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Naming ions and ionic compounds

Ionic compounds are neutral compounds made up of positively charged ions called cations and negatively charged ions called anions. For binary ionic compounds (ionic compounds that contain only two types of elements), the compounds are named by writing the name of the cation first followed by the name of the anion. For example, KCl, an ionic compound that contains K⁺ and Cl⁻ ions, is named potassium chloride.

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  • leaf green style avatar for user Dennis Chamberlin
    At ...
    "...the chlorine grabs an electron..."
    What is this "grab"? Both the chlorine and the potassium were initially neutral, where the positive protons and negative electrons balanced each other and seemed happy. What is it that propels the electron over to Chlorine? It wouldn't seem to be an electrical force.
    (68 votes)
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    • female robot grace style avatar for user Nirlipta Pande
      If you see the electronic configuration of Cl you will observe that it is just one electron short of a noble gas configuration which is the ultimate 'happy' state. Similar is the case for K which has 1 electron in excess so K gives its excess electron to Cl, both achieve a stable noble gas configuration and they live happily ever after. :D
      In short the desire to achieve stability propels the atoms to lose,gain or share electrons
      (150 votes)
  • leaf green style avatar for user Ankit Kumar Singh
    why is chlorine ion named as chloride? Just because it is halide? What about potassium?
    (15 votes)
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  • aqualine ultimate style avatar for user Alex
    What does the K mean for potassium
    (13 votes)
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  • aqualine seed style avatar for user Rebekah  B.
    I am having trouble getting this concept of ionic compounds. When I go to the practice section on this it asks me questions like, " What is the most stable monatomic ion formed from fluorine?" I am not seeing in the video on how to solve these problems. Maybe it is just me? Thank you! :)
    (22 votes)
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    • female robot grace style avatar for user Selena
      The most stable monatomic ion will occur when the atom's electron shells are all completely full. For example, fluorine will want 1 more electron to fill it's electron shell because it's one away from the closest noble gas. Thus, by adding one electron, it would become F-
      (8 votes)
  • ohnoes default style avatar for user Shelton
    When K wants to give up an electron because it has 1 too many and Cl takes the electron because it wants to become like a noble gas...wouldn't they immediately break apart after the electron transfer is complete?
    (6 votes)
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  • starky seed style avatar for user Hannah
    Why is potassium chloride considered an "ionic" compound if the two atoms already neutralized each other?
    (8 votes)
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  • winston default style avatar for user The Kiyomo's
    Alkali metals in Group one like to lose an electron and Halides like to have one more electron to have 8 electrons in the outer shell, so that they are more stable.
    However, why is this configuration the most stable one? What makes it stable?
    (6 votes)
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  • blobby green style avatar for user arshia
    why does potassium go by "K" in the periodic table?
    (1 vote)
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    • leaf red style avatar for user Richard
      The symbol for potassium, K, comes from the Arabic kali, which comes from the root word alkali, al-qalyah in Arabic, which means plant ashes.

      In 1807, British chemist Humphry Davy isolated potassium by electrolysis and named it potassium which derived from the earlier name of pot ash (he added the –ium suffix because it’s a metal). The name potassium itself goes back to original Arabic meaning and the original way of obtaining potassium. The idea is that you would take plant ashes, like wood, and dissolve the water soluble potassium compounds in water in a pot, hence the name pot ash. The water solution with potassium compounds is slightly basic, which also explains the connection of alkali and basicity. The actual potassium salts are obtained by allowing the water to evaporate which leaves behind the salt.

      In 1809 German chemist Ludwig Wilhelm Gilbert proposed the name Kalium as an alternative to Davy’s which was more in line with in earlier German chemist, Martin Klaprot, who proposed the name kali in 1797, again in reference to alkali. Nowadays English and French speaking countries primarily use potassium for the name, while other countries including Germany use kalium. The IUPAC allows both names, but chose K for the symbol in reference to the German kalium name.

      Hope that helps.
      (11 votes)
  • duskpin ultimate style avatar for user Lillian Z.
    Does this naming system work for all ionic compounds?
    I'm confused about when exactly you would keep the cation name and add the -ide to the anion element. Is it only for ionic compounds with a metal, like potassium?
    (4 votes)
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    • piceratops seed style avatar for user RogerP
      It does get more complicated than this and it takes an entire book to cover all the rules. But in simple terms, when an element such as potassium forms a cation (K+) then it is still called potassium - there is no change of name. It is the atoms that form the anions that change names, so chlorine becomes chloride (Cl-). Hence the ionic compound formed between potassium and chlorine is called potassium chloride.

      But not all anions end in "ide". If there is oxygen involved as well, then they end in "ite" or "ate". For example, sodium sulfate (Na2SO4, made of Na+ and SO4^2- ions).
      (5 votes)
  • duskpin tree style avatar for user SunnyWolf
    When the halogens are mentioned, it seems like they are characterized by having 7 electrons. My question is... do all atoms with an odd number of electrons "want" an even number of electrons? In , Sal says that the halogens would love to have 8 electrons.

    Also, how does Sal get 7 electrons in the first place? For a neutral atom (if it is one), I thought there would be, for example, 17 electrons for Chlorine.

    I think I'm missing something. I'd appreciate it if someone would help me :)
    (3 votes)
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    • leaf red style avatar for user Richard
      The other replier is correct; Sal is referring to valence electrons. Yes, an atom like chlorine has more than seven electrons, but only the valence electrons are responsible for chemical bonding and so we’re only interested in those (as opposed to the core electrons).

      An atom like chlorine prefers to have eight valence electrons, not so much because eight is an even number, but rather because it is trying to follow the octet rule. The octet rule is a general rule which says that many elements achieve stability by having eight valence electrons. There are atoms with even valence electrons as neutral atoms, and not eight (like oxygen), which also try to achieve eight valence electrons following this octet rule.

      Hope that helps.
      (6 votes)

Video transcript

- [Instructor] Let's get some practice now thinking about how ions typically form, how they might form compounds and how we name those compounds. So let's start with something in group one. In this first column, this first column is often known as alkali metals. So let's start with potassium. K is the symbol for potassium. Now things in group one here, one way to think about is their outermost shell has one electron in it. So they wouldn't mind losing that electron. So when they ionize, they tend to lose an electron and become a cation, a positive ion. And so let's look at a situation where I have some potassium that has been ionized. I could write it just like this, we've seen that in previous videos and we can refer to this just as a potassium ion, we could refer to this as potassium one plus. We could refer to this as a potassium cation. Now let's go on to the other side of the periodic table. Things that would really love to grab an electron. So things in group, in the halides, which is this column right over here. So these are the halides. They have seven electrons in their outermost shell. They would love to have eight, so they tend to be really good at grabbing electrons. And so let's say we're dealing with chlorine, and chlorine is able to ionize. So it's able to grab an electron. When chlorine grabs an electron, it will be a negatively charged ion, so you could write it as Chlorine one minus, but the way that we generally refer to an anion, a negatively charged ion, instead of just calling this the chlorine anion, we would call this chloride. So this we would refer to as Chloride. Now as you can imagine with potassium having a positive one charge or one plus charge and this having a negative charge, they're going to be attracted to each other and they can actually form an ionic compound. The ionic compound they would form, we would write as, you'd write your positive ion first and then you would write your negative ion. And this right over here would be described as potassium chloride. Let me write that down. Potassium, potassium chloride. Now you might be saying, "Well, I just," Let me rewrite the whole thing. So you know the chloride part, you say okay, this is going to be an anion because instead of writing chlorine which is the name of this element, I wrote this IDE at the end to say, "Hey, this is an anion," so I know that this is the chlorine anion, this is chloride, why didn't I do something similar for potassium? Well, the way the convention works is if someone says potassium chloride, you know you're dealing with an ionic compound and if the chlorine has a negative one charge, an ionic compound, the whole thing is gonna be neutral. So if this one over here is one minus, then you know this over here is just one-for-one, this is going to be one plus so you know that you're dealing with a potassium cation and you could say and a chloride ion or a chlorine anion. You could refer to it various ways, but this is potassium chloride. You have a positively charged potassium and you have a negatively charged chlorine, which we would call a chloride. In the next few videos I'll do many, many more examples of this and ones that will be a little bit more complicated.