Write formulas for each of the following compounds: a. sodium fluoride b. calcium oxide c. potas

Write formulas for each of the following compounds: a....

Key Concepts

Oxidation States and Nomenclature in Transition Metals

Transition metals often have multiple oxidation states. Roman numerals in compound names indicate the oxidation state of the metal ion, which directly influences how many anions are needed to achieve charge neutrality. This is key to determining the correct chemical formula for compounds involving transition metals.

Ion Charges and Periodic Trends

The charges of individual ions are generally predicted by their positions in the periodic table and common oxidation states. For example, elements in Group 1 typically form +1 cations and those in Group 17 typically form -1 anions. Recognizing these common charges allows chemists to write formulas based on the known behavior of elements.

Ionic Bonding

Ionic bonding refers to the chemical bonding process where atoms transfer electrons, leading to the formation of positive ions (cations) and negative ions (anions) that attract each other. In ionic compounds, this attraction results in a stable, electrically neutral lattice structure. Understanding ionic bonding is crucial for writing correct chemical formulas as it explains why certain ions combine in specific ratios.

Charge Balance in Ionic Compounds

Every ionic compound must be electrically neutral, which means that the total positive charge from the cations must equal the total negative charge from the anions. This principle of charge balance drives the determination of the appropriate subscripts in a chemical formula to indicate the ratio of ions present in the compound.

Transcript

00:02 When we're writing the formula for binary compounds, the first thing that we want to do is break it apart into its different ions, so cat ion and anion.

00:14 And then we're going to assign charges.

00:16 So for the example, sodium fluoride, we're going to break it down into its ions, sodium and fluoride, and we'll write those symbols, and we'll assign it charges.

00:36 And in order to do that, we'll have to look at the periodic table and just see which group.

00:40 It belongs to.

00:41 So sodium's going to have a plus one charge because it's in that plus one group of cations.

00:50 Fluoride's going to have a negative one charge because it's in that negative one group of anions.

00:58 And then what we're going to do is to cross over those charges and turn them into subscripts.

01:07 So sodium gets a one because fluorine has a one.

01:13 And fluorine gets a one because sodium got a one.

01:17 And now what you're going to do is just figure out what's the largest common factor that goes into both of those numbers.

01:22 So in this case, it is a one.

01:24 You would divide both of those numbers by one because that's the largest common factor.

01:29 And what we end up with is one sodium and one fluoride.

01:48 So the formula for that would be n -a -f.

01:57 The next example would be calcium oxide.

02:02 So we're going to break it apart into its ions.

02:06 We're going to have calcium.

02:10 We'll write the symbol, and then oxide.

02:14 So that's ox.

02:16 And then we'll write the charges.

02:17 So we know by looking at the periodic table that calcium belongs to that group two of positive cations.

02:25 So we'll give it a charge of plus two.

02:32 Same thing with oxygen.

02:33 It actually has a minus two because it's in that negative two group of anions.

02:43 And now what we want to do is cross over those charges into subscripts.

02:46 So the calcium is going to get a two because the oxygen.

02:51 Has a minus 2 charge, and the oxygen gets a 2 because the calcium has a plus 2 charge.

03:05 You're going to take those subscripts now and divide them by the largest common factor.

03:10 So in this case, it's actually 2, because that goes into two divides into both of those numbers.

03:17 So when we divide that out, what we're left with is 1 calcium and 1 oxygen.

03:29 So the formula for that would be c -a -o.

03:37 Let's take the example of potassium sulfide.

03:41 If you break it down into its elements and write those symbols, you have potassium and sulfide.

03:55 And we'll give them charges.

03:56 Potassium has a plus one.

04:03 And you know that by looking at your periodic table.

04:07 And sulfide has a minus two.

04:09 So now what we want to do is cross over those charges into subscripts for each one.

04:21 So this time potassium is going to get a 2 because sulfide has that minus 2 up there.

04:30 And sulfide's going to get a 1 because potassium has that plus 1 up there.

04:40 We're going to figure out what is the largest common factor that divides evenly into both of these numbers.

04:45 In this case, it's a 1.

04:47 So you're going to divide each number by a 1, and that's going to be the formula.

04:52 That you end up with.

04:53 So in this case, we have two potassiums and one sulfide.

05:04 So k2s would be our formula.

05:09 Let's do magnesium chloride.

05:13 If we break it up into its elements, we have an mg.

05:25 I'll just keep scrolling down so it's so it's neater.

05:34 Mg and a cl...

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