Understanding Ionic Solid Structures

The learning objective of the topic is represent an ionic solid with a particulate model that is consistent with Coulomb's law and the properties of the constituent ions. By now, we already know what is Coulomb's law, but how to represent a model of the ionic solid which would be consistent with Coulomb's law as well as the properties of the ions. We will be seeing all of that in this video. Hello everyone, this is topic. 2.3 structure of ionic solids. This is taken from AP chemistry college board. Let's start. We already know that like charges repel and unlike charges attract each other. Here you can see that there are positively charged ions and negatively charged ions. Four cases are represented and in each case the arrangement of ions is different. In the first case the positively charged ions or cations are arranged alternately and in between them the negatively charged ions or anions are present. In case B you can see that there are layers of the charges. There is one layer which is positively charged then there is another layer which is negatively charged ions and in case C there are two layers of positively charged ions and then there are two layers of negatively charged ions. In case D there is random arrangement of both the ions so if we want to see that which of these cases would be more stable i would say that case a would be more stable arrangement for the ions because here the like charges are separated by another charge that is two positive charges are separated by a negative charge and similarly two negative charges are separated by a positive charge so This arrangement shows that there is an attraction between the positive and negative ions and this makes it very stable. While in case B, these positively charged ions would repel each other. Similarly, these negatively charged ions would also repel each other. Although there is attraction between this positive and this negative, but still the repulsion would be more. And similar is the case C. where there would be repulsion between the like charges. In case D, you can see that there are some places when the like charges are adjacent to each other. So, in such cases, there will be repulsion. That is why the arrangement in the case A would make it very stable. This was the arrangement which we normally see in the ionic solids. And these ions arrange themselves in such a way that the repulsion is minimum. and there is maximum attraction which makes it stable. Here I have taken the case of NaCl. You can see that sodium atom has 11 protons and 11 electrons. It donates one ion and it becomes Na positive ion which is a cation and still it has 11 protons and 10 electrons. This electron is taken up by chlorine atom which has 17 protons and 17 electrons. When this chlorine atom takes up that electron it becomes Cl negative ion and the total number of electrons become 18. So now there is an attraction between these two ions and this attraction leads to this kind of structure which we saw in the previous slide also that how these ions arrange. Here you can see the periodic table of the elements and this is just a recap of what we did in the periodic trends. If you have not seen the video you can click the card above. And here I will just tell you that the size of the atoms goes on increasing as we move down the group because of the increase in the number of shells. And as we move across the period the size of the atoms goes on decreasing. because of the increase in the number of protons which leads to increase in the effective nuclear charge. We will be seeing that how this periodic trend will be affecting the representation of the model of ionic solids. Here I am comparing two ionic solids one is N-ABR and another is RBBR. The common thing between these two compounds is bromine atom. This compound has sodium atom and this compound has rubidium atom. We can see in the periodic table also that sodium and rubidium these two elements are from the same group. And I have already told you that as we move down the size of the atom goes on increasing because of the increase in the number of shells. That is why when we see this structure we can see that the sodium ion is smaller than the bromide ion. And on the other case when we compare the sizes of rubidium and bromide ion. ions we can see that sizes are almost the same. Bromine atom lies here in the periodic table. So when we compare this size with the sodium atom we can see that the sodium atom is smaller than bromine atom. Although when we compare the sizes of bromine and rubidium atoms, rubidium when loses the electron it gets an electronic configuration of krypton. and bromine atom when gains an electron it also gets the electronic configuration of krypton but when we see the sizes bromide ion would be a little bit bigger than the rubidium ion because bromide ion has a negative charge so negatively charged ions are little bit bigger than the positively charged ions now let's see one question here the diagrams below show the structures of two ionic solids sro and the unknown metal MO. So here SRO is shown and here is the arrangement for the MO. Based on the diagrams above and the periodic trends which of the following correctly identifies the metal cation M2 positive. We need to tell the identity of M2 positive ion. So we can see that strontium lies here and when we compare the sizes of strontium and this M2 positive we can see that this strontium is little bit smaller. smaller than M2 positive ion. As we move down the group the size of the ions goes on increasing and when we see the size of magnesium ion it would be smaller. The titanium ion would also be smaller than Sr2 positive as well as Fe2 positive ion would also be smaller than Sr2 positive. That is why the correct option is Ba2 positive. Now let's see this question which of these is ionic structure for KCl. In all these arrangements we can see that the arrangement is like one positive ion then one negative then one positive and then one negative. Just the difference is the size of cation and the anion. So let's see for KCl. K lies here and Cl is here. So when potassium will lose one electron it will have the electronic configuration of argon. and when that electron will be accepted by chlorine atom it will also have the electronic configuration of argon out of both the ions the chloride ion would be a little bit bigger because chloride ion is negatively charged and the potassium ion is positively charged so if we see these four arrangements i would say that case d is the most appropriate because the positive ion is smaller than the negative ion in case c the sizes are almost the same and in case a and b the negative ion is smaller than the positive ion so case d is the correct answer this was about how to represent the particulate model of an ionic solid now let's see what are the properties of ionic solids ionic solids are hard and they have high melting and boiling point So these two properties are because of strong electrostatic attraction between the ions. Another property of ionic solid is brittleness. So brittleness means when you apply some pressure to the solid it would break easily. This is the particulate model of the ionic solid and when this force is applied there is a movement of layers of the ions. So you can see here that when the layers move the positive ion became close to another positive ion. So this leads to repulsion between the like charges and due to this repulsion the crystal cracks or you can say the ionic solid cracks. Another property of ionic solid is it does not conduct electricity in solid state because the ions are fixed at a place they cannot move so that is why they are not a good conductor of electricity in solid state but they are good conductor in liquid and aqueous state because when they change into liquid or aqueous state the ions can move freely and that is why the conductor activity increases. So the learning objective of the topic was represent an ionic solid with a particulate model that is consistent with Coulomb's law and the properties of the constituent ions. So we saw that how can we actually represent the model of an ionic solid with the help of Coulomb's law and we also saw that how that model was consistent with the properties of the ions. Please like and subscribe to the channel LogIota and press the bell icon.

This is taken from AP chemistry college board. Let's start. We already know that like charges repel and unlike charges attract each other.

Here you can see that there are positively charged ions and negatively charged ions. Four cases are represented and in each case the arrangement of ions is different. In the first case the positively charged ions or cations are arranged alternately and in between them the negatively charged ions or anions are present. In case B you can see that there are layers of the charges.

There is one layer which is positively charged then there is another layer which is negatively charged ions and in case C there are two layers of positively charged ions and then there are two layers of negatively charged ions. In case D there is random arrangement of both the ions so if we want to see that which of these cases would be more stable i would say that case a would be more stable arrangement for the ions because here the like charges are separated by another charge that is two positive charges are separated by a negative charge and similarly two negative charges are separated by a positive charge so This arrangement shows that there is an attraction between the positive and negative ions and this makes it very stable. While in case B, these positively charged ions would repel each other. Similarly, these negatively charged ions would also repel each other. Although there is attraction between this positive and this negative, but still the repulsion would be more.

And similar is the case C. where there would be repulsion between the like charges. In case D, you can see that there are some places when the like charges are adjacent to each other.

So, in such cases, there will be repulsion. That is why the arrangement in the case A would make it very stable. This was the arrangement which we normally see in the ionic solids. And these ions arrange themselves in such a way that the repulsion is minimum.

and there is maximum attraction which makes it stable. Here I have taken the case of NaCl. You can see that sodium atom has 11 protons and 11 electrons. It donates one ion and it becomes Na positive ion which is a cation and still it has 11 protons and 10 electrons.

This electron is taken up by chlorine atom which has 17 protons and 17 electrons. When this chlorine atom takes up that electron it becomes Cl negative ion and the total number of electrons become 18. So now there is an attraction between these two ions and this attraction leads to this kind of structure which we saw in the previous slide also that how these ions arrange. Here you can see the periodic table of the elements and this is just a recap of what we did in the periodic trends.

If you have not seen the video you can click the card above. And here I will just tell you that the size of the atoms goes on increasing as we move down the group because of the increase in the number of shells. And as we move across the period the size of the atoms goes on decreasing. because of the increase in the number of protons which leads to increase in the effective nuclear charge.

We will be seeing that how this periodic trend will be affecting the representation of the model of ionic solids. Here I am comparing two ionic solids one is N-ABR and another is RBBR. The common thing between these two compounds is bromine atom. This compound has sodium atom and this compound has rubidium atom.

We can see in the periodic table also that sodium and rubidium these two elements are from the same group. And I have already told you that as we move down the size of the atom goes on increasing because of the increase in the number of shells. That is why when we see this structure we can see that the sodium ion is smaller than the bromide ion. And on the other case when we compare the sizes of rubidium and bromide ion.

ions we can see that sizes are almost the same. Bromine atom lies here in the periodic table. So when we compare this size with the sodium atom we can see that the sodium atom is smaller than bromine atom.

Although when we compare the sizes of bromine and rubidium atoms, rubidium when loses the electron it gets an electronic configuration of krypton. and bromine atom when gains an electron it also gets the electronic configuration of krypton but when we see the sizes bromide ion would be a little bit bigger than the rubidium ion because bromide ion has a negative charge so negatively charged ions are little bit bigger than the positively charged ions now let's see one question here the diagrams below show the structures of two ionic solids sro and the unknown metal MO. So here SRO is shown and here is the arrangement for the MO.

Based on the diagrams above and the periodic trends which of the following correctly identifies the metal cation M2 positive. We need to tell the identity of M2 positive ion. So we can see that strontium lies here and when we compare the sizes of strontium and this M2 positive we can see that this strontium is little bit smaller. smaller than M2 positive ion. As we move down the group the size of the ions goes on increasing and when we see the size of magnesium ion it would be smaller.

The titanium ion would also be smaller than Sr2 positive as well as Fe2 positive ion would also be smaller than Sr2 positive. That is why the correct option is Ba2 positive. Now let's see this question which of these is ionic structure for KCl.

In all these arrangements we can see that the arrangement is like one positive ion then one negative then one positive and then one negative. Just the difference is the size of cation and the anion. So let's see for KCl.

K lies here and Cl is here. So when potassium will lose one electron it will have the electronic configuration of argon. and when that electron will be accepted by chlorine atom it will also have the electronic configuration of argon out of both the ions the chloride ion would be a little bit bigger because chloride ion is negatively charged and the potassium ion is positively charged so if we see these four arrangements i would say that case d is the most appropriate because the positive ion is smaller than the negative ion in case c the sizes are almost the same and in case a and b the negative ion is smaller than the positive ion so case d is the correct answer this was about how to represent the particulate model of an ionic solid now let's see what are the properties of ionic solids ionic solids are hard and they have high melting and boiling point So these two properties are because of strong electrostatic attraction between the ions. Another property of ionic solid is brittleness.

So brittleness means when you apply some pressure to the solid it would break easily. This is the particulate model of the ionic solid and when this force is applied there is a movement of layers of the ions. So you can see here that when the layers move the positive ion became close to another positive ion.

So this leads to repulsion between the like charges and due to this repulsion the crystal cracks or you can say the ionic solid cracks. Another property of ionic solid is it does not conduct electricity in solid state because the ions are fixed at a place they cannot move so that is why they are not a good conductor of electricity in solid state but they are good conductor in liquid and aqueous state because when they change into liquid or aqueous state the ions can move freely and that is why the conductor activity increases. So the learning objective of the topic was represent an ionic solid with a particulate model that is consistent with Coulomb's law and the properties of the constituent ions. So we saw that how can we actually represent the model of an ionic solid with the help of Coulomb's law and we also saw that how that model was consistent with the properties of the ions.

Please like and subscribe to the channel LogIota and press the bell icon.

Transcript for:Understanding Ionic Solid Structures

Transcript for:
Understanding Ionic Solid Structures