17.3 The periodic table

1. 17.3 The periodic table

2. Warm up • What is the atomic number and the atomic mass of Silicon? • Calculate the number of protons, electrons and neutrons in the following element if the atomic number is 28. • Is the atom of Si considered neutral? Why?

3. Objectives • Explain the composition of the periodic table. • Use the periodic table to obtain information. • Explain and distinguish between metals, non – metals and metalloids.

4. Introduction • Complete the following patterns:

5. Each month, the moon seems to look at one of the following phases: This type of change is periodic “ repeated in a pattern”

6. Organizing of the element • In the late 1800, Dmitri Mendeleev searched for a way to organize elements. • When he arranged all the elements known at that time in order of increasing atomic mass, he discovered a pattern. • Chemical properties in light elements were repeated in heavier elements. Because the pattern repeated, it is now considered to be periodic.

7. Organizing of the element • Later, Henri Moseley established that each elements has a unique atomic number, which is how the current periodic table is organized. • Today the arrangement of the elements is called the periodic table of elements. • In the periodic table, nowadays, elements are arranged according to the increasing atomic number and by changes in physical and chemical properties.

8. Current periodic table • The modern periodic table uses Moseley’s arrangement of elements.

9. The periodic law • The periodic law states that when the elements are arranged by increasing the atomic number, a periodic repetition of chemical and physical properties of the elements are noticed.

10. Sort or group the following objects according to their properties.

11. The atom and the periodic table • Elements in the periodic table are arranged in groups, or families, and are numbered from 1 through 18. • Elements in each group have similar properties. • Example: gold, silver and copper

12. If you looked at one atom of every element in a group you would see… • Each atom has the same number of electrons in it’s outermost shell. • An example… The group 2atoms all have 2 electrons in their outer shells Be (Beryllium) Atom Mg (Magnesium) Atom

13. Why do elements in the same group have similar properties? • Do you know where electrons are located? • Scientists have found that electrons within the electron cloud have different amount of energy. They placed electrons in energy levels around the nucleus. • The number of outer or “valence” electrons in an atom effects the way an atom bonds. • The way an atom bonds determines many properties of the element. • This is why elements within a group usually have similar properties.

14. Maximum number of electrons in an energy level is 2n2 where n is the number of energy levels

15. Application • How many electrons are found in: 1- first energy level 2- second energy level 3- third energy level 4- fourth energy level

16. Energy levels • The energy levels where electrons are distributed around the nucleus are named using numbers 1 to 7. • What is the maximum number of electrons in energy level: 1, 2, 3 & 4? • A complete and stable outer energy level can contain a maximum of 8 electrons

17. Rows on the table • Electrons are distributed in energy levels around the nucleus. • Elements are arranged in rows in the periodic table. • Each row of the periodic table specify the number of energy level an atom has. • The horizontal rows of the elements on the periodic table are called periods. • The element increase by one proton and one electron as you go from left to right in the periodic table

18. Which of the following has a stable outer energy level? Find the group and the period of each of the following element.

20. Electron dot diagram • Way to represents the number of electrons in the outer energy level. • Created by an American Chemist known as Lewis • Also known as Lewis dot symbol • Uses the symbol of the element and the valence electrons (electrons of the outermost energy level)

22. Application • Draw the Lewis dot diagram of the following elements: Carbon – sodium – sulfur – neon – hydrogen – calcium – magnesium – chlorine – oxygen – boron – beryllium – lithium – potassium – nitrogen – fluorine - phosphorous – silicon- Aluminum – helium and Argon

23. Same Group or same Period • Elements on the same group have the same number of electrons in the outermost energy level. • Since all members of a group on the peridic table have the same number of electrons in the outer energy level, group members will undergo chemical reactions in the same way. • Elements on the same period or row on the periodic table have the same number of energy levels. Example: (H & He), Li & Be & B & C & N & O & F & Ne)

24. Regions of the periodic table • The periodic Table is divided into several groups based on the properties of different atoms.

27. Wrap up • Use the periodic table to find the name, atomic number, symbols, the average atomic mass , group, and the period for the first 20 elements • Definethe periodic law • Compare and contrast the ways in which Mendeleev and Moseley classify the elements in the periodic table • Definegroups and periods • Draw electron dot diagrams • Describethe general characteristics of metals, nonmetals, and metalloids • Indicatethe energy levels where electrons are arranged. • the maximum number of electron that each energy level can hold (2n2), where n= number of energy level( n=1,2.3…., n=7)

28. Assignments • Home work section review questions page: 524 • Quiz 2 in section 17.1: Structure of the atom 17.2: Masses of the atom 9-08 on Wednesday, feb. 15, 2012 9-05, 9-06 & 9-07 on Thursday, Feb. 16, 2012