![]() ![]() Rows & Columns CombinedOVERALL (back of PT) Determine which 2 elements will have properties most similar to Ca. Decide which 2 elements will have properties similar to those of Cl. 16 Locate the element Chlorine on your PT. Atomic mass (# of protons & neutrons) increases from left to right across a period.Atomic # (# of protons) from L to R across a period.Draw the number of shells for Periods 1 thru 7 on your PT.Write the val e-s for families I thru VIII on your PT.Elements in a period are not alike in properties.The horizontal rows of the periodic table are called periods (from repeating pattern).Li, Na, and K have similar properties, all in 1 group. Sodium (Na) has properties similar to Lithium (Li). Elementsin the same group or familyhave similar characteristics or properties.Ex.Metallic character increases from top to bottom.The vertical (up and down) columns of the periodic table (there are 18) are called groups (18)or families(I- VIII).Draw atomic structure of H & He as a class.Mass # is the # of protons PLUS the # of neutrons (each equals 1 AMU).Atomic # is equal to the number of protons or electrons (unless charged).What’s the difference between Mass # & atomic #? Atomic mass (round off for mass # p’s + n’s).Atomic # increasing by 1 means it has one more proton than the previous atom.Atomic # increases by 1, so it has 1 more valence electron than the previous family.The table works because it is based on the structure of atoms, especially the valence e-s (outermost shell).Across a row or down a column the elements’ properties change in a predictable way.An element’s properties can be predicted from its location on the table.Elements are now arranged by increasing atomic number.Published his table in 1869 the newelements were discovered within 16 years.He even predicted the properties of new elements.Mendeleev predicted that the blank spaces would be filled by elements that had not yet been discovered.So he moved the cards into the group it best fit. ![]() However, this did not always produce similar groups.Patterns appeared when elements were arranged in order of increasing atomic mass.He listed the elements’ known properties.To help him find a pattern he put all of the known information on individual cards.discovered a system for organizing all of the known elements.1860’s a Russian Scientist named Dmitri Mendeleev. ![]()
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