1.1 Atomic Structure

Ancient greek model of the atom

Atoms are tiny solid spheres which cannot be divided

JJ Thompson

Discovered the electron and developed the "plum-pudding" model of the atom

Plum pudding model of the atom

atoms are balls of positive charge with negative electrons embedded in it

Rutherford, Geiger, and Marsden

carried out alpha particle scattering experiment and developed the nuclear model of the atom

Alpha particle scattering experiment

Fired alpha particles at a thin sheet of gold foil.

Observations of the alpha particle scattering experiment

Most of the alpha particles went straight through the atom, a few bounced back

Conclusions of the alpha particle scattering experiment

Most of the atom is empty space except for a tiny positive nucleus

Nuclear model of the Atom

Atoms are made of a small positive nucleus orbited by negative electrons.

Niels Bohr

Suggested that electrons orbit the nucleus at specific distances

James Chadwick

Carried out experiments which provided evidence of neutrons

Relative mass of protons, neutrons and electrons

1, 1, 1/1840

Relative charge of protons, neutrons and electrons

+1, 0, -1

Why are atoms neutral?

same number of positive protons as negative electrons

Atomic number

the number of protons in the nucleus of an atom

Locations of subatomic particles

Protons/ neutrons- Nucleus

Electrons- Orbiting shells surrounding nucleus

Proton

has a positive charge, defines the type of atom and that is found in the nucleus

mass number (atomic mass)

number of protons + number of neutrons

Average atomic radius

0.1 nm (1 × 10^-10 m)

Average radius of an atomic nucleus

10,000 times smaller than an atom (1 x 10^-14 m)

Relative atomic mass

weighted average mass of an atom of an element

Relative atomic mass formula

(atomic mass*percentage abundance)+(atomic mass*percentage abundance)/(total percentage abundance)

Shells can hold

2, 8, 8 electrons

No of shells =

Period on the periodic table

What are valence electrons?

Outer shell electrons which are involved in reactions

No of valence electrons =

Group number on the periodic table

Hydrogen electron structure

1

Nitrogen electron structure

2,5

Argon electron structure

2,8,8

Potassium electron structure

2,8,8,1

Calcium electron structure

2,8,8,2

Aluminium electron structure

2,8,3

Magnesium electron structure

2,8,2

Oxygen electron structure

2,6

Fluorine electron structure

2,7

Carbon electron structure

2,4