Atomic Structure

The Structure of the Atom The Ancient Greeks used to believe that everything was made up of very small particles. I did some experiments in 1808 that proved this and called these particles ATOMS: John Dalton ELECTRON – negative, mass nearly nothing PROTON – positive, same mass as neutron (“1”) NEUTRON – neutral, same mass as proton (“1”)

The Nucleus is made of Protons and Neutrons The Atom Electron Nucleus Shell or Orbit

Hydrogen has one proton, one electron and NO neutrons The Hydrogen Atom Hydrogen has one proton, one electron and NO neutrons Proton Electron

Helium has two electrons, two protons and two neutrons The Helium Atom Helium has two electrons, two protons and two neutrons Proton Electron Neutron

Sub-Atomic Particles 2 He 4 Particle Mass Charge Proton 1 Neutron Electron -1 ATOMIC NUMBER = number of PROTONS He 2 4 SYMBOL MASS NUMBER = number of PROTONS + number of NEUTRONS

The Helium Atom 2 He 4 Proton Electron Neutron Atomic Number 2 = 2 Protons 2 He 4 Atomic Mass 4 = 2 Protons + 2 Neutrons

The number of Protons is ALWAYS equal to the number of ELECTRONS # Protons = # Electrons The number of Protons is ALWAYS equal to the number of ELECTRONS Li 3 + Protons 3 - Electrons

Electron Orbit: Bohr Model Electrons have fixed orbit ‘shells’ The first shell can carry TWO electrons All other shells can carry EIGHT electrons at most

Valence Electrons Valence Electrons are located on the OUTERMOST Shell, and determine how REACTIVE an element is

The Atom Li - Lithium Li has 3 protons, 3 electrons, and 4 Neutrons

Boron has five protons, five electrons and six neutrons. The Atom B - Boron Boron has five protons, five electrons and six neutrons. Electrons Protons Neutrons

Carbon has six electrons, six protons and six neutrons. The Atom C - Carbon Carbon has six electrons, six protons and six neutrons. Electrons Protons Neutrons

The Atom N - Nitrogen Nitrogen has seven electrons, seven protons and seven neutrons. Electrons Protons Neutrons

The Atom O - Oxygen Oxygen has eight electrons, eight protons and eight neutrons. Electrons Protons Neutrons

The Atom Na - Sodium Sodium has eleven electrons, eleven protons and twelve neutrons. Electrons Protons Neutrons

How many protons, neutrons and electrons? 1 5 8 P = 5 N = 6 E = 5 P = 8 N = 8 E = 8 P = 1 N = 0 E = 1 H B O 1 11 16 92 11 17 P = 11 N = 12 E = 11 P = 92 N =146 E = 92 P = 17 N = 18 E = 17 Na Cl U 23 35 238

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This makes their MASS different. Isotope Atoms that have the same number of protons but different numbers of neutrons. This makes their MASS different.

Describe Isotope Example: http://education.jlab.org/glossary/isotope.html