for Neon

The periodic table gives much information we need to learn more about the atom of each element

Atomic number = # of protons in an atom Whole number shown on periodic table Periodic table is arranged by atomic number

The average atomic mass is the number at the bottom of this square

Found by averaging the natural abundances of its isotopes

Weighted average

Atomic Number

Symbol

Element Name

Atomic Mass

Protons Electrons

Protons Neutrons

# n0 = Atomic mass – Atomic number

POSIT IVECHARG E

PROT ONS

NEUT RALCHARG E

NEUT RONS

NUCLEUS

NEG AT IVE CHARG E

ELECT RONS

AT OM

Most of the atom’s mass.

NUCLEUS ELECTRONS

PROTONS NEUTRONS NEGATIVE CHARGE

POSITIVE CHARGE

NEUTRAL CHARGE

ATOM

QUARKS#n0 = Atomic mass- Atomic #

equal in a neutral atomAtomic Number

equals the # of...

Quarks◦ component of

protons & neutrons

◦ 6 types

3 quarks = 1 proton or 1 neutron

He

II. How Atoms Differ (p. 114 - 121) Mass Number

Isotopes Relative Atomic Mass Average Atomic Mass

mass # = protons + neutrons

always a whole number

NOT on the Periodic Table!

© Addison-Wesley Publishing Company, Inc.

Atoms of the same element with different numbers of neutrons

C126

Mass #

Atomic #

Isotope notation:

Isotope name: carbon-12

Element name Mass #

© Addison-Wesley Publishing Company, Inc.

Chlorine-37◦ atomic #:

◦ mass #:

◦ # of protons:

◦ # of electrons:

◦ # of neutrons:

17

37

17

17

20

Cl3717

Isotope notation:

Most elements are found as mixtures of isotopes

Relative abundance of each isotope is the same in each source

12C atom = 1.992 × 10-23 g

1 p = 1.007276 amu

1 n = 1.008665 amu

1 e- = 0.0005486 amu

© Addison-Wesley Publishing Company, Inc.

atomic mass unit (amu)

1 amu = 1/12 the mass of a 12C atom

weighted average of all isotopes on the Periodic Table round to 2 decimal places

100

(%)(mass(mass)(%) )

Avg.AtomicMass

Avg.AtomicMass

EX: Calculate the avg. atomic mass of oxygen if its abundance in nature is 99.76% 16O, 0.04% 17O, and 0.20% 18O.

100

(18)(0.20)(17)(0.04))(16)(99.76 16.00amu

Avg.AtomicMass

EX: Find chlorine’s average atomic mass if approximately 8 of every 10 atoms are chlorine-35 and 2 are chlorine-37.

100

(37)(20)(35)(80)35.40 amu