Intro to the periodic table Unit 5

Mendeleev and the first periodic table  Middle of the 19 th century,  Dmitri Mendeleev organized the known elements their atomic masses

Mendeleev’s first sketch of the periodic table and the first published periodic table (1869)

 Did you notice there are some blanks on Mendeleev’s first periodic table???  He was so confident that his organization of elements showed repeating properties that He was able to predict undiscovered elements!!

Two problems with the first P table  1. Why could most of the elements be arranged in order of increasing mass but a few could not?  2. What was the reason for chemical periodicity (why did properties repeat)?

The Answer  40 years later  Henry Moseley organized the periodic table by atomic number (number of protons)  Elements fit into groups better

The Modern Periodic table  Is organized in order of increasing atomic number

Modern Periodic law  The discovery and use of atomic numbers to organize the p. table led to the Periodic law : Properties of elements repeat periodically when elements are arranged by atomic number

Groups And periods -groups/families: vertical columns, have similar properties -periods: horizontal rows

Representative Elements  All of the elements found in group 1,2, are called the representative elements.  Why?  Represent all 3 types of elements, metals, nonmetals and metalloids

Representative Elements

Types of Elements  Metals A metal is an element that is a good conductor TO THE LEFT OF STARICASE Some properties of metals most are solids at room temperature Malleable ductile conduct electricity and heat well

Metals: gold, copper, aluminum

Types of Elements  Nonmetals A nonmetal is an element that is a poor conductor TO RIGHT OF STAIRCASE Some properties of nonmetals many are gases solids are brittle poor conductors of heat and electricity

Nonmetals: carbon, sulfur, phosphorous, iodine

Metalloids  Metalloids A metalloid is an element that has characteristics of both metals and nonmetals Properties of metalloids all metalloids are solids at room temperature semiconductors of electricity

Metalloids

 Check your understanding: Would most elements on the periodic table be metals, nonmetals, or metalloids?

The s block  Group 1 A:, alkali metals (not H)  MOST reactive metals  React with water Group 2 A, alkaline earth metals harder and denser that group 1 not as reactive as group 1, but still very reactive

The d block  Groups 3-12: Transition metals  Typically less reactive than groups 1-2 so can be found as free elements in nature  aka: Group B

The halogens  Group 17  The most reactive nonmetals

The noble gases  Group 18: All gases  Inert (meaning unreactive; don’t form compounds because they already have all the electrons they need)

The bottom block  Every wonder why there are two rows of elements below the periodic table?  Inner Transition Metals, they would mess up trends if they were actually in the table so we pull them out!  Lanthanide series (top row)  Actinide series (bottom row)

 The lanthanides  Between group 3 and 4 in the 6 th period  Similar in reactivity to alkaline earth metals  Fun Fact: Lutetium has almost no applications. As a result it used to be the most expensive element in the world. These days it is easily available as a side product of other lanthanide production and its price has fallen.

 The actinides  Between group 3 and 4 in the 7 th period  All radioactive; all above Np are man made  Fun Fact: A radioactive button like this is inside most smoke detectors. A trace of americium creates charged particles that betray the smoke. Americium is thus the only man-made element available in grocery stores.