The Periodic Table

1. The Periodic Table

2. The Periodic Table

3. Organization Dmitri Mendeleev, a Russian chemist, was the first publish a periodic table. He arranged the elements in rows by increasing atomic mass. To the left is an example of his periodic table. He realized that by putting the elements in this rows, characteristic traits created a pattern.

4. Mendeleev • Mendeleev was actually able to predict new elements from his arrangement of the periodic table. • He predicted that there would be an element with the atomic mass of 70 and he actually was only 2.6 off on his prediction for Germanium. • But he soon found out that all elements did not fit this arrangement.

5. Changes to the Table • It took 40 years after Mendeleev created the first table for a English chemist Henry Moseley to rearrange the periodic table by the atomic number instead of the atomic mass. • This allows for elements that have similar properties to appear at regular intervals.

6. Role of the Electron • The chemical properties of each group are largely determined by the number of valence electrons. • Since an element has the same valence electrons has another element in the same group, both will have similar physical and chemical properties.

7. Each row is called a “period” Periods • The elements in each period have the same number of shells 1st Period = 1 Shell 2nd Period = 2 Shells 3rd Period = 3 Shells 4th Period = 4 Shells www.chem4kids.com

8. Group 8 = 8 electrons Groups Group 1 = 1 electron Except for He, it has 2 electrons Group 2 = 2 electrons • Each column is called a “group” 3,4,5,6,7 • Each element in a group has the same number of electrons in their outer orbital, also known as “shells”. • The electrons in the outer shell are called “valence electrons” www.chem4kids.com

9. Transition Metals • Transition Metals have slightly different rules for shells and valence electrons. • This is something you will learn about in High School Chemistry. www.chem4kids.com

10. Ion Formation • To the Left of the Transition metals – All elements will form positive ions. • To the Right of the Transition metals – All elements will from negative ions. (However, Group 14 can form both) • Ions are atoms that have gained or lost electrons, the atom no longer has an equal number of electrons and protons.

11. Classification • Metals – Shiny solids that can be stretched and shaped. They are good conductors of heat and electricity.

12. Classification • Nonmetals – except for hydrogen all of these are found on the right side of the periodic table. • Can be a solid, liquid, or gas at room temperature. • Solid nonmetals are often dull and brittle. • Not good conductor of heat and electricity. Can be used as insulators.

13. Classification • Semiconductors (Metalloids) – Share properties with metals and nonmetals • Conduct electricity under certain conditions • Also, the main components of chips in computers and in other electronic devices.

14. Families • Alkali Metals • Alkali-Earth Metals • Transition Metals • Halogens • Nobel Gases • Semiconductors

15. Alkali Metals • Group 1 • Soft, shiny, and reacts violently with water. • Usually stored in oil, so that they are not able to react with the moisture in the air. • VERY REACTIVE, because of the one valence electron • Will not be found naturally alone in nature. • Similar physical properties

16. Alkaline-Earth Metals • Group 2 • Harder, denser, stronger, and have higher melting points than alkali metals. • Two valence electrons, will form positive ions, for example, Ca2+. • Usually used to create the hard exterior of animal shells and for structures in a airplanes.

17. Transition Metals • Groups 3 -12 • Less reactive again, and can form positive ions. • The transition metals can form several possible ions, that is why we ignore them! • Harder, denser, and higher melting points than alkaline-earth metals. • Very useful metals in this classification.

18. Halogen • Group 17 • Seven valence electrons, only need one electron to become stable • Combine easily with alkali metals • Examples: Chlorine is swimming pools, Fluorine is a poisonous yellow gas, Bromine is a dark read liquid and Iodine is a dark purple solid.

19. Noble Gases • Group 18 • 8 valence electrons, stable, under normal conditions will not bond with other elements • Most common noble gases are helium (used in balloons) and argon (fill light bulbs). Neon Signs

20. Semiconductor • Or Metalloids • Mixed into the 13, 14, 15, 16 groups • Elements that are able to conduct heat and electricity under certain conditions. • Ex. Boron is added to steel to increase the hardness and strength because Boron is a hard element.

21. The End of the Unit! Study Game!