Inorganic Chemistry: The Periodic Table

Understanding the Periodic Table

The Periodic Table is a systematic arrangement of elements, organised based on their atomic number, electron configuration, and recurring chemical properties.
Elements in the same group (vertical column) have similar chemical and physical properties since they have the same number of valence electrons.
Elements in the same period (horizontal row) have their outermost electrons in the same shell level.
Atomic number, denoted by ‘Z’, represents the number of protons in an atom. It is unique to each element and increases in a regular manner across the periods of the periodic table.

Periodicity refers to the recurring trends in physical and chemical properties of elements across periods or groups on the periodic table.
For example, ionization energy, the energy required to remove an electron from an atom, generally increases across a period from left to right and decreases down a group.
Another example is electron affinity, the energy released when an electron is added to an atom, which also generally increases across a period but decreases down a group.

Transition metals are elements found in groups 3-12 of the periodic table, possessing high melting points, high densities, and the ability to form coloured compounds.
These metals are noted for their variable oxidation states and their ability to form complex ions.
Common examples of transition metals include iron, copper, and nickel.

Noble gases, consisting of helium, neon, argon, krypton, xenon, and radon, have full electron shells and are found in Group 18.
These gases are colourless, odourless, and tasteless, and are renowned for their low reactivity due to their stable electron configurations.
They have several uses, including filling balloons (helium), providing the glow in neon lights (neon), and being used in medical imaging (xenon).

Alkali metals (Group 1) and alkaline earth metals (Group 2) are highly reactive metals, with alkali metals being more reactive than alkaline earth metals.
Alkali metals only have one electron in their outermost energy level, leading to a strong tendency to lose this electron, while alkaline earth metals have two electrons in their outermost energy level.
Alkali metals react vigorously with water, while alkaline earth metals react less vigorously.

Halogens (Group 17) are non-metals that need one more electron to attain a stable noble gas configuration, leading them to be very reactive.
As you move down the group, the reactivity decreases - for example, Fluorine is the most reactive, while Iodine is much less so.
Halogens exist as diatomic molecules in their natural state (e.g., Cl2, Br2) and they display a range of physical states at room temperature (e.g., gas (Fluorine, Chlorine), liquid (Bromine), solid(Iodine, Astatine)).

The periodic table can be used to predict the chemical properties of an element based on its position.
For example, elements in the same group will tend to form ions with the same charge, and elements in the same period will have the same number of electron shells.
Additionally, elements on the left of the periodic table (metals) will typically lose electrons to form positive ions, while those on the right (non-metals) will typically gain electrons to form negative ions.