ATOMIC STRUCTURE

Dalton’s Theory All matter is made up of tiny particles called atoms Atoms of the same element are identical in size, mass, properties Atoms cannot be subdivided, created or destroyed Atoms of different elements combine to form chemical compounds

How much of this is true? Some of Dalton’s Theory about the atom has been altered based on new information This gives us the …..

Modern Atomic Theory All matter is made up of atoms. Atoms of the same element are chemically similar Atoms of an element may not have the same mass (Isotopes) Atoms are not subdivided, created or destroyed in chemical reactions.

Isotopes Ions Atoms of the same element with different masses Protons are the same Neutrons differ Looks like: uranium-235 Or Have an unequal number of protons and electrons Have an overall positive or negative charge Ions

Atomic Number Mass Number It represents the # of protons It can also represent the # of electrons if the atom is neutral Mass Number Represents the # of protons + # of neutrons # of Neutrons = Mass Number – Atomic Number

Subatomic Particles Particle Location Charge Mass

Periodic Table 13 Al 26.98154

Periodic Table 19 K 39.0983

Nuclear Symbols Fe Al 27 13 57 26

Nuclear Symbols Cl Al 3+ 1- 27 13 35 17

Elements, Isotopes and Ions 127I 127I- 129I

Describing the Atom J.J. THOMPSON - Showed that atoms are made of particles CATHODE RAY TUBE \

Describing the Atom MILLIKAN Calculated the charge on a single electron

Rutherford Showed that atom had both + and - charges : Radiation and Magnets (p106)

Rutherford See p 95 GOLD FOIL EXPERIMENT Showed atom mostly empty space & its mass is contained in a very small area GOLD FOIL EXPERIMENT See p 95 C:\Documents and Settings\Teacher\Desktop\1Rutherford_Expt.avi

Gold Foil Experiment

Flame Test *Electrons exist in energy levels (or ‘shells’). *When exposed to an energy source, electrons may become ‘excited’ and jump to a higher energy level. *When the electron returns to its ‘ground state’ a photon of light is released. *The photon of light is always the same wavelength (and the same color) for each element.