**"Evolution of the Periodic Table: From Newland to Moseley"**

1. Chapter 4Section 1

2. John Newland • 1865 he arranged the 1st 16 elements • Ordered them by increasing atomic mass • He found that elements in each column had similar chemical and physical properties • The properties repeated with the 8th element

3. Dmitri Mendeleev • Arranged the 63 known elements in 1870 • Arranged them in order of increasing atomic mass • Elements with similar properties fell in vertical columns

4. Dmitri Mendeleev • Two interesting things to notice about Mendeleev’s table • The elements do not always fit neatly in the order of increasing atomic mass • There were gaps in the table where elements with a particular atomic mass should occur

5. Henry Moseley • 40 years later Moseley studied the X-ray spectra of the elements and found that they correlate to the atomic number • Arranging the elements in order of increasing atomic number caused the discrepancies to disappear

6. Periodic Table • The periodic table on page 114-115 is the most common periodic table • It is based on periodic law • Periodic law: • Physical and chemical properties of the elements are a periodic functions of their atomic numbers

7. Periodic Table • Rows = Periods • Electron Configurations are similar • Columns = Groups • Have properties in common with gradation • Period: Series of elements that form a horizontal row in the periodic table • Group: Series of elements that form a vertical row in the periodic table

8. Periodic Table • 2 distinct regions • Metals – Groups 1-12 and some elements in 13-16 • Nonmetals – Groups 17 and 18 as well as some in Groups 14-16 • Transition metals – Groups 3-12

9. Main-Group Elements • What are the main-group elements in the periodic table? • Groups 1,2 and 13-18 • Names for the main-group elements: • Group 1: Alkali metals • Group 2: Alkaline-earth metals • Group 17: Halogens • Group 18: Noble Gases

10. Alkali Metals • React with water to produce alkaline solutions • Soft and can be cut with a knife • Have a high reactivity due to their electron configuration • Single electron in the highest energy level • Lose the outer electron and become a cation (+)

11. Alkaline-Earth Metals • Harder, denser, stronger and have higher melting points than Group 1 • Elements reactive but less than Group 1 • Requires twice as much energy • Lose 2 electrons to achieve the configuration of a noble gas

12. Halogens • Combine with most metals to form compounds known as salts • Most reactive group of the nonmetals • 1 electron short of a noble gas configuration • Gain an electron and become an anion (-)

13. The Noble Gases • Have 8 electrons in the outermost energy level • Stable configuration • Low reactivity

14. Hydrogen • Most common element in the universe • Reacts with many elements • Used in industry to produce ammonia