Organizing the Elements

1. Organizing the Elements Chapter 9 Lesson 1 Page 314

2. 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

3. 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

4. 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

5. 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?

7. 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 made of smaller particles)

8. 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

9. 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

10. Reading the Periodic Table • 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

11. Chemical Symbol of Potassium

12. 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

13. 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

14. 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

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