Chapter 12

1. Chapter 12 The Periodic Table

2. Section 1: Objectives • Describe how Mendeleev arranged elements in the first periodic table. • Explain how elements are arranged in the modern periodic table. • Compare metals, non-metals, and metalloids based on their properties and on their location in the periodic table. • Describe the difference between a period and a group.

3. How to Read the Periodic Table • Before we can sketch elements, we have to know how to read the periodic table. • Elements are divided into squares. • Each square tells you 5 things: • Element symbol • Atomic number • Element name • Atomic mass (mass number) • Physical state of element (M, NM, Mt)

4. Discovering a Pattern • Before the 1860s, scientists had never arranged the elements. • In 1869, Russian chemist Dmitri Mendeleev arranged the elements inorder of increasing atomic mass. • These repeating patterns are periodic, meaning that they happen at regular intervals.

5. Discovering a Pattern • His pattern had gaps in it though. • He predicted that elements that had not been discovered would fill these gaps. • By 1886, all the gaps had been filled and his predictions were right.

6. Discovering a Pattern • A few elements did not fit the pattern. • In 1914, British scientists Henry Moseley found the number of protons in an atom. • When the elements were arranged by atomic number, they fit the pattern.

7. Discovering a Pattern

8. Discovering a Pattern • Elements are classified as metals, nonmetals, or metalloids. • Valence electrons (number of electrons in outer shell)helps determine an element’s properties. • The zigzag line on the periodic table helps you determine this.

9. Discovering a Pattern • Metals are found to the left of the zigzag line. • Atoms of most metals have few electrons in their outer shell. • Most metals are: • Shiny • Malleable • Good conductors of heat/electricity

10. Discovering a Pattern • Nonmetalsare found to the right of the zigzag line. • Almost all nonmetals have a complete set of electrons in their outer shell. • Nonmetals are: (the opposite of metals) • Not shiny • Not ductile • Not malleable • Poor conductors of heat/electricity

11. Discovering a Pattern • Metalloids are elements that border the zigzag line. • Atoms of metalloids have about half the number of electrons in their outer shell. • Metalloids have some properties of metals and some of nonmetals. • Metalloids are also called semiconductors. (Si)

12. Discovering a Pattern • Each square on the periodic table includes an element’s name, chemical symbol, atomic number, and atomic mass. • For most elements, the chemical symbol have one or 2 letters. • Why would some elements have 3 letters?

13. Discovering a Pattern • Each horizontal row of elements is called a period. • The chemical and physical properties of elements in a row follow a repeating pattern. • Each vertical column of elements is called a group. • Elements in the same group often have similar chemical and physical properties.

14. Discovering a Pattern • Elements in a group have the same number of valence electrons. • Atoms can give, take, or share electrons with other atoms. • An atom’s goal is to complete the outer energy level.

15. Section 1: Review Questions • 1)What is Mendeleev famous for? • 2) What did he predict about the periodic table? • 3) What did Moseley discover? • 4) What are valence electrons? • 5) List 2 properties of metals and nonmetals. • 6) What are metalloids also called? • 7)What does each square on the periodic table include?

16. Electron Cloud Rules • For today, there are 2 rules to know before adding electrons to a sketch: • Electron number will equal proton number. • The first level can hold only 2 electrons.

17. Identifying and Sketching Atoms • Directions: Draw each element square along with all information for that element. • Under the square write the number of protons, neutrons, and electrons. • Next sketch your element including all protons, neutrons, and electrons.

18. Identifying and Sketching Atoms • 1) Hydrogen (1 V.E.) • 2) Beryllium (2 V.E.) • 3) Boron (3 V.E.) • 4) Nitrogen (5 V.E.) • 5) Oxygen (6 V.E.) • 6) Fluorine ( 7 V.E.) • 7) Helium (2 V.E.)

19. Section 2: Objectives • Explain why elements in a group often have similar properties. • Describe the properties of the elements in the groups of the periodic table.

20. Group 1: Alkali Metals • Contain 1 valence electron. • Share physical and chemical properties. • Most reactive metals. • Can easily give away one outer level electron. • Alkali metals are so reactive, in nature they are only found combined with other elements. • Examples: • (Li) • (K)

21. Group 2: Alkaline-Earth Metals • Contain 2 valence electrons. • Less reactive than alkali metals. • It uses more energy for elements to give 2 outer shell electrons than to give one. • Examples: • (Be) • (Mg)

22. Groups 3-12: Transition Metals • Either 1 or 2 valence electrons. • Do not give away electrons as easily as elements in Groups 1 and 2. • Less reactive than Groups 1 and 2. • Share all properties of metals, but other properties vary widely. • Some transition metals appear at the bottom of the periodic table: • Lanthanides • Actinides

23. Lanthanides • Shiny • Reactive • Metals • Some of these elements are used to make steel.

24. Actinides • Radioactive (unstable) • The atoms of a radioactive element can change into atoms of another element. • Elements after Plutonium (94) on the periodic table are only man-made in laboratories.

25. Group 13: Boron Group • Contain 3 valence electrons. • Solid at room temperature. • Reactive • Contains all metals and 1 metalloid (Boron) • Examples: • (Al) • (Ga)

26. Group 14: Carbon Group • Contains 4 valence electrons. • Solid at room temperature. • The reactivity varies among the elements. • Contains one nonmetal, 2 metalloids, and 2 metals • Examples: • (C) • (Si)

27. Group 15: Nitrogen Group • Contains 5 valence electrons. • Solid at room temperature (except for nitrogen). • The reactivity varies among elements. • Examples: • (N) • (P)

28. Group 16: Oxygen Group • Contains 6 valence electrons. • All but oxygen are solid at room temperature. • Reactive. • Examples: • (O) • (S)

29. Group 17: Halogens • Contains 7 valence electrons. • Poor conductors of electric current. • Causes violent reactions with alkali metals. • Very reactive. • Examples: • (Br) • (F)

30. Group 18: Noble Gases • Contain 8 valence electrons. (except helium) • Colorless, odorless gases at room temperature. • Unreactive because their outer shell is full. (do not need to gain or lose electrons) • Examples: • (Ne) • (Ar) • (Rn)

31. Hydrogen • Contains 1 valence electron. • Reactive. • Colorless, odorless gas at room temperature. • Low density. • Explosive reactions with oxygen. • The properties of hydrogen do not match the properties of any single group, so it is set apart from other elements on the periodic table.

32. Chapter 12 Review Questions • What are group 13 elements called? • How many valence electrons does the carbon group contain? • List 3 properties of lanthanides. • _____ found the # of protons in an atom. • ____ _____ are outer shell electrons • Name the 2 most reactive groups.

33. Chapter 12 Review Questions • List the Group #, V.E. #, Group Name, and Element Symbol: • Nitrogen • Phosphorous • Radon • Francium • Rhodium • Cobalt • Lead • Bismuth • Indium • Bromine