The Periodic Table: Understanding the Mysterious Absence of Element 117

The periodic table is a fundamental tool in chemistry, helping us understand the properties and behavior of elements. However, despite its importance, many people have noticed a curious absence - element 117, which should theoretically exist based on our understanding of atomic structure, is nowhere to be found.

But why is this? The reason lies in the way we define elements and their properties. In order to understand this, let's take a closer look at the periodic table and its various components.

Atomic Mass vs Atomic Number

The two most commonly used methods for describing elements are atomic number (Z) and atomic mass (A). Atomic number is simply the number of protons in an atom's nucleus, while atomic mass is the total number of protons and neutrons. While these values may seem similar, they have distinct differences.

For instance, element 117 should theoretically have an atomic mass of around 350 amu (atomic mass units) based on its atomic number. However, despite numerous attempts to synthesize this element, it has yet to be discovered.

Why is hafnium so expensive? The answer lies in the fact that it's extremely difficult to separate from zirconium, another element with similar chemical properties. This makes it a rare and costly material.

But why do elements get more dense as you move towards the center of the periodic table? This phenomenon can be attributed to the way electrons are arranged within atoms. As you move across the table, each new element adds an electron to its outermost energy level, which causes the atomic radius to decrease.

In contrast, if we compare the size of neutral atoms and ions in the periodic table, it becomes clear that there is no straightforward trend in terms of size. This is because electrons shells have no solid surfaces and can be difficult to measure accurately.

Estimating Atomic Size

One way scientists estimate atomic size is by examining the distance between centers of atoms in pure substances using electron microscopes. For example, in diamond, carbon nuclei are approximately 154 picometers apart, which suggests that each carbon atom has a diameter of around 77 pm.

However, mass does follow a more predictable pattern across the periodic table. As atomic number increases, so too does mass, primarily due to the addition of protons and neutrons within the atom.

In conclusion, while element 117 remains elusive, our understanding of atomic structure and properties can help us better understand its absence from the periodic table. By examining the relationships between atomic number, atomic mass, and size, we can gain valuable insights into the behavior of elements and their interactions with each other.

References:

* 'The Elements' by John Emsley

* 'Atomic Properties' by Royal Society of Chemistry

* 'Periodic Table' by Wikipedia

Periodic table with molar mass pdf