Housekeeping: We are now moving into chemical bonding.
Agenda:
1. Discussion of ion formation.
2. How ionic bonds are formed.
3. How covalent bonds are formed.
4. Determination of polarity.
Content Review:
Links: Chemical Bonding This page contains PowerPoints that cover ionic and covalent bonding and a summary table.
For those of you that prefer PowerPoints, here they are:
Ionic Compounds Covalent Compounds Chemical Names & Formulas
Textbook Readings: Chapter 7, 8 & 9, respectively.
Student Missions:
Mission 1: Ions, Ions, Ions!
Mission Objectives. You should be able to...
1. Determine which elements form cations and which elements form anions.
2. Contemplate the structure of an ionic bond based on valence electrons.
3. Predict the name of an ionic compound and a covalent compound.
Recall that the group number on the periodic table represents the number of valence electrons in that group. Also recall that group 18, the noble gases, have stable octets. The objective for any element that is not a noble gas is to lose or gain electrons to have a noble gas configuration. Stability is key.
Elements in G1 will LOSE their valence electrons to form ions with a +1 charge. Elements in G2 will LOSE theirs to form ions with a +2 charge. Elements in G13 will lose theirs to form ions with a +3 charge. Any time an element LOSES a valence electron, a cation is formed. Cations are positively charged ions. Metallic elements form cations.
Conversely, elements in G15 will GAIN 3 electrons to form ions with a -3 charge. Elements in G16 will GAIN 2 electrons to form ions with a -2 charge, and elements in G17 will GAIN 1 electron to form an ion with a -1 charge. Any time an element GAINS a valence electron, an anion is formed. Anions are negatively charged ions. Nonmetals form anions.
This sweet little 10-second interactive shows what happens to the size of atoms when ions are formed. Make note of which elements will get smaller and which will get bigger.
For more on ion formation, see what David Weightman has to say about it. It's three minutes long.
Agenda:
1. Discussion of ion formation.
2. How ionic bonds are formed.
3. How covalent bonds are formed.
4. Determination of polarity.
Content Review:
Links: Chemical Bonding This page contains PowerPoints that cover ionic and covalent bonding and a summary table.
For those of you that prefer PowerPoints, here they are:
Ionic Compounds Covalent Compounds Chemical Names & Formulas
Textbook Readings: Chapter 7, 8 & 9, respectively.
Student Missions:
Mission 1: Ions, Ions, Ions!
Mission Objectives. You should be able to...
1. Determine which elements form cations and which elements form anions.
2. Contemplate the structure of an ionic bond based on valence electrons.
3. Predict the name of an ionic compound and a covalent compound.
Recall that the group number on the periodic table represents the number of valence electrons in that group. Also recall that group 18, the noble gases, have stable octets. The objective for any element that is not a noble gas is to lose or gain electrons to have a noble gas configuration. Stability is key.
Elements in G1 will LOSE their valence electrons to form ions with a +1 charge. Elements in G2 will LOSE theirs to form ions with a +2 charge. Elements in G13 will lose theirs to form ions with a +3 charge. Any time an element LOSES a valence electron, a cation is formed. Cations are positively charged ions. Metallic elements form cations.
Conversely, elements in G15 will GAIN 3 electrons to form ions with a -3 charge. Elements in G16 will GAIN 2 electrons to form ions with a -2 charge, and elements in G17 will GAIN 1 electron to form an ion with a -1 charge. Any time an element GAINS a valence electron, an anion is formed. Anions are negatively charged ions. Nonmetals form anions.
This sweet little 10-second interactive shows what happens to the size of atoms when ions are formed. Make note of which elements will get smaller and which will get bigger.
For more on ion formation, see what David Weightman has to say about it. It's three minutes long.
Ionic compounds are formed when a cation bonds with an anion through the transfer of valence electrons. Another way of saying this is that an ionic compound forms when a metal bonds with a nonmetal.
For example, the sodium atom will transfer its one valence electron to chlorine, an atom with seven valence electrons. Sodium does not need it's valence electron, and chlorine craves to have one more valence electron, so the ionic bond is easily formed between them. This pattern holds true for any G1 element bonding with a G17 element. The pattern also works for G2 and G16 elements, and G13 and G15 elements. I call these perfect pairings, because they result in 1:1 compounds.
Of course, nothing is perfect because any metal can bond with any nonmetal. So there are compounds with ratios greater than 1:1. It's not difficult because it's all about balancing charges. Tyler DeWitt talks you through it. It would be helpful to have your periodic table handy.
For example, the sodium atom will transfer its one valence electron to chlorine, an atom with seven valence electrons. Sodium does not need it's valence electron, and chlorine craves to have one more valence electron, so the ionic bond is easily formed between them. This pattern holds true for any G1 element bonding with a G17 element. The pattern also works for G2 and G16 elements, and G13 and G15 elements. I call these perfect pairings, because they result in 1:1 compounds.
Of course, nothing is perfect because any metal can bond with any nonmetal. So there are compounds with ratios greater than 1:1. It's not difficult because it's all about balancing charges. Tyler DeWitt talks you through it. It would be helpful to have your periodic table handy.
Practice with this interactive.
Mission 2: Sharing is Caring!
Mission Objectives. You should be able to...
1. Determine when covalent bonds are formed and which elements form them.
2. Predict the name of an ionic compound and a covalent compound.
Covalent bonds are the result of valence electrons being shared in order to achieve stable octets. If you think back...way back...to the short lesson on Lewis Dot, you'll recall that certain elements contained a certain number of dots that represented their valence electrons.
Mission 2: Sharing is Caring!
Mission Objectives. You should be able to...
1. Determine when covalent bonds are formed and which elements form them.
2. Predict the name of an ionic compound and a covalent compound.
Covalent bonds are the result of valence electrons being shared in order to achieve stable octets. If you think back...way back...to the short lesson on Lewis Dot, you'll recall that certain elements contained a certain number of dots that represented their valence electrons.
Anyhoo, if you take a look at groups 15, 16 & 17 (the nonmetals), this is where covalent bonding takes place. These elements can bond with themselves to share a pair (or two, or three) of electrons to form stable octets. Take a look below. Fluorine will share a pair of electrons with another fluorine and a single covalent bond is formed (represented by a line).
Group 16 elements will share two pairs of electrons (double covalent bond) and group 15 elements will share three pairs of electrons (triple covalent bond). Again, the goal is stability. The Octet Rule rules all.
There are seven elements that are found in nature covalently bonded to each other. They are called diatomic elements. A useful memory aid is HONI Bring Fried Clams. So when you're writing these elements in chemical equations, you need to make sure you write them correctly.
Coordinate covalent bonds are bonds where one atom contributes both bonding electrons. You demonstrate them in structural formulas using an arrow that shows where the electrons came from. Once formed, the coordinate covalent bond is just like any other bond. Carbon monoxide is a good example of this.
Image courtesy of mrdchemcwiki.wikispaces.com
There are seven elements that are found in nature covalently bonded to each other. They are called diatomic elements. A useful memory aid is HONI Bring Fried Clams. So when you're writing these elements in chemical equations, you need to make sure you write them correctly.
Coordinate covalent bonds are bonds where one atom contributes both bonding electrons. You demonstrate them in structural formulas using an arrow that shows where the electrons came from. Once formed, the coordinate covalent bond is just like any other bond. Carbon monoxide is a good example of this.
Image courtesy of mrdchemcwiki.wikispaces.com
Polyatomic ions are a group of atoms that are tightly bound that behaves as a unit and has either a positive or negative charge. I gave you an ion reference chart, which contains a comprehensive list of polyatomic ions. You need to print a copy and keep it with your periodic table. Don't lose it.
Get familiar with covalent bonding using this interactive.
We will practice writing and naming ionic and covalent compounds.
Get familiar with covalent bonding using this interactive.
We will practice writing and naming ionic and covalent compounds.
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