Download Note Sheet 6 – Atomic Structure

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STUDIES IN SCIENCE
MATTER & ENERGY
Atomic Structure Notes
The Idea of the Atom

Democritus (79 AD)
o Greek philosopher
o “All matter is made of

A tomos means

Democritus thought
The Development of the Modern Atomic Model

John Dalton (1803)
o Each element has
o Atoms of

JJ Thompson (1897)
o Atoms are

Ernst Rutherford (1905)
o Gold Foil Experiment
o Most of the atom is
o There is a tiny bunch of

Niels Bohr (1911)
o Negatively charged particles
o The orbiting, negatively charged particles
Period:
The Modern Atomic Model

Subatomic particles –

There are three types of subatomic particles:
1. Protons (p+) –
2. Neutrons (n0) –
3. Electrons (e-) –

Nucleus –

Contains the

Nucleus contains _____ % of the mass of the atom

Electrons
Comparing Subatomic Particles
Particle
Location
Size & Mass
Charge
Proton (p+)
Neutron (n0)
Electron (e-)
Atoms are Neutral

Every atom has equal numbers of _______________ and _______________

Ex. Oxygen atoms

The negatives cancel out the positives
o 8 protons
=
_____ charge
o 8 electrons =
_____ charge
o Total charge =
_____
Electrons in Energy Levels

Electrons surround

The number of energy levels depends on
How many electrons in each level?

1st energy level holds _____ e-

2nd energy level holds up to _____ e-

3rd energy level holds up to _____ e-

Atoms with 2 e- or less have _____ energy
level

p+
n0
Atoms with 3 to 10 e- have _____ energy
levels

Atoms with more than 10 e- have at
least _____ energy levels
Valence Electrons

Valence electrons –

Valence electrons determine
o Will it

Ex. Oxygen atoms have 8 eo _____ in the 1st level
o _____ in the 2nd level
o How many valence e- does
an oxygen atom have? _____
Oxygen Atom
The periodic table gives information about 1 atom of any element

Atomic Number =
o Ex. 1 oxygen atom has _____ protons and _____ electrons

Mass Number =
o Ex. 1 oxygen atom has _____ protons + neutrons
o To figure out the number of neutrons subtract the _______________ from
the _______________
o 16 – 8 = 8, so an oxygen atom has _____ neutrons