Periodic Table

1. Periodic Table

2. Patterns in Element Properties • Some elements exhibit similar chemical and physical properties. For example, lithium (Li), sodium (Na), and Potassium (K) can all combine in a 1:1 ratio easily with Chlorine.

3. Elements With Similar Properties • The elements chlorine, bromine, and iodine look very different from each other. But each forms a similar-looking while solid when it reacts with sodium.

4. John Newlands Noticed a Periodic Pattern • In 1865, an English chemist, John Newlands, arranged the known elements according to their properties and in order of increasing atomic mass. • He noticed that all of the elements in a given row had similar properties, and they repeated every 8 elements (he called this the law of octaves).

5. Newlands’ Table • In Newland’s time, determining atomic weights was based on comparing other elements to the lightest element (hydrogen). Some of the elements were given inaccurate values. . • Newland was ridiculed by other chemists who felt the table he created was not reliable. He could not get his papers published and returned as chief chemist in a sugar factory and later opened a chemical business with his brother.

6. Dmitri Mendeleev Invented the First Periodic Table • In 1869, a Russian chemist, Dmitri Mendeleev produced the first orderly arrangement (periodic table) of all 63 elements known at the time.

7. Mendeleev—the Father ofthe Periodic Table • Mendeleev (1834-1907) rose from very poor beginnings to a position of a renowned Russian chemist in the 19th century. He wrote down information on each element on cards. He ranked the elements from lightest to heaviest. • Mendeleev also put the elements into a table according to their properties. He started a new row each time he noticed that the chemical properties of the elements repeated.

8. Mendeleev Correctly Predicted the Gaps • Mendeleev’s Table contains gaps that elements with particular properties should fill. • He correctly predicted the properties of the missing elements. He even gave them provisional names. These elements were eventually discovered.

9. Henry Moseley • A young English chemist, Henry Moseley, discovered that the elements should be organized according to their atomic numbers, not their atomic weights as was done before. • When Moseley studied the lines in the X-ray spectra of 38 different elements, he found that the wavelength of the lines decreased in a regular manner as atomic number increased.

10. Henry Moseley • Henry Moseley lost his life in 1915 during World War I at the Gallipoli battle in Turkey at the age of 27 and is buried there. His death has been called one of the greatest tragedies of WWI because he was such a brilliant chemist.

11. The Periodic Law • The Periodic Law states that when the elements are arranged according to their atomic numbers, elements with similar properties appear at regular intervals.

12. Organization of the Periodic Table • Elements in each column of the table have the same number of electrons in their outer energy level. • These electrons are called valence electrons.

13. Valence Electrons • The outer energy level electrons in an atom are the ones that participate in chemical reactions with other atoms. • Elements with the same number of valence electrons react in similar ways.

14. Groups • A vertical column on the periodic table is called a group. (These are also called families.) These exhibit similar properties.

15. Relationship between Groups and Electron Configuration: • The group an element belongs to is determined by the last notation in its’ electron configuration. • For example, all elements that end in s1 have the same properties and are in the same group.

16. Periods • A horizontal row on the periodic table is called a period. Elements in the same period have the same number of occupied energy levels.

17. Blocks of Elements • The Periodic Table is organized into blocks—each corresponding to the sublevels. (S, P, D, and F)