Question Video: Determining How the Atomic Radius and Reactivity of the Halogens Change with Increasing Atomic Number | Nagwa Question Video: Determining How the Atomic Radius and Reactivity of the Halogens Change with Increasing Atomic Number | Nagwa

Question Video: Determining How the Atomic Radius and Reactivity of the Halogens Change with Increasing Atomic Number Science • Second Year of Preparatory School

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As the atomic number of the halogen increases, what happens to its atomic radius and reactivity?

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Video Transcript

As the atomic number of the halogen increases, what happens to its atomic radius and reactivity?

We are asked about two properties, atomic radius and reactivity, of the halogens. Let’s have a closer look at the halogen group. The halogens include the elements fluorine, chlorine, bromine, iodine, and astatine. The halogens can be found in group 17 of the periodic table. The group number is the vertical column on the periodic table. Each of the halogens is in a different period on the periodic table, which is the horizontal row.

Elements in the same group number all have the same number of outer-shell electrons. Elements in the same period have the same number of energy levels that contain electrons. So as we go down the halogen group, each halogen has one more energy level than the last. With more energy levels, the atomic radius increases. As we go down the group, the atomic number also increases. Therefore, the atomic radius increases with atomic number.

Let’s have a closer look at the reactivity of the halogens. We will use fluorine to see how halogens generally react. With seven outer-shell electrons, halogens often react by gaining one new electron. When this occurs, a halide ion is formed. A halide ion is formed when a single halogen atom has gained one electron to become an anion with a one minus net charge. Generally, it is easier for halogens to gain one electron with a smaller atomic radius. This occurs due to reasons that are outside the scope of this video. Therefore, reactivity is greater for halogens with a smaller atomic radius. Reactivity thus decreases with increasing atomic number.

So as the atomic number of the halogen increases, the atomic size increases and the reactivity decreases.

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