Exploring the Periodic Table: Mendeleev's Discovery and Elemental Patterns

1. Ch 10 The Periodic Table

2. 10.1 Using the Periodic Table Discovering a Pattern • Dmitri Mendeleev discovered a pattern to the elements in 1896. • First he wrote the names and properties of the elements on cards. • Then he arranged his cards in order of increasing mass. A pattern appeared!  • Periodic -happening at regular intervals • like days of the week.

3. 10.1 Using the Periodic Table Elements with similar properties occurred in a repeating pattern.

4. 10.1 Using the Periodic Table Discovering a Pattern • Mendeleev predicted that elements yet to be found would fill in the gaps in his table. • He was right! Missing element Germanium (Ge) fit into his gap.

5. 10.1 Using the Periodic Table Changing the Arrangement • Some elements did not fit in the table by increasing atomic mass – so Mendeleev changed his table. • 1914 Henry Moseley determined the number of protons in an element. When the periodic table was arranged by increasing atomic number, all elements fit the table. • Periodic Law-states that the repeating chemical and physical properties of elements change periodically with the atomic numbers of the elements

6. 10.1 Using the Periodic Table Decoding the Periodic Table • Each square on the periodic table includes: • Atomic number • Chemical symbol • Chemical name • atomic mass

7. 10.1 Using the Periodic Table Decoding the Periodic Table • Period- Each horizontal row of elements • Group- Each column of elements. • Elements in the same group have similarproperties. • Elements in the same period have the same number of electron shells

8. 10.2 Metals • The Periodic Table and Classes of Elements • We break elements into three major groups • Metals • Nonmetals • Metalloids

9. 10.2 Metals • Metals– found to the left of the zigzag line • Few electrons in the outer energy level • All solids at room temp. except Mercury (Hg) • Lustrous • ductile • malleable • good conductors

10. 10.2 Metals • Properties of metals • Luster - describes the ability of a metal to reflect light • Malleability - describes the ability of a substance to be hammered or rolled into sheets • Ductility- describes the ability of a substance to be pulled into thin wires • Good conductors of electricity and thermal energy • Higher densities, boiling points, and melting points in general

11. 10.2 Metals • Alkali Metals • Group: 1 • Valence Electrons: 1 • Valence electron - electron in the highest occupied energy level • Reactivity : Very reactive • can easily give away the 1 electron • Often stored in oil because they react violently with water and oxygen • Soft, silver color, shiny and low density

12. 10.2 Metals Alkali metals in water

13. 10.2 Metals • Alkaline Earth Metals • Group: 2 • Valence Electrons: 2 • Reactivity: reactive but less than alkali metals • silver color, higher density

14. 10.2 Metals Chlorophyll contains Mg; oyster shell, pearl, and cast contain calcium

15. 10.2 Metals • Transition Metals • Group: 3-12 • Valence Electrons: varies (1 or 2) • Reactivity: much less reactive • Shiny, good conductors, higher densities and melting points (except Hg) • Some transition metals from periods 6 & 7 appear below the table to save space. • Elements in each row tend to have similar properties • Lanthanides- shiny, reactive metals • Actinides- radioactive , or unstable. Elements listed after plutonium do not occur naturally.

16. 10.3 Nonmetals and metalloids • Nonmetals- found to the right of the zigzag line • almost a complete outer energy level (Group 18 is complete) • more than half are gases at room temp. • not shiny • not malleable • not ductile • not good conductors (good insulators)

17. 10.3 Nonmetals and metalloids • Metalloids– found on the zigzag • outer energy level is half full • have some properties of metals • have some properties of nonmetals • sometimes called semiconductors • Semiconductors conduct electricity at high temperatures but not at low temperatures

18. 10.3 Nonmetals and metalloids • Boron Group • Group: 13 • Valence Electrons: 3 • Reactivity: reactive • 4 metals, 1 metalloid • solid at room temp. • Aluminum (Al) is most abundant metal in Earth’s crust

19. 10.3 Nonmetals and metalloids

20. 10.3 Nonmetals and metalloids • Carbon Group • Group: 14 • Valence Electrons: 4 • Reactivity: varies • solids at room temp. • carbon is nature’s most important element. Found in carbohydrates, proteins, fats, and nucleic acid (DNA) • Germanium and silicon are used as conductors in computer chips

21. 10.3 Nonmetals and metalloids

22. 10.3 Nonmetals and metalloids • Nitrogen Group • Group: 15 • Valence Electrons: 5 • Reactivity: varies • most are solids at room temp. except N • N is 80% of the air we breathe, fertilizer

23. 10.3 Nonmetals and metalloids

24. 10.3 Nonmetals and metalloids • Oxygen Group • Group: 16 • Valence Electrons: 6 • Reactivity: very reactive • Oxygen (O) is 20% air and needed for substances to burn

25. 10.3 Nonmetals and metalloids

26. 10.3 Nonmetals and metalloids • Halogens • Group: 17 • Valence electrons: 7 • Reactivity: very reactive – most reactive nonmetals • Form salts with alkali metals • poor conductors

27. 10.3 Nonmetals and metalloids

28. 10.3 Nonmetals and metalloids • Noble Gases • Group: 18 • Valence electrons: 8 (except He – 2) • Reactivity: unreactive • Colorless, odorless gases at room temp.

29. 10.3 Nonmetals and metalloids

30. 10.3 Nonmetals and metalloids • Hydrogen • Group: 1 - in group 1 only due to valence electrons • (does not share any other properties with the alkali metals) • Valence electrons: 1 • Reactivity: very reactive • colorless, odorless, explosive reactions w/ oxygen