Particles in the Atom Each element is chemically unique. To understand why they are unique, you need to know the structure of the atom (the smallest particle.

ElectronsElectrons (-) charge no mass located outside the nucleus

ProtonsProtons (+) charge 1 amu located inside the nucleus

NeutronsNeutrons no charge 1 amu located inside the nucleus

Particles in the Atom

Discovery of the Neutron

James Chadwick bombarded beryllium-9 with alpha particles, carbon-12 atoms were formed, and neutrons were emitted.

n10

+He42

+Be94 C12

6

Dorin, Demmin, Gabel, Chemistry The Study of Matter 3rd Edition, page 764 *Walter Boethe

Subatomic particles

Electron

Proton

Neutron

Name Symbol ChargeRelative mass

Actual mass (g)

e-

p+

no

-1

+1

0

1/1840

1

1

9.11 x 10-28

1.67 x 10-24

1.67 x 10-24

Subatomic Particles

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.

NUCLEUSNUCLEUS ELECTRONSELECTRONS

PROTONSPROTONS NEUTRONSNEUTRONS Negative Charge

PositiveCharge

NeutralCharge

ATOM

QUARKSAtomic Numberequals the # of...

equal in a neutral atom

Courtesy Christy Johannesson www.nisd.net/communicationsarts/pages/chem