IGCSE Chemistry - Group VII Properties

Objective

Predict the properties of other elements in Group VII, given information about the elements.

Properties of Group VII Elements

Group VII elements (also known as the Halogens) are located in Group 7 of the periodic table. They are highly reactive non-metals.

Trends in Properties

The properties of Group VII elements show clear trends as you move down the group:

• Atomic Radius: Increases down the group.
• Ionization Energy: Decreases down the group.
• Electronegativity: Decreases down the group.
• Reactivity: Decreases down the group.

Explanation of Trends

Atomic Radius: The number of electron shells increases down the group, leading to a larger atomic radius.

Ionization Energy: It requires less energy to remove an electron from a larger atom with more electron shells. Therefore, ionization energy decreases down the group.

Electronegativity: The attraction for electrons decreases down the group as the nucleus is further away and shielded by more inner electrons. Hence, electronegativity decreases down the group.

Reactivity: Reactivity refers to the tendency to gain an electron to achieve a stable octet. As electronegativity decreases down the group, the tendency to gain electrons also decreases, leading to lower reactivity.

Reactivity of Group VII Elements

Group VII elements are highly reactive, with reactivity decreasing down the group. The most reactive element is Fluorine (F₂), and the least reactive is Astatine (At). This is because the ability to gain an electron decreases down the group.

Chemical Reactions of Group VII Elements

Group VII elements readily react with metals to form salts (e.g., Sodium Chloride - NaCl). They also react with hydrogen to form hydrogen halides (e.g., Hydrogen Chloride - HCl).

Predicting Properties of Other Group VII Elements

Based on the trends discussed above, we can predict the properties of other Group VII elements:

Examples

Fluorine (F):

• Smallest atomic radius in Group VII.
• Highest ionization energy and electronegativity.
• Most reactive halogen.
• Exists as a diatomic gas (F₂).

Chlorine (Cl):

• Intermediate atomic radius, ionization energy, and electronegativity.
• Highly reactive, but less so than Fluorine.
• Exists as a diatomic gas (Cl₂).

Bromine (Br):

• Larger atomic radius, lower ionization energy, and lower electronegativity than Chlorine.
• Less reactive than Chlorine.
• Exists as a liquid at room temperature.

Iodine (I):

• Even larger atomic radius, lower ionization energy, and lower electronegativity than Bromine.
• Least reactive halogen.
• Exists as a solid at room temperature.

Astatine (At):

• Largest atomic radius, lowest ionization energy, and lowest electronegativity.
• Very little reactivity.
• Radioactive and rare.

Table of Group VII Elements and their Properties

Element	Symbol	Atomic Number	State at Room Temperature	Colour	Reactivity	Electronegativity	Ionization Energy (kJ/mol)
Fluorine	F	9	Gas	Pale Yellow	Very High	4.0	1412
Chlorine	Cl	17	Gas	Green	High	3.1	1214
Bromine	Br	35	Liquid	Reddish-Brown	Moderate	2.6	1900
Iodine	I	53	Solid	Dark Purple/Black	Low	2.1	1640
Astatine	At	85	Solid (Radioactive)		Very Low	2.0	1021