IONIC BONDING NOTES (Chapter 7 Section 1)

Transcription

1 IONIC BONDING NOTES (Chapter 7 Section 1) I. Introduction Because all atoms want to have a total of, atoms will,, or electrons to form bonds. One of these bonds is an. A. Ionic Bond - is when a charged ion ( ) is attracted to a charged ion ( ). - Since usually form cations and usually form anions, bonds often occur between metallic and nonmetallic ions. B. Ionic compound - is a compound made up of ( positive ions) and (negative ions). - Since the charge must balance with the charge, ionic compounds are ( or have a total zero charge). - The in an ionic compound are arranged in such a way as to separate the and from each other as much as possible. C. Properties: - (indicates that the ionic bond is very strong) - are - break at - many in water - are of heat and electricity when dissolved in water - when (liquid state) are good conductors - conduct when in the state D. The Octet Rule: Many atoms are not very when they are. For instance, and are unstable alone, but when combined to form (table salt) the compound is. If we look at the outer electron configuration for Na and Cl we can see why. Na: Cl:

2 When Na its valence electron, its configuration becomes the same as, which is very stable since it is the same as a. When Cl an electron, its configuration becomes, which is the same as that of which is a noble gas. **All atoms want to be like noble gases and will therefore and electrons to become like a noble gas. This applies to the elements (or the A group elements), the transition metals. The states that atoms tend to,, or electrons in order to acquire a of (or 8) valence electrons. ( will have a full set of valence electrons with 2, since they only have one energy level and this energy level can only hold 2 electrons at the most.) E. Lewis Electron Dot Diagrams: Since the electrons are the only electrons involved in, we can represent these electrons by drawing These diagrams were developed by an American chemist,. To draw these diagrams, or are placed around an elements to represent the number of electrons. For elements with that 8 valence electrons, the dots are placed first and then in around the element symbol on the sides as if a box were drawn around the element. (do not draw a box) See Examples Below:

3 F. Types of Ions: - Monatomic Ions are ions. These can be either or. - Polyatomic Ions are ions. These can be either anions or cations. These ions are made up of ions which have an as a unit. It is best to place these in when using them in formulas. See list of polyatomic ions provided by the teacher. We will be learning how to write formulas for and name ionic compounds. II. Writing Formulas for Ionic Compounds: We will be dealing only with Compounds. These compounds are made up of parts, a and an. The cation and anion can be or. We will look at these later. We will be writing formulas referred to as formulas. These formulas represent the of atoms or ions in a compound. Element symbols represent the and subscripts represent the. For example Al 2 O 3 has 2 Al ions and 3 O ions. To correctly write these ionic formulas, we will use the. Steps: 1. Write the element symbols for the and the, placing the cation on the and the anion on the. 2. Write the of each ion as a. - Recall, the tells us the number of electrons which help us determine the charge. - Group 1A has valence electron and will lose it to become an. - Group 2A has Valence electrons and will lose it to become a. - Group 3A =, - Group 4A =, - Group 5A = ( has 5 valence electrons and will gain 3 electrons), - Group 6A =,

4 - Group 7A =. - The for the polyatomic ions are found on the list of polyatomic ions. 3. the 2 charges (only the, not the ) moving them downward from one ions superscript to the other ions subscript. ***Note: Do not write the in the subscript. Do not write as a subscript (no # indicates a 1). Ratio must be the ratio (if have two subscripts of 2, you would make them both 1, since the both can be divided by 2) Remember to put around polyatomic ions when you use them in formulas. Some transition metals have. The charge of these ions will be indicated by a in parentheses. Examples: Write the formula formed between potassium and phosphorus ( or the compound potassium phosphide) 1. Symbols for elements: 2. Assign charges: 3. Criss Cross : Remember we do not write the 1 as a subscript on P. Write the formula for calcium nitrate 1. Symbols for elements: 2. Assign charges: 3. Criss Cross : Remember we do not write the 1 as a subscript on Ca.

5 More Examples: III. Naming Ionic Compounds: When given the formula for an ionic compound, naming the ionic compound is fairly easy. For a simple ionic compound (only monatomic ions), you simply write the - for the first. Next write the of the after modifying the ending by placing as a suffix. For example oxygen would be written as, nitrogen would be. If a formula has a ion, you simple write the name of the polyatomic ion as it on the list. If the is one of the elements in the group which has multiple charges (see periodic table with charges to see which transition metal apply), you indicate the charge on the by placing the charge in parenthese as a. You will have to determine the charge. Se example below to determine the charge. Examples: Name the following compound: Al 2 S 3

6 Name Ca(OH) 2 Name Cu 2 O Cu is a transition metal with multiple charges (it can be 2+ or 1+). To figure out which Cu to use, we have to figure it out. We know that the total charge on the compound in zero. We also know that the charge on O is 2-. In order for the total to be zero, the total positive charge on Cu must be 2+. Since we have 2 Cu ions in this compound (comes from subscript of 2), each ion must have a 1+ charge for a total of 2+. So the charges would be as follows: