SIMPLE BINARY IONIC and COVALENT COMPOUNDS: Bonding, Naming and Formulas

Transcription

1 SIMPLE BINARY IONIC and COVALENT COMPOUNDS: Bonding, Naming and Formulas

2 What is an binary ionic compound? A binary ionic compound is composed of ions of two different elements - one of which is a metal, and the other a nonmetal. For example, sodium iodide, NaI, is composed of sodium ions, Na + (elemental sodium is a metal), and iodide ions, I - (elemental iodine is a nonmetal).

3 Rules for Naming Binary Ionic Compounds Rule 1. The cation (metal) is written first in the name; the anion is written second in the name. Cations donate their valence electrons. Rule 2. The name of the cation is the same as the (neutral) element from which it is derived (e.g., Na + = "sodium"). Rule 3. The anion (nonmetal) is named by adding the suffix - ide to the root of the element name (e.g., I - = "iodide"). Anions accept valence electrons to achieve a filled energy level (8 electrons) DO NOT USE PREFIXES TO INDICATE THE NUMBER OF ATOMS OF EACH ELEMENT IN AN IONIC COMPOUND!!!!!

4 RULES FOR WRITING FORMULAS OF IONIC COMPOUNDS 1. Write the cation (on the left) and the anion (on the right). In the superscript (above and to the right) position, write the charge of the ions, which are determined from the periodic table: Mg +2 N Move the absolute value (no sign) of each charge to become the subscript of the opposite atom. This is known as the crossover or criss- cross method: Mg +2 N - 3 Mg 3 N 2

5 IONIC COMPOUND FORMULA WRITING 3. If the subscripts have a common factor, they must be simplified by that common factor. For example: Ca +2 O - 2 Ca 2 O 2 4.In this case, she subscripts have a common factor of 2. To simplify, divide both subscripts by the common factor. This yields: Ca 2/2 O 2/2 Ca 1 O 1 5. HOWEVER, if any subscript is a 1, it is not written (it is an assumed 1, like x is assumed to be 1x in algebra). So: CaO

6 CHARGE BALANCE OF IONIC COMPOUNDS It is important to understand that the ratios in which ions combine is a result of the ions attempts to neutralize their overall charge. In the calcium oxide (CaO) example above, the calcium ion begins the process with a charge of 2+, and the oxygen begins with a charge of 2-. Combining one of each type of ion which pairs a 2+ charge with a 2- charge results in the charges cancelling each other out and resulting in a neutral charge for the formula unit.

7 WHAT IS A BINARY COVALENT COMPOUND? A binary covalent compound is composed of two different nonmetal elements that share electrons to achieve an octet in which each element has access to 8 valence electrons. Exception is hydrogen, it only needs 2 valence electrons to achieve stability. The resulting compound is also neutral For example, a molecule of chlorine trifluoride, ClF 3 contains 1 atom of chlorine (nonmetal) and 3 atoms of fluorine (nonmetal)

8 RULES FOR NAMING BINARY COVALENT COMPOUNDS Rule 1. The element with the lower group number is written first in the name; the element with the higher group number is written second in the name. Exception: when the compound contains oxygen and a halogen, the name of the halogen is the first word in the name.

9 RULES FOR NAMING BINARY COVALENT COMPOUNDS Rule 2. If both elements are in the same group, the element with the higher period number is written first in the name. Rule 3. The second element in the name is named as if it were an anion, i.e., by adding the suffix - ide to the name of the last element.

10 RULES FOR NAMING BINARY COVALENT COMPOUNDS Rule 4. Greek prefixes (next slide) are used to indicate the number of atoms of each nonmetal element in the chemical formula for the compound. Exception: if the compound contains one atom of the element that is written first in the name, the prefix "mono- " is not used. Note: when the addition of the Greek prefix places two vowels adjacent to one another, the "a" (or the "o") at the end of the Greek prefix is usually dropped; e.g., "nonaoxide" would be written as "nonoxide", and "monooxide" would be written as "monoxide". The "i" at the end of the prefixes "di- " and "tri- " are never dropped.

11 RULES FOR NAMING BINARY COVALENT COMPOUNDS prefix number indicated mono- 1 di- 2 tri- 3 tetra- 4 penta- 5 hexa- 6 hepta- 7 octa- 8 nona- 9 deca- 10

12 EXAMPLES OF BINARY COMPOUND NAMES CO carbon monoxide N 2 Cl 4 dinitrogen tetrachloride PH 3 phosphorus trihydride P 4 S 3 tetraphophorus trisulfide

13 NAMING BINARY COVALENT COMPOUNDS 1. Refer to periodic table of elements 2. Write symbol of each element 3. Use prefix system for naming. Dinitrogen monoxide N 2 O Carbon tetrachloride CCl 4 Sulfur hexafluoride SF 6

14 Venn Diagram 1. Label the title Ionic and Covalent Compounds (on line provided). 2. Label the left side of the Venn diagram Ionic Compounds (on line provided). 3. Label the left side of the Venn diagram Covalent Compounds (on line provided). 4. Write your name on the back of the paper. 5. Fill out the Venn Diagram using the information on the next slides. 6. Refer to the PowerPoint as needed. 7. Don t forget the middle section is characteristics shared by both ionic and covalent compounds.

15 Occurs between a metal element and a nonmetal element. Occurs between a nonmetal element and a different nonmetal element. Share valence electrons. Donate or accept valence electrons. Contain a nonmetal Contains a positive ion (cation). No prefixes are used in naming. The suffix of the last element is changed to ide.

16 Use the criss- cross OR swap & drop method to write formula. Contains a negative ion (anion). Greek prefixes used for naming the compound. Form compounds to achieve stability and neutrality. Greek prefixes used to indicate the number of atoms of each element in the formula of the compound. Include 2 ionic formulas and names not featured in the PowerPoint. Include 2 covalent formulas and names not featured in the PowerPoint. Turn in your completed Venn Diagram to your teacher.