(c) Which is most likely to be a gas at room temperature and ordinary atmospheric pressure, F2, Br2, K2O

Video transcript

Welcome back everyone in this example, we need to identify the compound that is most likely to be a gas at room temperature. So we should recall that melting point and boiling point of a substance determined state of matter at room temperature. So, first considering our cl-2 molecule, we should recognize this as our chlorine molecule, which is a di atomic halogen Because we recognize chlorine on our periodic table in group seven a. So looking at our molecule of chlorine, we have two chlorine atoms bonded to one another because we don't have a difference in electro negativity because they are the same atom. This is a covalin bond or a covalin molecule and it's going to be non polar. And so because it's a non polar covalin molecule, we have only the weak inter molecular force present, which is our London dispersion force. And that means that there's a weak attraction between our chlorine molecules and so they won't form a lattice, meaning that there is only a low amount of energy required to break The attractive forces between our cl two molecules. And that's because these attractive forces are weak, as we stated, they're just the London dispersion forces. So we also want to recall that chlorine has a low melting point and a low boiling point. And so because of all of these reasons we've noted above, we would say that therefore Cl two is a gas at room temperature. So at 25 degrees Celsius. So we can already confirm this first molecule, Cl two as a correct choice because it's most likely to exist as a gas at room temperature. Moving on to sodium chloride Next, we should recognize that we have a metal being our sodium atom bonded to a non metal being our chlorine atom and this is based on their position on the periodic table. So this is going to be an ionic compound, meaning we have the presence of the sodium plus one, carry on because it's in group one A. And we have the presence of the cl minus one and ion because it's in group because chlorine is in group seven A on our periodic table. And so our molecule is going to be sodium bonded to a chlorine where we have a slightly positive charge on our sodium atom and a slightly negative charge on our chlorine atom. Because chlorine we recall is more electro negative than sodium. And so we would have a disciple in the direction of our chlorine atom. So this is going to be there for a polar molecule, meaning we have the strong inter molecular force, sorry, inter molecular force of attraction which we recall as our dipole dipole force. So we have this strong electrostatic force between our sodium and chlorine molecules which create a crystalline lattice. And this means that we have a high amount of energy needed at high temperatures. I'm sorry. This is so high amount of energy needed at a high temperature to break these forces between these molecules. We also want to recall that sodium cord has a high boiling point and a high melting point. And so we would say that therefore sodium chloride is a solid at room temperature. So we would rule out sodium chloride because it's most likely just going to be a solid at room temperature. It has high boiling point and a high melting point as well as a strong crystalline lattice between the molecules. And that leaves us with our carbon tetrachloride last. So we'll just draw our molecule. We have a carbon atom surrounded by four chlorine atoms. Let's make that meter. So carbon surrounded by four chlorine atoms. We recognize that chlorine being more electro negative than carbon based on our electro negativity trend will have type holes in all of the directions of our chlorine atoms. However, because we have symmetry in this molecule, meaning we have these four chlorine atoms making up each side of our molecule, this is going to be a non polar molecule, meaning we only have London dispersion forces which we recall our week attractive forces between our molecules of carbon tetrachloride. We also want to recall that carbon tetrachloride has a low melting point and a high boiling point. Let's make sure that that's visible. So it has a low melting point and a high boiling point and because of its high boiling point, it's therefore going to be a liquid at room temperature. So it has a low melting point and high boiling point. So it's a liquid at room temperature it does not form a lattice because it has the week London dispersion forces between the molecules. So we would rule out carbon tetrachloride. And that means that our only correct choice for the compound that is most likely to exist as a gas at room temperature is going to be our chlorine molecule. So I hope that everything I explained was clear. Everything highlighted in yellow is our final answer. And if you have any questions, just leave them down below. So I'll see everyone in the next practice video.