Group Properties

Group Properties Overview

• In the Periodic Table, elements are arranged according to their atomic number, which increases from left to right.
• Within the table, there are vertical columns known as groups. There are eight main groups.
• Elements in the same group have similar chemical properties because they have the same number of electrons in their outermost shell.

Trends Within a Group

• As we descend a group (going down), the number of energy levels (shells) of electrons increases.
• This increase in energy levels leads to an increase in atomic radius because the electrons are further from the nucleus and are less strongly attracted.
• There is also an increase in the number of inner electrons which gives rise to more shielding, reducing the attraction between the electrons and the nucleus.
• Metallic character increases down a group due to the increase in atomic size and the decrease in ionisation energy.
• Non-metallic character decreases down a group because the attraction between the nucleus and the outer electron is weaker due to increased distance and shielding.
• Reactivity increases for metals as we descend a group due to the ease in losing electrons and forming positive ions.
• Reactivity decreases for non-metals down a group due to the increased difficulty in gaining electrons and forming negative ions.

Group 1 - Alkali Metals

• Group 1 metals are also known as the alkali metals and include lithium, sodium, and potassium.
• They have one electron in their outer shell, which is lost easily; thus, they are highly reactive.
• Reactivity increases down the group; for instance, potassium is much more reactive than lithium.
• Alkali metals react readily with water to form alkalis and hydrogen gas.

Group 7 - Halogens

• Group 7 elements are called the halogens and include fluorine, chlorine, and iodine.
• Halogens have seven electrons in their outer shell and tend to gain an electron to achieve a full outer shell; therefore, they are all reactive non-metals.
• Halogens are poorer conductors of electricity than metals as they usually gain electrons rather than lose them.
• Reactivity decreases down the group, with fluorine being the most reactive and iodine being the least reactive among the common halogens.

Group 0 - Noble Gases

• Group 0, also known as Group 8 or the noble gases, includes helium, neon, and argon.
• They are not reactive due to having a full outer shell of electrons.
• As a result, they do not readily form compounds and exist as single atoms. Because of this, they are described as monatomic.
• The boiling and melting points of noble gases increase down the group due to an increase in van der Waals forces.