Group 2: Many Electron Atoms, Periodic Table of the Elements, and Periodic Properties II. Periodic Table
- The periodic table was originally constructed to represent the patterns observed in the chemical properties of the elements.
- Chemists who attempted to explain patterns:
1. Johann Dobereiner- triads (i.e. chlorine, bromine, iodine)
2. John Newlands- octaves, idea that certain properties seemed to repeat for every eighth element
3. Dimitri Ivanovich Mendeleev- developed the current periodic table
- Grouped the elements on the basis of similarities in their chemical properties
- Left blank spaces at appropriate places where additional elements would occur
- Questioned values of atomic weights when they disagreed with the pattern of elements (changed beryllium, indium, and uranium)
- The periodic table can correctly predict the existence and properties of still unknown elements.
A common and popular version of the periodic table (from http://www.chem.wisc.edu/areas/reich/handouts/periodic-table.GIF).
- Each group contains compounds with similar electron configurations; except hydrogen and helium.
- The periodic table is organized by atomic number, reading left to right-top to bottom.
- Groups are the columns across the top numbering 1-18 with elements of the same valance electron in the column
- Periods are the rows on the side numbering 1-7 with a row having a common set of quantum numbers.
- The periodic table is organized containing many trends which will later be explained.
- In the periodic table elements are grouped into eight classes according to their properties.
- Largest group of elements.
- Characterized with physical properties such as efficient conduction of heat and electricity, malleability, ductility, and a lustrous appearance.
- Tend to lose electrons to form positive ions.
1. Alkali Metals- group 1A
Are very active elements that readily form ions with a 1+ charge when they react with nonmetals.
2. Alkaline Earth Metals- group 2A
Form ions with a 2+ charge when they react with nonmetals.
3. Transition Metals- group 3B-2B
4. Lanthanide Series- usually subset below table
5. Actinide Series- usually subset below table underneath Lanthanide series
6. Other Metals.
- Smaller group of elements
- Resides in the upper right hand corner of the periodic table
- Nonmetals tend to gain electrons in reactions with metals to form negative ions
7. Halogens- group 7A
Form diatomic molecules and react with metals to form salts containing ions with a 1- charge.
8. Noble Gases- group 8A
Exist under normal conditions as monatomic (single atom) gases and have little chemical reactivity.
B. The Elemental Square
- The typical elemental square contains the element name, atomic weight, atomic symbol and the atomic number (Z).
a. Element- A substance that cannot be decomposed into a simpler substance by a chemical reaction. A substance composed of only one kind of atom.
b. Atomic Weight- The weighted average of the atomic masses of the different isotopes of an element. Sometimes known as the atomic mass units (amu).
c. Atomic Number (Z)- The number of protons in the nucleus of an atom.
d. Atomic Symbol- Abbreviations to the current element name or the exception of the original name in Latin (i.e. Ag, Fe, K, Au and Pb).
Elemental square for Carbon (from www.cartage.org.lb.../Elements.htm*)*
- Also visible on some periodic tables is the radioactive symbol. This occurs with all elements after element 83.
Radioactive symbol (from www.acsu.buffalo.edu/~btboeing/*).
Word document form of wiki: *Group 2 Ashley Vokral-periodic table.doc