Atomic Structure Models

The Ancient Model Greeks were first to consider the fundamental nature of matter. Cut something in half enough times eventually it becomes a single uncuttable piece. The ATOM (atomos = greek for “uncuttable”

JJ Thompson - The “Plum Pudding” model Positive charge sphere (the pudding) Studded with negative charge electrons (the raisins) Used Cathode Ray Tubes and measured deflection of particles

The Cathode Ray Tube Cathode Ray Tube

Ernest Rutherford Discovered the Nucleus! Alpha Particles shot at gold foil were expected to pass right through Instead a small percentage of them were deflected! This meant there had to be a concentration of mass at the center!

Rutherford

James Chadwick Discovered the Neutron! Beryllium was bombarded with radiation It emitted particles with NO charge (neutral)

The final piece of the atomic puzzle… but was it all assembled correctly? The Atom?

Today’s Quantum Model The electron “cloud” model Electrons do not “orbit” the nucleus like planets They have “regions of probability” This is where electrons are LIKELY to be found. They move too fast to observe continuously!

Grouping the Elements

Families on the Periodic Table Elements on the periodic table have been grouped into families based on their chemical properties. Each family has a specific name to differentiate it from the other families in the periodic table. Elements in each family react differently with other elements.

Basic classifications Metals – Shiny, silver/grey/whitish, good conductors, malleable, high melting points Nonmetals – Dull, low melting points, poor conductors, brittle, Metalloids – Not metals, but not nonmetals either… properties of both!

shells

ALKALI METALS Group 1 Hydrogen is not a member, it is a non-metal (but also a Metal) 1 electron in the outer shell Soft and silvery metals Very reactive, esp. with water Conduct electricity

ALKALINE EARTH METALS Group 2 2 electrons in the outer shell White and malleable Reactive, but less than Alkali metals Conduct electricity

TRANSITION METALS Groups in the middle Good conductors of heat and electricity. Some are used for jewelry. Can bond with many elements in a variety of shapes.

BORON FAMILY Group 3 3 electrons in the outer shell Most are metals Boron is a metalloid Aluminum is on the metal/non- metal border, but is NOT a metalloid!

CARBON FAMILY Group 4 4 electrons in the outer shell Contains metals, metalloids, and a non-metal Carbon (C) Si and Ge vital to the information age (computers)

NITROGEN FAMILY Group 5 5 electrons in the outer shell Easily share electrons to form compounds (N and P especially) Contains metals, metalloids, and non-metals

OXYGEN FAMILY Group 6 6 electrons in the outer shell Contains metals, metalloids, and non-metals Reactive

Halogens Group 7 All are non-metals (Astatine is a metalloid) One electron away from full outer shells! Very reactive are often bonded with elements from Group 1 Like NaCl (Table salt!)

Noble Gases Group 8 Exist as gases Non-metals Full Outer electron shells, they don’t want to share! Not reactive with other elements

Rare Earth Metals Many are Radioactive The rare earths are silver, silvery-white, or gray metals. Conduct electricity Large Nuclei!

Why not show it this way? What would be the difficulty with this?