Elements and the Periodic Table

1. Elements and the Periodic Table A Brief History….

2. Plumbum Natrium Aurum Argentum Hydrargyrum Kalium Ferrum Ancient Names for the elements

3. Proposed in 1803: (1) all matter was composed of small indivisible particles termed atoms, (2) atoms of a given element possess unique characteristics and weight (3) three types of atoms exist: simple (elements), compound (simple molecules), and complex (complex molecules). John Dalton - Atomic Theory

5. Symbols for the elements used by Dalton

6. Dalton’s Symbols

7. Proposed using the first or a second letter for the element symbol. Jons Jacob Berzelius (1779-1848)

8. Modern Element Symbols • Each element has its own symbol. • In writing a symbol, we use 1 or 2 letters. • The first letter is always capitalized, the second is not. • Some elements kept symbols for Latin or Greek words. • Elements are grouped in the periodic table.

9. The Periodic Table

10. The Periodic Table • The periodic table is a system which helps to classify the elements. • In 1735, there were only 13 known elements; in 1850, there were 47; today there are over 100, including several man-made elements.

11. The periodic table we use today was devised by a Russian scientist named Dmitri Mendeleev in 1869. The Periodic Table (continued)

12. Mendeleev’s Periodic Table

13. Mendeleev’s Periodic Table

14. Mendeleev’s Periodic Table

15. Other Attempts…..

19. Other Attempts…..

21. Periodic Table Information A periodic table can tell us many things: • Elements are arranged in order of atomic numbers (number of protons in the nucleus) • Atomic weight or mass of an element (number of protons and neutrons) • Metals and non-metals are separated in the upper right corner by a zigzag line.

22. Metals and non-metals

23. Metals

24. Properties of metals • All solids at room temperature, except mercury (liquid) • Shiny • Malleable (bendable) • Good conductors of heat and/or electricity • Ductile (can be drawn into thin long wires) • Most react with acids • Located left of the staircase line in the periodic table.

25. Non-metals

26. Properties of non-metals • Most are gases, some are solids, bromine is the only liquid, • Dull • Brittle • Poor or nonconductors • Do not react with acids • Located right of the staircase line in the periodic table.

27. Metalloids (semi-metals) • Elements that have some properties of metals and some of nonmetals. • Include all elements on either side of the staircase line except AL and At. • Also includes one form of C, called graphite, which is dull and brittle (nonmetal) but is a good conductor of electricity (metal).

28. Periodic Table Information • Horizontal rows are called periods. • Vertical columns are called groups or families (all elements in the same group have similar characteristics). • The group number is the number of electrons in the outside level or orbit of an atom. These are called valence electrons. • The groups on the periodic table have different names: • Group A – Representative elements (1,2,13-18) • Group B – Transition elements (3-12)

29. Chemical Families (groups) • Group 1 (IA) – alkali metals • Group 2 (IIA) – alkaline earth metals • Group 17 (VIIA) – halogens • Group 18 (VIIIA) – noble gases • Rows on the bottom: • Lanthanide series • Actinide series

32. Chemical Families – Alkali metals • group 1, IA • Eg. Sodium, lithium - Show metallic properties - Highly reactive, especially with water; reactivity increases down the group - Cs and Fr are the most reactive metals.

33. Alkaline earth metals • Group 2, IIA • Eg. Calcium, magnesium - show metallic properties - less reactive than alkali metals; reactivity increases down the group

34. Halogens • Group 17, VIIA • Eg. Chlorine, fluorine - show nonmetallic properties - reactivity decreases going down the group; F is the most reactive nonmetal - react with metals to produce salts (ionic compounds) - react with hydrogen to form compounds that dissolve in water to form acids.

35. Noble Gases • Group 18, VIIIA • Helium, neon, argon - show nonmetallic properties - extremely low chemical reactivity