The table we made as a class during the exploration : This table represents the largest number of trends using the given elements.

Dmitri Ivanovich Mendeleev and The Periodic Table The Past, Present, and Future

Review 0 Atomic Number (Z): The number of protons in the nucleus of an atom. Represented by whole numbers. Atomic Mass: The average mass of an atom of an element. 1 H Reactivity: A property that describes whether an element or compound will chemically combine with other substances to form compounds and also describes the speed of a reaction.

Introduction 0 Who is Mendeleev, and what did he do? 0 Mendeleev’s Table of Elements and its Trends 0 The Modern Periodic Table and its Trends 0 The Similarities and Differences Between these Two Tables

Dmitri Mendeleev ( ) 0 Born in Verhnie Aremzyani village, near Tobolsk in Serbia.Tobolsk 0 He was a Russian Chemist 0 He is considered the father of the modern periodic table. 0 What did he know at the time? 0 Atomic Mass of Elements 0 Reactivity/ Properties of Elements mitri_Mendeleev

Mendeleev’s Table of Elements 0 At the time of Mendeleev, only 63 elements were known. 0 The Atomic Weights of Each (Some turned out to be wrong) 0 The Properties of Each 0 Used this knowledge to create a table of elements 0 On Feb 17, 1869, Mendeleev Published “An Attempt at a System of Elements, Based on Their Atomic Weight” 0 This is his first draft. Many revisions followed.

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The Trends And Missing Links 0 Trends that can be seen on Mendeleev’s table (Look at Handout: Mendeleev’s Table Flipped 90 degrees) : 0 Increasing Atomic Weight 0 Properties of the Elements 0 What is missing? 0 Elements with Question Marks 0 Not sure about the placement 0 Atomic Weights with Question Marks 0 Predicted Elements that had this atomic weight

The Modern Periodic Table of Elements

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The Trends 0 Increasing Atomic Number (Periodic Law) 0 When elements are arranged in order of increasing atomic number, there is a periodic repetition of their physical and chemical properties. 0 Increasing Atomic Weight 0 Properties (Metals, Metalloids, and Nonmetals) 0 Reactivity 0 There are columns called groups that are represented by a number that increases from left to right on table. 0 There are rows call periods that increase top to bottom on the table. 0 Could there be missing elements that we have not yet discovered? stock-photography-question-mark-thinker- image

Compare and Contrast 0 How does Mendeleev’s table of elements compare to the modern table of elements? (Look at Handouts) 0 Similarities: 0 Increasing Atomic Weight in Both (For the Majority of the table: Some exceptions (Example: Te(127.6) and I(126.9)) 0 The column in Mendeleev’s table are similar to the rows in the modern table. 0 Differences: 0 There are more elements known today that are on the modern table. 0 Some of the element names and atomic weights have changed a little (More accurate measurements can be made now.) 0 The arrangement of the columns and rows are different