# Organizing the Elements - PowerPoint PPT Presentation

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Organizing the Elements. Chapter 9 Lesson 1 Page 314. Mendeleev. Created the first version of the periodic table in 1869 Arranged them according to their atomic masses Total of 63 elements in 1869 He discovered a set of patterns that applied to the elements. Mendeleev.

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Organizing the Elements

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## Organizing the Elements

Chapter 9

Lesson 1

Page 314

### Mendeleev

• Created the first version of the periodic table in 1869

• Arranged them according to their atomic masses

• Total of 63 elements in 1869

• He discovered a set of patterns that applied to the elements

### Mendeleev

• He knew there were certain similarities and patterns to the elements, he also knew there was more than he had already discovered about them so he did more research

• He found: melting point, density, color, and atomic mass

• Atomic mass- the average mass of all the isotopes of the elements

• Isotopes- different forms of the same element

### Mendeleev

• Mendeleev noticed that a pattern of properties appeared when he arranged the elements in order of increasing atomic mass. He found that the properties repeated regularly.

• He put the elements with similar properties in groups

• Read last paragraph page 315

### Periodic Table

• Periodic table- an arrangement of elements showing the repeating pattern of their properties

• Mendeleev left blanks in his periodic table knowing that elements with the properties he predicted would later be discovered. He was right!

• Do we still do that?

### Periodic Table Info

• What information does the periodic table contain?

• The table is built based on atoms ( thought of as the smallest particles of

matter, until late 1800s when

we discovered they were

### Parts of the atom

• Nucleus- very center of the atom which contains protons and neutrons

• Protons- positively charged particles (every atom of the same element has the same # of protons)

• Atomic number- number of protons in an element used to identify elements

• Modern periodic tables are arranged in increasing atomic number rather than weight

### Parts of the atom

• Neutrons- particles that have no charge found in the nucleus (neutral)

• Protons and neutrons have about the same mass

• Electrons- negatively charged particles that move around the outside of the nucleus

• Neutral atoms has the same number of electrons and protons

• The periodic table includes, the atomic number, chemical symbol, name, and atomic mass for each element

• Look at page 319 to see the information that is found for each element in the book’s periodic table

### How is the Periodic Table used?

• As you look across the table, the elements’ properties change in predictable ways

• An element’s properties can be predicted from its location from its location in the periodic table

### Periods

• Period- the rows of the periodic table

• Metals are located on the left

• Non-metals on the right

• Metalloids are found in between

• This patter is repeated in each period

### Groups

• Modern table has 7 periods which forms 18 columns

• Groups- columns(aka families)

• Patter repeats in each period

• Characteristics are similar in each group

• Example: except for H, all elements in group 1 react violently with water

### Homework

• Figure out why the two rows at the bottom are separate from the rest of the table.