AP Chapter 2

1. AP Chapter 2 Chemical Equations and Reactions

2. Formulas • H2O • Ba(C2H3O2)2

3. Empirical and Molecular Formulas

4. Atomic mass unit • The atomic mass unit (u), is a unit of mass used to express atomic and molecular masses. • It is the approximate mass of a hydrogen atom, a proton, or a neutron. • By definition the atomic mass unit is equal to one-twelfth of the mass of a carbon-12 atom.

5. The Atom • The nucleus is very small, dense, and positively charged. • Electrons surround the nucleus. • Most of the atom is empty space

6. Subatomic Particles

7. Atomic Number (Z) • The number of protons in the nucleus of an atom. • The identifying characteristic of an element.

8. Mass Number • The sum of the protons and neutrons in the nucleus of an atom.

9. Isotopes

10. Isotopes • This is the symbol for carbon-12. • Atomic number is 6. • Mass number is 12.

11. Isotopes • This is the symbol for carbon-12. • Atomic number is 6. • Mass number is 12. • Write the symbols for carbon-13 and carbon-14.

12. Isotopes

13. What is the average mass of a carbon atom?

14. What is the average mass of a carbon atom? 12.01

15. Atomic Mass • The atomic mass of carbon is 12.01u.

16. Atomic Mass • The atomic mass of carbon is 12.01u. • Atomic mass is the average mass of all the isotopes of an atom. It takes into account the different isotopes of an element and their relative abundance.

17. How many electrons, protons and neutrons are in an atom of actinium with a mass number of 221?

18. How many electrons, protons and neutrons are in an atom of actinium with a mass number of 221? 89p+ 89e- 132n0

19. How many electrons, protons and neutrons are in an atom of rhodium-105?

20. How many electrons, protons and neutrons are in an atom of rhodium-105? 45p+ 45e- 60n0

21. Families of the Periodic Table

22. The Noble Gases • Elements in group 18 • All are gases. • VERY non-reactive. • Have a full outer energy level.

23. The Octet Rule • The octet rule states that an element's outer energy level is full and most stable when it contains eight electrons. • This stability is the reason that the noble gases are so non-reactive.

24. Exception to the Octet Rule • The first energy level can only hold two electrons and so elements such as Hydrogen and Helium that only have one energy level follow a “duet rule”.

25. Ion Vocabulary • An ion is an atom or group of atoms that have a charge. • A monatomic ion is an atom with a charge. • The charge on the atom is called an oxidation number. • A polyatomic ion is a group of atoms with a charge. • A cation is a positive ion. • An anion is a negative ion.

26. 11 protons 11 electrons 11 protons 10 electrons Na+ Na 17 protons 18 electrons 17 protons 17 electrons Cl- Cl An ion is an atom, or group of atoms, that has a net positive or negative charge. cation – ion with a positive charge If a neutral atom loses one or more electrons it becomes a cation. anion – ion with a negative charge If a neutral atom gains one or more electrons it becomes an anion. 2.5

27. Ionic • When an element that easily loses electrons (a metal) reacts with an element that easily gains electrons (a nonmetal), one or more electrons are transferred. • This creates two ions which are held together by an ionic bond. • A compound that contains ions is called an ionic compound.

28. a

29. Formula Unit A formula unit is the empirical formula of an ionic compound. It is the lowest whole number ratio of ions represented in an ionic compound. Examples include ionic NaCl and K2O. Ionic compounds do not exist as individual molecules; a formula unit thus indicates the lowest reduced ratio of ions in the compound.

30. Covalent • When atoms share electrons the bond created is said to be covalent. Covalent bonds often form between nonmetal atoms. • These covalently bonded atoms act as single units called molecules. • A compound made up of molecules is a covalent compound.

33. Polyatomic Ions Note that these are charges and not oxidation numbers.

34. Types of monatomic ions and the rules for naming them • The periodic table is useful in naming the monatomic ions.

35. Monatomic cations with one oxidation number • The cations from the periodic table which have a single oxidation number are as follows: Group 1 (+1), Group 2 (+2), Ag+, Cd2+, Zn2+, and Al3+. • These types of ions are named by using the name of the element followed by the word ion. • Na+ sodium ion • Ba2+ barium ion • Zn2+ zinc ion • We can use the roman numeral from the periodic table to identify the oxidation number for these ions.

36. Monatomic cations with multiple oxidation numbers • All other cations that are not listed in the previous category (“cations with one oxidation number) are considered to have the possibility of multiple oxidation numbers. • These type of ions are named by using the name of the element followed by a Roman numeral to indicate the oxidation number. • Cu2+ copper (II) • Pb4+ lead (IV) • Mn7+ manganese (VII)

37. Monatomic anions • All anions from the periodic table are named by changing the ending of the element’s name to –ide. • F- fluoride ion • O2- oxide ion • N3- nitride ion • Count back from the noble gases starting at zero to determine the oxidation number.

38. Name these monatomic ions • Rb+ • P3- • Fe3+ • Br‾ • Mn4+ • Cd2+

39. Write the formula for these monatomic ions. • Sulfide • Lead (II) • Barium ion • Chromium (IV) • Aluminum ion • Carbide

40. Formulas of Ionic Compounds: • Formulas for ionic compounds can be written by the following steps:

41. Formulas of Ionic Compounds: • Formulas for ionic compounds can be written by the following steps: • (1) Write the formula for the cation and anion (Don’t forget to include the charge of each ion).

42. Formulas of Ionic Compounds: • Formulas for ionic compounds can be written by the following steps: • (1) Write the formula for the cation and anion (Don’t forget to include the charge of each ion). • (2) Decide how many cations and anions are needed so that the sum of their charges balances out to be zero.

43. Formulas of Ionic Compounds: • Formulas for ionic compounds can be written by the following steps: • (1) Write the formula for the cation and anion (Don’t forget to include the charge of each ion). • (2) Decide how many cations and anions are needed so that the sum of their charges balances out to be zero. • (3) Write the formula of the compound by writing the number of cations followed by the number of anions which you used in step #2. Remember not to include the charges of the ions since now they balance out to be neutral. (*Note when using more than one polyatomic ion the polyatomic ion must be written in parentheses).

44. Write the formula for barium chloride

45. Write the formula for iron (II) oxide

46. Write the formula for calcium phosphate

47. Write the formula for ammonium carbonate

48. Write the formulas for the following compounds • cobalt (II) chloride • lithium sulfate • ammonium dichromate (d) aluminum oxide (e) boron (III) phosphide (f) Chromium (V) nitrate

49. Naming Ionic Compounds • When naming ionic compounds the following steps are followed:

50. Naming Ionic Compounds • When naming ionic compounds the following steps are followed: (1) Separate the compound into its positive and negative parts (Note that the positive part of a compound will be only the first element with the exception of ammonium which is NH4+)