1. Chapter 2 cont’ Reacting Atoms
when elements undergo chemical reactions, the reacting elements do not turn into other elements
Dalton’s Atomic Theory
since the number of protons determines the kind of element, the number of protons in the atom does not change in a chemical reaction
however, many reactions involve transferring electrons from one atom to another

2. Mixtures and Chemical Compounds

3. Molecules and Covalent Bonds
compounds are made of atoms held together by chemical bonds
covalent bonds result when two atoms share some of their electrons
Nonmetal + Nonmetal
Molecule: The unit of matter that results when two or more atoms are joined by covalent bonds.

4. Molecules and Covalent Bonds

5. Naming Chemical Compounds
Binary Molecular Compounds
Because nonmetals often combine with one another in different proportions to form different compounds, numerical prefixes are usually included in the names of binary molecular compounds.

6. Naming Covalent Compounds
Chapter 2: Atoms, Molecules, and Ions
2/17/2019
Naming Covalent Compounds
N2F4
The first element listed is more cationlike and takes the name of the element.
The second element listed is more anionlike and takes the name of the element with an “ide” modification to the ending.
The prefix is added to the front of each to indicate the number of each atom.
dinitrogen tetrafluoride
Copyright © 2008 Pearson Prentice Hall, Inc.

7. Naming Covalent Molecules
Chapter 2: Atoms, Molecules, and Ions
2/17/2019
Naming Covalent Molecules
Binary Molecular Compounds
Whenever the prefix ends in “a” or “o” and the element name begins with a vowel, drop the “a” or “o” in the prefix.
N2O4
dinitrogen tetroxide
Whenever the prefix for the first element is “mono,” drop it.
CO2
carbon dioxide CO
carbon monoxide
Copyright © 2008 Pearson Prentice Hall, Inc.

8. Name the following
NO2
PCl5
I2F7

9. Example – Binary Molecular dinitrogen pentoxide
Identify the symbols of the elements
nitrogen = N
oxide = oxygen = O
Write the formula using prefix number for subscript
di = 2, penta = 5
N2O5

10. Write formulas for the following
dinitrogen tetroxide
sulfur hexafluoride
diarsenic trisulfide

11. Ions and Ionic Bonds
Ionic Bond: A transfer of one or more electrons from one atom to another. A strong electrical attraction between charged particles. Typically a metal bonded to a nonmetal.
Ion: A charged particle
Cation: A positively charged particle. Metals tend to form cations.
Anion: A negatively charged particle. Nonmetals tend to form anions.

12. Charged Atoms when atoms gain or lose electrons, they acquire a charge
charged particles are called ions
when atoms gain electrons, they become negatively charged ions, called anions (Cl-)
when atoms lose electrons, they become positively charged ions, called cations (Na+)
ions behave much differently than the neutral atom
e.g., The metal sodium, made of neutral Na atoms, is highly reactive and quite unstable. However, the sodium cations, Na+, found in table salt are very nonreactive and stable

13. Ions and Ionic Bonds 2 1 Na + Cl2 Na+ + Cl–
In the formation of sodium chloride, one electron is transferred from the sodium atom to the chlorine atom. 2 1
Na Cl2
Na+ + Cl–
Sodium is very reactive in water!
Chlorine gas can kill someone (Fritz Haber, WWI).
Sodium chloride: preservative, common food additive

14. Atomic Structures of Ions
Nonmetals form anions
For each negative charge, the ion has 1 more electron than the neutral atom
F = 9 p+ and 9 e-, F ─ = 9 p+ and 10 e-
Metals form cations
For each positive charge, the ion has 1 less electron than the neutral atom
Na atom = 11 p+ and 11 e-, Na+ ion = 11 p+ and 10 e-

15. Naming Chemical Compounds
Cation Charges for Typical Main-Group Ions 1+ 2+ 3+
Metals tend to form cations. Note some in 3A and 4A with multiple charges.

16. Naming Chemical Compounds
Cation Charges for Typical Main-Group Ions 3– 2– 1–
Nonmetals tend to form anions. Noble gases do not naturally form ions in this sense.

17. Examples
Predict the charge and identify the number of proton and electron from that ion
Mg 
Al 
O 
P 

18. Naming Chemical Compounds
Ionic Compound: A neutral compound in which the total number of positive charges must equal the total number of negative charges.
Binary Ionic Compounds
Sodium chloride:
Na+
Cl–
NaCl
Magnesium oxide:
Mg2+
O2–
MgO
Aluminum sulfide:

19. Naming Chemical Compounds
Some transition metals form more than one cation.

20. Naming Chemical Compounds
Use Roman numerals in parentheses to indicate the charge on metals that form more than one kind of cation.
Binary Ionic Compounds
Iron(III) oxide:
Fe3+
O2–
Fe2O3
__________:
Sn2+
Cl–
SnCl2
The common system (stannous, stannic, etc.) is still used, but its use is becoming less frequent.
Mn2+
N3–
___________:

21. Polyatomic ions Memorize these ions
Polyatomic ions are covalently bonded atoms with a net charge.

22. Naming Chemical Compounds
Polyatomic Ionic Compounds
Sodium hydroxide:
Na+
OH–
NaOH
Magnesium carbonate:
Mg2+
CO32–
MgCO3
Sodium nitrite: _____ ____ ____
Chromium(II)bromate: _____ _____ _____