Lab #4 Periodic Table – Part 2

1. Lab #4Periodic Table – Part 2 Chemistry 108 Instructor:Robert Goldman

2. Periodic Trends – Electronegativity • Electronegativity is the attraction an atom has for its bonding valence electrons. • Electronegativity increases from left to right and from bottom to top of the periodic table.

3. Periodic Trends – Electronegativity

4. Periodic Trends – Electronegativity • The amount of energy required to remove a valence electron from an atom. • More electronegative atoms have higher ionization energies.

5. Periodic Trends – Ionization energy

6. Periodic Trends – Atomic size • Atomic size tends to increase LEFT to RIGHT across the periodic table and from TOP to BOTTOM down groups. • This is due to valence electrons occupying shells further from the nucleus.

7. Periodic Trends – Atomic size

8. Periodic Trends – Bonding Patterns • Elements usually form a certain number of bonds, depending on their location in the periodic table. • Group 14 elements (C, Si, Ge, Sn, Pb) tend for form 4 bonds. • For each group you move right, the normal number of bonds formed decrease by one.

9. Periodic Trends – Bonding Patterns • Therefore… • Group 14 elements tend to form 4 bonds. • Group 15 elements tend to form 3 bonds. • Group 16 elements tend to form 2 bonds. • Group 17 elements tend to form 1 bond. • Group 18 elements (noble gases) tend not to form any bonds (stable). • Hydrogen forms only one bond.

10. Chemical Nomenclature • You are expected to be able to provide appropriate names for simple binary and ternary compounds. • Binary = Two elements • Ternary= Three elements

11. Naming Binary Compounds • Binary compounds begin with names based on the most metallic element present in the compound. • Ex. NaCl – sodium is more metallic than chlorine, so “sodium” is the first part of the name of this compound.

12. Naming Binary Compounds • Next, the name of the less metallic element is added, with a suffix of –ide. • Ex. chlorine becomes chloride • Overall name of compound is sodium chloride.

13. Naming Binary Compounds • How would you name the following? • K2S • MgO

14. Naming Binary Compounds • Binary compounds can also form from two non-metals. • In this case, the name of the most metallic element (lowest in electronegativity) is used as the first part of the compound name.

15. Naming Binary Compounds • When two non-metals combine, they can form several different compounds. • Unique names are assigned to distinguish these. • Remember these important prefixes!!!

16. Naming Binary Compounds • Example • Phosphorous and chlorine combine to form PCl3 and PCl5. • In order to distinguish between the two: • PCl3 is called phosphorous trichloride • PCl5 is called phosphorous pentachloride

17. Naming Binary Compounds • How would you name the following? • SiO2 • MgO4

18. IMPORTANT • DO NOT use these prefixes for compounds formed between a metal and a non-metal. • LiF is lithium floride NOT lithium monoflouride!

19. Naming Binary Compounds • Compounds containing transition elements (center of the periodic table, no group #’s) are a bit different. • Most have a valence of two and form two bonds (+2 ion) by losing two electrons. • They may, however, form other ions by losing different numbers of electrons.

20. Naming Binary Compounds • The charge of the transition element must always be shown in the name of the compound. • This is done by adding the charge in roman numerals in parenthesis after the ion. • Ex: Iron (II) oxide – Iron with TWO BONDS

21. Naming Binary Compounds • So… • How many bonds does copper form in copper (II) chloride? • Cu forms one bond, Cl forms one bond-- CuCl • What is the charge on titanium in titanium (IV) oxide? • Ti forms four bonds in this case, O (group VI) forms two bonds– TiO2

22. Naming Ternary Compounds • Ternary compounds contain three different elements.

23. Naming Ternary Compounds • Many of these are acids or salts of acids. • Salt= compound formed from an acid + a base • A salt is formed when the hydrogen from an acid is replaced by a metal. • Memorize the following acids:

24. Naming Ternary Compounds • Chloric acid trends • HClO4 = perchloric acid (1 extra oxygen) • HClO3 = chloric acid (base acid) • HClO2 = chlorous acid (1 less oxygen) • HClO = hypochlorous acid (2 less oxygens) • This is on P. 95 in your textbook.

25. Naming Ternary Compounds • Example: • HIO3 is iodic acid • HIO2 becomes iodous acic • Etc…

26. Naming Ternary Compounds • To name a salt of a ternary acid… • 1. Name the metal that replaced the hydrogen. • 2. Name the acid that the salt is derived from but change the suffix to show the compound is no longer an acid (-ic becomes –ate,-ous becomes –ite). • Ex. LiNO3 has a base acid of HNO3 (nitric acid) • The salt will then be named lithium nitrate.

27. Naming Ternary Compounds • If an acid has two hydrogens, both are replaced to form a salt. • Group I metals replace one hydrogen each. • Ex: Na2SO4 (derived from H2SO4) • Name= sodium sulfate

28. Naming Ternary Compounds • Group II metals will replace two hydrogens each. • CaSO4 (derived from H2SO4) • Name=calcium sulfate

29. Today in lab… • We will be determining the percent water in a hydrated salt by weighing before and after dehydrating it. • Follow directions in lab manual. • Be careful with hot crucibles! • WEAR GOGGLES AT ALL TIMES! • Let me know if you have questions.