Chapter 4 – 1 Atoms and the Periodic Table Atomic Structure

What are atoms? Democritus – universe made of invisible units called atoms Atom – “unable to divide” No real proof

Atomic Theory John Dalton – atoms cannot be divided 1800’s – English School Teacher Atoms of a given element are alike Atoms of different elements can form compounds

Parts of an Atom Nucleus – central region that is made of protons and neutrons Proton – subatomic particle Positive Charge In nucleus

Parts of an Atom Neutron – subatomic particle No charge or neutral Found in nucleus Electron – subatomic particle Negative charge Found outside nucleus

Quarks Protons and Neutrons are made of smaller particles called quarks.

No Charge Atoms are not charged Equal number of protons and neutrons Charges cancel

Bohr’s Model Niles Bohr – electrons move in set paths around nucleus Planets in the solar system Electrons have a certain energy that determines its path

Bohr’s Model Gain energy farther out Lose energy closer in

Electron Location Electron Cloud - Impossible to determine the exact location of an electron Area where they most likely are

Electron Energy Level 1st level – 2 electrons 2nd level – 8 electrons 3rd level – 18 electrons 4th level – 32 electrons

Orbital Orbital – region in atom where there is a high probability of finding electrons Electrons occupy orbitals with lowest energy

Orbital 4 kinds of orbitals: s, p, d, and f S – sphere shape Lowest energy 2 electrons

Orbital P – dumbbell shaped Orientated 3 ways in space More energy that s Each p holds 2 electrons 3 p = total of 6 electrons

Orbital D and F orbital – more complex D – 5 possible orientations F – 7 possible orientations Each hold a maximum of 2 electrons

Valence Electrons Valence Electrons – found in the outermost shell of an atom Determines chemical properties