2018 SSNI Atomic Fundamentals Marissa Reigel A discussion and activities about the building blocks of matter.

Matter Term that describes all of the physical substances around us your table your body your pen or pencil Everything! Anything that has mass and takes up space (has volume) Matter is made up of different kinds of atoms

Models… In the case of atoms, scientists use large models to explain something that is very small Models of the atom are used to explain data or facts that were gathered experimentally Models are theories Often used for things that are too small to be observed large to be observed difficult to be understood easily

Early Models of the Atom… John Dalton All elements are composed of indivisible particles (atoms) Atoms of the same element are the same Atoms of different elements are different Compounds consisted of atoms of different elements combined together Element A atom Element B atom Element C atom Compound with elements A, B, & C

Early Models of the Atom… JJ Thomson Plum pudding model Atom is Made of a positively charged material (pudding or soup) With the negatively charged electrons scattered through it

Early Models of the Atom… Ernst Rutherford Mostly empty space Small, positive nucleus Contained protons Negative electrons scattered around the outside (“cloud”) Planetary model

Early Models of the Atom… P E Niels Bohr Electrons have certain classical motions Electrons orbit around the nucleus at discrete distances (shell structure) Nucleus (sun) is composed of protons and neutrons Attraction due to electrostatic forces

Atomic Structure Nucleus Protons Neutrons Electrons Space

Atomic Structure If an atom could be enlarged to the size of a football stadium… The nucleus (protons and neutrons) would be the size of a grape or a marble at midfield Orbiting electrons would be size of salt grains swirling around the upper deck

Atomic Structure – Bohr’s model based on results of Gold Foil Experiment

Atomic Structure – Bohr’s model based on results of Gold Foil Experiment (Zinc Sulphide)

Activity: What’s Inside the Atom? Roll marble Determine the geometric shape underneath

Atomic Structure… Electrons Tiny, very light particles (negligible mass) Have a negative electrical charge (-) Move around the outside of the nucleus

Atomic Structure… Protons Number of protons = atomic number Much larger and heavier than electrons Have a mass of 1 AMU Protons have a positive charge (+) Located in the nucleus of the atom Atoms with same number of protons are the same element Number of protons = atomic number

Atomic Structure… Neutrons Large and heavy like protons Have a mass of 1 AMU Neutrons have no electrical charge Located in the nucleus of the atom Neutralize repulsive force of positive protons Acts as a “glue” that keeps protons in the nucleus Number of protons + number of neutrons = atomic mass