Write Lewis structures for the following ionic compounds: (a) calcium chloride; (b) barium sulfi

Write Lewis structures for the following ionic compounds:...

Key Concepts

Ionic Compounds

Ionic compounds are chemical compounds composed of cations and anions that are held together by electrostatic forces. These compounds typically form between metals, which lose electrons to form positively charged ions, and non-metals, which gain electrons to form negatively charged ions. The resulting structure must be electrically neutral overall, and the arrangement of ions in the crystal lattice maximizes attractive interactions while minimizing repulsions.

Ionic Bonding

Ionic bonding involves the transfer of electrons from one atom (usually a metal) to another (usually a non-metal), resulting in the formation of ions. This process leads to the creation of oppositely charged ions which then attract each other via electrostatic forces. Understanding ionic bonding is crucial for predicting the structure, properties, and behavior of ionic compounds.

Lewis Structures

Lewis structures are diagrammatic representations of molecules that show the arrangement of valence electrons around atoms. In the context of ionic compounds, Lewis structures help visualize how electrons are transferred from one atom to another, resulting in the formation of ions. Although ionic bonds are typically not represented by sharing of electrons as in covalent bonds, Lewis structures still illustrate the attainment of stable electron configurations for the ions involved.

Valence Electrons

Valence electrons are the electrons located in the outermost electron shell of an atom. These electrons play a key role in chemical bonding because they are the ones involved in either gaining, losing, or sharing during bond formation. Counting valence electrons correctly is essential when drawing Lewis structures since it ensures that the depicted electron configurations accurately represent the ions’ tendencies to achieve stability.

Octet Rule

The octet rule is a fundamental principle stating that atoms tend to gain, lose, or share electrons in order to have a full set of eight valence electrons, thereby reaching a configuration similar to that of a noble gas. In ionic compounds, atoms achieve this stable electron arrangement by transferring electrons completely, which results in the formation of ions that have complete outer electron shells.

Charge Balance

Charge balance is the principle that the total positive charge from the cations and the total negative charge from the anions in an ionic compound must equal zero. When writing formulas and Lewis structures for ionic compounds, it is important to determine the correct ratio of ions so that their charges cancel out. This ensures that the compound is electrically neutral, reflecting its real-world stability and composition.

Transcript

00:01 Before drawing the lewis structure, we need to write the formula for the ionic compound, and this is based on the ionic charges, and we'll be walking through this in a second.

00:09 And then next, we will separate all the ions based on this formula, and then we will add valence electrons as dots.

00:17 And then lastly, we will add charges to each one of these ions, and that will complete our lewis drawing for each one of them.

00:24 So let's just walk through this.

00:25 And so first we have calcium chloride, and we know that the element.

00:30 For calcium is ca and then chloride is cl.

00:33 And so we can look at the periodic table and look at the ionic charges first to see that calcium will have a plus two charge and chloride will have a one minus charge.

00:47 And so what we're going to do now to find out how many of each ion we're going to have and to finish writing the formula out is we're going to do something called like the crisscross method.

01:00 I'm not sure what.

01:01 Your instructor calls it, but you're going to take this number and you're going to bring it down, and then you're going to take this number and bring it down here.

01:11 And so this will result in c -a -c -l -2.

01:17 And so this means that we are going to have two calcium, or sorry, two chloride ions.

01:24 And so because we know this, we can go ahead and write these ions out separately.

01:28 And so this means that we are on step three now.

01:33 And so we're going to add the valence electrons to each ion as dots.

01:37 And so first for chloride, we see that based on this right here, we can see that this group, it will have seven.

01:47 And so we can draw these around.

01:52 And so we know that the fluoride ion will have a one minus charge.

02:00 And so, meaning that we will add one electron to this, bringing it to a full octet.

02:09 And so, again, let's do this on the other chloride ion.

02:14 And so we know we have one, two, three, four, five, six, seven.

02:20 And then we have that one minus charge.

02:23 And so because of this, we will add another electron.

02:29 And so now moving on to our calcium ion.

02:32 Let's see, looking at the purok table, we know that here we can see that it will have a plus two ionic charge, and then it will have two valence electrons.

02:47 And so because we know this, this means that we will have to subtract two of the electrons because of this plus two charge.

02:56 And so this leaves with just the calcium.

03:01 There are no dots because there are no longer any valence electrons.

03:05 And so the overall ionic charge is a 2 plus.

03:12 And so we can leave it like this.

03:17 So let's go ahead and move on to our next one, barium sulfide.

03:21 And so here we know that this is going to be bas.

03:25 And so let's look at our ionic charges first here.

03:29 And we can see that with barium, this will have a plus 2 charge.

03:34 And sulfide is going to have a minus two charge...