Predicting and identifying reactions and products Revision Notes

The Periodic Table and Reactivity Trends

The Periodic Table organises elements based on their atomic number and electron configurations. Elements in the same vertical column, called a group, share similar chemical properties because they have the same number of outer shell electrons. These outer electrons are crucial for chemical reactions. We can use an element's position to predict its likely reactivity and the types of reactions it will undergo. Generally, metals are found on the left and in the middle of the Periodic Table, while non-metals are on the right. Metalloids, with properties of both, are found along the diagonal line separating metals and non-metals.

Reactivity of Metals (Groups 1 and 2)

For metals in Groups 1 (alkali metals) and 2 (alkaline earth metals), reactivity increases as you move down the group. This trend is due to the atomic structure. As you go down a group, atoms have more electron shells. This means the outermost electrons, which are involved in reactions, are further away from the positively charged nucleus and are shielded by more inner electron shells. This greater distance and shielding reduce the electrostatic attraction between the nucleus and the outer electrons, making it easier for the atom to lose these electrons. Since metallic reactivity is often about losing electrons, the easier it is to lose them, the more reactive the metal.

Reactivity of Non-metals (Group 17 Halogens)

For non-metals, specifically Group 17 (the halogens), reactivity shows the opposite trend: it decreases as you move down the group. Halogens react by gaining an electron to achieve a full outer shell. As you go down Group 17, the atoms become larger and have more electron shells. The increased distance between the nucleus and the outer shell, along with increased shielding by inner electrons, means the attraction for an incoming electron to fill the outer shell is weaker. Therefore, it becomes harder for larger halogen atoms to attract and gain an electron, making them less reactive than smaller halogens higher up in the group.

Unreactive Elements (Group 18 Noble Gases)

Group 18 elements, known as the noble gases, are characterised by their extreme unreactivity. This is because they already possess a full outer shell of electrons (a duet for helium, and an octet for others). Having a full outer shell makes these elements very stable and eliminates the need for them to gain, lose, or share electrons to form chemical bonds. Consequently, noble gases do not readily participate in chemical reactions, which is why they are often used in situations where an inert atmosphere is required, such as in light bulbs or welding.

Specification Link

This particle-level chemistry diagram is used for: Retrieve and apply knowledge of the general properties of transition metals and their compounds and exemplify these by reference to a small number of transition metals.

What To Explain

A good answer links the diagram to particles, bonding or molecular interactions that explain the chemical behaviour.

Exam Answer Move

The mapped objective is: Retrieve and apply knowledge of the general properties of transition metals and their compounds and exemplify these by reference to a small number of transition metals. The answer should give a particle-level or molecular explanation.

Specification Link

This particle-level chemistry diagram is used for: Retrieve and apply knowledge of the general properties of transition metals and their compounds and exemplify these by reference to a small number of transition metals.

What To Explain

A good answer links the diagram to particles, bonding or molecular interactions that explain the chemical behaviour.

Exam Answer Move

The mapped objective is: Retrieve and apply knowledge of the general properties of transition metals and their compounds and exemplify these by reference to a small number of transition metals. The answer should give a particle-level or molecular explanation.

Specification Link

This particle-level chemistry diagram is used for: Retrieve and apply knowledge of the general properties of transition metals and their compounds and exemplify these by reference to a small number of transition metals.

What To Explain

A good answer links the diagram to particles, bonding or molecular interactions that explain the chemical behaviour.

Exam Answer Move

The mapped objective is: Retrieve and apply knowledge of the general properties of transition metals and their compounds and exemplify these by reference to a small number of transition metals. The answer should give a particle-level or molecular explanation.