Читать книгу Foundations of Chemistry - Philippa B. Cranwell - Страница 71

The original organisation of elements in the periodic table was proposed by Mendeleev in 1869. This was before experiments had been carried out that proved the existence of atomic orbitals and energy levels in atoms. He organised the elements based on their atomic masses and other properties. It is now known that chemical reactivity depends upon electronic structure, so our current periodic table agrees with Mendeleev's. The periodic table consists of four main areas, which are generally shown shaded in different colours.

On the left hand of the periodic table are Groups 1 and 2. The elements in these groups are known as s block elements as their highest energy electrons are in s orbitals.

On the right of the periodic table are the p block elements. These constitute the elements in Groups 3–8 (or Groups 13–18) where the p orbitals are being filled.

In the middle section are the d block elements. This area includes 10 groups of elements from Sc to Zn in the first row of the d block. These elements are all metals and those in Groups 3-11 are often referred to as transition elements. The elements in the group headed by zinc (Group 12) are not transition elements.

At the bottom of the periodic table are the two rows of elements that form the f block. The elements in these two rows are called the lanthanides and actinides and have electrons filling the f orbitals. In total, f orbitals can hold 14 electrons, as there are 7f orbitals. A discussion of these orbitals is beyond the scope of this book.