Chapter 5 The Periodic Table

Organizing the Elements Section 1 Organizing the Elements

Learning Targets I can explain how the periodic table was created I can differentiate between periods and groups

Elements Science has come along way since Aristotle’s theory of Air, Water, Fire, and Earth. Scientists have identified 90 naturally occurring elements, and the rest are man made.

Elements The elements, alone or in combinations, make up our bodies, our world, our sun, and in fact, the entire universe.

How were the elements first organized? 1869 Dmitri Mendeleev Published the first periodic table Arranged elements in rows by increasing atomic mass All the elements in a column had similar chemical properties

Why did Mendeleev leave gaps in the periodic table? He predicted that scientists would eventually find the elements that would fill those gaps.

What was the problem with Mendeleev’s periodic table? Some elements did not fit the pattern He had to reverse some of the elements so that they were in columns with similar elements but now they were not in increasing mass

Who is noted with changing the original periodic table? Henry Moseley Arranged by increasing atomic number atomictheorytimeline.blogspot.com

What is periodic law? The law that states that the repeating chemical and physical properties of elements change periodically with the atomic numbers of the elements

What can you tell me about the rows in a periodic table? Called periods 7 periods Determine the number of energy levels As you move from left to right: Elements become less metallic Reactivity and conductivity changes

What can you tell me about the columns in a periodic table? Called groups Elements in columns have similar chemical properties Why? Each column has the same number of valence electrons chem4kids.com modelscience.com

Learning Target Checkpoint Who created the first periodic table? How was it arranged? Who arranged the periodic table by increasing atomic number? Differentiate between periods and groups.