Group VII Properties | Chemistry for Grade 11 (IGCSE) PDF Download

Group VII Properties & Trends

The halogens

• Group VII Non-Metals: Fluorine, chlorine, bromine, iodine, and astatine are part of this group. They are toxic in nature.
• Diatomic Nature: Halogens exist as diatomic molecules, meaning they combine to form molecules of two atoms. The halogens' formulas are: F₂, Cl₂, Br₂, I₂, and At₂.
• Electrons in Outer Shell: All halogens possess seven electrons in their outer shell.
• Formation of Halide Ions: Halogens create halide ions by gaining an additional electron to achieve a full outer shell.
• Limited School Experiments: Due to its hazardous nature, fluorine is typically avoided in school experiments, focusing on chlorine, bromine, and iodine instead.

Properties of the halogens

• At room temperature (20°C), the physical state of the halogens changes as you go down the group.
• Chlorine is a pale yellow-green gas, bromine is a red-brown liquid, and iodine is a grey-black solid.
• This demonstrates that the density of the halogens increases as you go down the group.
• The Physical State of the Halogens at Room Temperature:

• Reactivity of Group VII non-metals increases as you go up the group (this is the opposite trend to that of Group I).
• Each outer shell contains seven electrons, and when the halogen reacts, it will need to gain one outer electron to get a full outer shell of electrons.
• As you go up Group VII, the number of shells of electrons decreases (period number decreases moving up the Periodic Table).
• This means that the outer electrons are closer to the nucleus, so there are stronger electrostatic forces of attraction, which help to attract the extra electron needed.
• This allows an electron to be attracted more readily, so the higher up the element is in Group VII, the more reactive it is.
• Diagram showing the electronic configuration of the first three elements in Group VII:
  

Predicting Group VII Properties

• You may receive details about certain elements and have to anticipate the traits of other elements in the same group.
• The provided information may relate to melting/boiling points or physical state/density, making it crucial to understand the trends within the group.

Melting and boiling point

• The melting and boiling points of halogens increase as you move down the group.
• Fluorine, positioned at the top of Group VII, exhibits the lowest melting and boiling points.
• Conversely, astatine, located at the bottom of Group VII, showcases the highest melting and boiling points.

Physical states

• The halogens' density increases down the group.
• Fluorine, positioned at the top of Group VII, exists as a gas.
• Astatine, found at the bottom of Group VII, is in a solid state.

Colour

• As you descend the group, the halogens' color darkens.
• Fluorine, being at the top of Group VII, appears yellow due to its lighter color.
• Astatine, situated at the bottom of Group VII, displays a darker color and appears black.