3.3 The Atom and Electrons!

How do we know so much about atoms? Answer: Particle Accelerators Whether it is Rutherford and his gold foil, or the Large Hadron Collider. These accelerators help us “see” atoms. LHC – built from 1998 – 2008 in Geneva Switzerland

Large Hadron Collider and the Higgs Boson

Particles in an atom Small Smaller da Protons Neutrons Electrons Quarks Gluons Leptons Hadrons Bosons Fermions da

Atomic Structure: Electrons Electrons (e-’s) have a negative charge. Mass is roughly 1/2000 that of a proton or neutron and often referred to as 0 The mass of the electron is referred to as negligible.

Periodic Table of Elements Atomic Number: Number of protons in an atom; usually appears directly above the chemical symbol. Number of protons in an element is usually balanced by an equal number of electrons (negatively charged particles).

Atom Equations Atomic Number = # of Protons = # of Electrons Mass Number = # of Protons + # of Neutrons # of Neutrons = Mass Number - # of Protons # of Protons = Mass Number - # of Neutrons

Ions Ions: Have the same atomic number and the same mass number, but have a different charge because of a different number of electrons Octet Rule: Atoms try to gain or lose electrons to gain a stable octet or 8 electrons in their outer most energy level 2 electrons go in the first energy level 8 electrons go in the 2nd energy level 8 electrons go in the 3rd energy level

Compounds Pure substances made up of two or more elements. Physical and chemical properties of elements change when they bond with others substances. Molecule: the smallest part of a compound that still has all of the properties of that compound.

Particle Charge Mass Location Inside the Nucleus Protons Positive (+) 1 amu Inside the Nucleus Neutrons No Charge 1 amu Outside the Nucleus Electrons Negative ( - ) Negligible

Atomic Structure: Electrons