![]() ![]() Because of this, they experience stronger van der Waals forces, decreasing their volatility. As you move down the group, the atoms get larger and so have more electrons. Once again, this is all thanks to van der Waals forces. From the data above, it is easy to see that the volatility of the halogens decreases as you move down the group. Volatility is very closely related to melting and boiling points - it is the ease with which a substance evaporates. These require more energy to overcome and so increase the element's melting and boiling points. Because of this, they experience stronger van der Waals forces between molecules. ![]() This is because the atoms get larger and have more electrons. Melting and boiling pointsĪs you can tell from their states of matter shown in the table earlier on, melting and boiling points increase as you go down the halogen group. Notice how chlorine is a larger atom than fluorine. Fluorine and chlorine, shown with their electron configurations. Fluorine has just two main electron shells, whilst chlorine has three. For example, fluorine has the electron configuration 1s2 2s2 2p5, and chlorine has the electron configuration 1s2 2s2 2p6 3s2 3p5. This is because they each have one more electron shell. The physical appearance of the first four halogens at room temperatureĪs you move down the group in the periodic table, the halogens increase in atomic radius. Unlike most groups in the periodic table, the halogens can exist in all three states of matter (gas, liquid, and solid) at room temperature. The halogens have characteristic colours: fluorine is a pale yellow gas, chlorine is a green gas, bromine is a dark red liquid that forms a red-brown vapour, and iodine is a grey-black solid that forms a purple vapour. ![]() However, I can provide a description of the halogens' distinct colours and states at room temperature. They have low melting and boiling points. They show many of the physical properties typical of non-metals.They are poor conductors of heat and electricity.When solid, they are dull and brittle. In the following sections, we'll take a closer look at some of these shared properties. Despite their differences, the halogens share many characteristics. It's so radioactive that it hasn't been possible to collect a pure sample of it. Astatine, in particular, is highly unstable and has a short half-life of just over eight hours, so its properties are mostly hypothetical. Some scientists consider tennessine (Ts) to be a sixth halogen, but we won't be discussing it much because it shows some unusual behaviours, such as not forming negative ions, and because it is extremely unstable and costly to study. The halogen group is made up of five elements: fluorine (F), chlorine (Cl), bromine (Br), iodine (I), and astatine (At). The halogens, shown in the periodic table highlighted in blue ![]()
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