We can categorize the elements into…. Metals. Metalloids. Nonmetals. Metals. Properties of Metals. Metals are good conductors of heat and electricity. Metals are shiny. Metals are ductile (can be stretched into thin wires). Metals are malleable (can be pounded into thin sheets).
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We can categorize the elements into…. Metals. Metalloids.Nonmetals.
Properties of Metals • Metals are good conductors of heat and electricity. • Metals are shiny. • Metals are ductile (can be stretched into thin wires). • Metals are malleable (can be pounded into thin sheets). • A chemical property of metal is its reaction with water which results in corrosion.
Properties of Metalloids Silicon • Metalloids (metal-like) have properties of both metals and non-metals. • They are solids that can be shiny or dull. • They conduct heat and electricity better than non-metals but not as well as metals. • They are ductile and malleable. • Fall along the stair-step line on table • B, Si, Ge, As, Sb, Te, Po
Properties of Non-Metals • Non-metals are poor conductors of heat and electricity. • Non-metals are not ductile or malleable. • Solid non-metals are brittle and break easily. • They are dull. • Many non-metals are gases. Sulfur
http://www.lyon.edu/webdata/Users/DMcDowell/GenChem/alkalishow.htmlhttp://www.lyon.edu/webdata/Users/DMcDowell/GenChem/alkalishow.html Alkali Metals Soft, silvery colored metals Very reactive!!!
Alkali Metals reacting with water: • Li (Lithium) • Na (Sodium) • K (Potassium) • Rb (Rubidium) • Cs (Cesium)
Alkaline Earth Metals Silvery-White Metals Fairly reactive Many are found in rocks in the earth’s crust
Transition Metals Most are: Conductors of electricity and heat Malleable and Ductile (easily hammered into sheets or made into wires)
Nonmetals Brittle Do not conduct electricity
Halogens Most are Poisonous Fairly reactive
Noble Gases Unreactive Gases at room temperature
What about Hydrogen?? • The hydrogen square sits atop Family AI, but it is not a member of that family. Hydrogen is in a class of its own. • It’s a gas at room temperature. • It has one proton and one electron in its one and only energy level. • Hydrogen only needs 2 electrons to fill up its valence shell.
Vertically into Groups (1 – 18) Horizontally Into Periods (1-7) Elements are arranged:
Periods ** This is what the full periodic table looks like, the Lanthanide and Actinide are only moved down so it will fit on a sheet of paper!**
Periods vs Groups Periods/Rows Groups/Families/Columns Vertical Columns (1-18) Tends to have the same physical and chemical properties • Horizontal Row (1-7) • Corresponds to energy levels
If you looked at an atom from each element in a period you would see…
The period 4 atoms each have 4 electroncontaining shells 4th Shell K (Potassium) Atom Kr (Krypton) Atom Fe (Iron) Atom
Each atom has the same number of electrons in it’s outermost shell. • An example…
The group 2 atoms all have 2 electrons in their outer shells Be (Beryllium) Atom Mg (Magnesium) Atom
The number of outer or “valence” electrons in an atom effects the way an atom bonds. • The way an atom bonds determines many properties of the element. • This is why elements within a group usually have similar properties.
Each group/column/family has distinct properties • The periodic Table is divided into several groups based on the properties of different atoms.
History of the Atomic Theory • Atom – smallest particle of matter which will exhibit the properties of that element • Atoms are typically 0.00000008 cm • Models are used to describe what they understand about the atomic theory, many have been proposed and we study only a few
1803 • John Dalton • Father of the Modern Atomic Theory • Proposes his theory, based on scientific research
Postulate #1 • Elements are composed of atoms, which are very small, indivisible, indestructible particles. • True or Wrong?
Wrong ……we know about subatomic particles.
Postulate #2 • All atoms are of the same element are identical. • True or Wrong??
Wrong ….they aren’t exactly the same because of isotopes (atoms with same number of protons but different number of neutrons).
Postulate #3 • Atoms of different elements have different properties. • True or Wrong??
Postulate #4 • Atoms combine in small, whole-number ratios to form compounds. • True or Wrong??
Postulate #5 • Atoms of one element cannot change into an atom of a different element during a chemical reaction. • True or Wrong??
1897 JJ Thompson Electrons discovered by experiments with cathode ray tubes + magnetic field - Magnetic field Electron stream w/o applied magnetic field Electron stream after applied magnetic field **He was finally able to show that the beam could be deflected by an electric field, and thus consisted of NEGATIVELY CHARGED PARTICLES (AKA ELECTRONS)
1904 • JJ Thompson again… • Published atomic theory that’s now known as Plum Pudding Model • Thought electrons moved randomly in a positively charged, amorphous “pudding” or cloud
1909 • Rutherford • Gold Foil Experiment • Proved the existence of the atomic nucleus
The alpha particles were huge compared to electrons. If the Plum Pudding Model was correct, what should the results of the experiment be? If the Plum Pudding Model was correct, all of the alpha particles should go through the gold foil with little or no deflection.
1911 • Rutherford • Publishes new version of the atomic theory • Rutherford’s Atomic Theory: • The atom has a dense, positively charged core (aka nucleus) which contains most of the mass. Most of the atom is empty space. The electrons are somehow moving around the empty space.
1915 Negative electron • Niels Bohr proposes the Bohr Model, also called the Planetary model • This states the electrons orbit the nucleus much like planets around the sun Nucleus (positively charged)