3.1 Atomic Structure

Pages 70 - 76

Goal 1

Explain the historical progression of the atomic theory

• 400 BC Democritus

– Greek – “Happy philosopher”– Geometry pioneer– Astronomy

• Milky way

• Democritus’ atomic theory

– Real properties => perceived properties– Solid objects

• Pointy atoms• Hooks

– Liquid substances• Round• Slip

• 1808 John Dalton– England– Worked at college– Scientific research

• Numerical data• Widely accepted

• Dalton’s Atomic theory

1. Every element is made of tiny, unique particles called atoms that cannot be subdivided

2. Atoms of the same element are exactly alike

3. Atoms of different elements can join to form molecules

• 1903 JJ Thomson

– England

– Professor at Cambridge University

– Discovered electron

– Atoms are made up of smaller particles

• “plum pudding” of + and – charged particles scattered in jelly-like substance

• 1911 Ernest Rutherford– New Zealand– Professor in England Universities– Used alpha ray scattering and gold foil

• Rutherford’s atomic model: Mini solar system– Dense nuclei– Orbiting electrons

• 1913 Niels Bohr– Denmark– Copenhagen

University– Worked with

• Rutherford• Bohr• Planck• Einstein

• Bohr’s Atomic Model– Nucleus of heavy particles– Electrons orbit on set paths– Each path has its own energy level– Electrons must gain or lose energy to switch

paths

• Modern Atomic Model

– Nucleus of protons and neutrons– Electrons behave like waves on a vibrating

string– Cannot determine exact location of electrons– Electrons found in orbitals of energy levels– Valence electrons are outermost electrons

Goal 2

Explain the charge, mass, and location of each part of the atom according to the modern model

• Proton

– Charge +1

– Mass 1.67 x 10-27 kg

– Location nucleus

• Neutron

– Charge 0

– Mass 1.67 x 10-27 kg

– Location nucleus

• Electron

– Charge -1

– Mass 9.11 x 10-31 kg

– Location Orbitals around nucleus

• s orbital– Sphere shape– Surrounds nucleus– Holds max 2 electrons– 1st energy level (lowest)

• p orbital– Dumbbell shape– 3 dimensional orientation– Each dumbbell holds max 2 electrons (6 total)– 2nd energy level

• d orbital– 5 possible orbitals– 2 max electrons in each orbital (10 total)– 3rd energy level

• f orbital– 7 possible orbitals– Complex shape– 2 max electrons in each orbital (14 total)– 4th energy level (highest)

• Valence electrons– Outermost electrons– Important in bonding with other atoms– # can be found on your periodic table

6 24

carbon12.011

35 28

187

bromine79.904

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