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Halogens - Concept

Teacher/Instructor Jacqueline Spivey
Jacqueline Spivey

Ph.D.,U.C.Santa Cruz
Teaching at a top-ranked high school in SF

She teaches general and chemistry at a top-ranked high school in San Francisco. Prior to that, she lead and published a number of research studies and lectured at SF State University.

Halogens are nonmetal elements located on the right side of the periodic table in Group 7. Halogens include the elements of flourine, chlorine, bromine, iodine and astatine. Halogens have a negative 1 charge and are considered very reactive.

Let's continue talking about the periodic table and delve a little further in and talk specifically about group 7a or the halogens which are located right here next between the oxygen family and next to the noble gases.

So, as you can see here they're in pink so they are non-metals and so some of the typical characteristics of non-metals they display which are melting and boiling points increasing with increasing atomic number.

So let's talk about a few of the elements that are contained in this family. So fluorine and chlorine are gases at room temperature, bromine is a liquid at room temperature and iodine is a solid at room temperature. And part of the probably most important part of halogens that you're going to encounter is that they all exist as what we call diatomic atoms. Okay that means you've got F2, Cl2, Br2 and I2. And that's because halogens are very reactive. So they only need one electron to achieve an octet. So remember when you were doing electron configurations and you are writing out your s and your p and your d orbitals? Okay, so these guys have their s orbital field so two electrons in there and they also have five electrons in their p orbitals. So they just need one electron in order to gain to gain the octet to become like the noble gases and they're very interested in doing that. So, in order to keep them from reacting with everything, they bond covalently with each other. So again, chlorine will bond to a chlorine, fluorine will bond to a fluorine, bromine to a bromine, iodine to an iodine.

So, they also have highly negative electrons affinities. And so that they'll readily become anions which is the negative form of themselves. Right, so fluorine will become a minus, chlorine a minus, bromine a minus and iodine a minus because that indicates that they've gained the electron that they needed to fill their octet and that makes them more stable.

So, more specifically, fluorine is the most electronegative atom on the periodic table. So it can remove an electron from almost any substance, it really really really wants that extra electron.

Chlorine however is one of the most industrially useful element in this family and it's something with which we're all super familiar. It reacts slowly to form stable aqueous solutions so this equation at the bottom here was water reacting with chlorine gas to form hydrochloric acid and hypochlorus acid. This is a common reaction for the disinfectants that we use to put into our pools and that we sometimes see in our water to keep things clean. And that is halogens.