Atomic Nuclei, Radioactivity, and Chemical Bonding

Atomic Nucleus and the Nature of Radioactivity

The nucleus is the small central core of an atom, containing a positive electric charge and the majority of the atom's mass. It is made up of nucleons (protons and neutrons) bound together by the strong nuclear force. This force is stronger than the electromagnetic force between the nucleus and electrons, but it only works over very short distances. The nucleus does not intervene in chemical changes.

Radioactive Decay and Radioisotopes

Some atoms, whether naturally occurring or artificial elements, have particular combinations of protons and neutrons that make them unstable. These atoms decompose by emitting energetic radiation and changing the nucleus. This process is known as radioactive decay, and these unstable atoms are called radioisotopes.

Radioactive decay is a random process, but it has statistical properties such as half-life. There are three kinds of radioactive emissions:

• Alpha: Beams of energetic helium nuclei.
• Beta: Beams of fast electrons.
• Gamma: High-energy electromagnetic radiation.

Radiation is dangerous; it can kill body cells. Large doses cause radiation sickness, while small doses over long periods can cause cancer.

Practical Applications of Radioisotopes

Radioisotopes are highly useful in various fields:

• Engineering: Checking oil and gas pipes for leaks by adding radioisotopes to the oil or gas. Radiation is detected with instruments like the Geiger counter.
• Radiotherapy: Isotopes can cure cancer because the rays given out on decay will kill cancer cells.
• Dating: Radioisotopes are used to find the age of old remains.

Chemical Bonding and Atomic Stability

Noble gases are different from other elements; they do not form compounds and are unreactive and stable, existing as single atoms. A full outer shell brings stability. By reacting with each other, atoms obtain a full outer shell and become stable.

Types of Chemical Bonds

Chemical bonds are the forces acting between atoms in a compound. Atoms bond in different ways to gain full outer shells:

• Ionic bonding: Giving or accepting electrons.
• Covalent bonding: Sharing electrons.
• Metallic bonding: Outer shell electrons are free to move in a "sea of electrons."

The type of bonding depends on the number of valence electrons an atom has. Metals have a small number of valence electrons, which they lose easily to reach a full shell, transferring electrons to non-metals to form ionic compounds or clustering with other metal atoms via metallic bonds. Non-metals have a higher number of valence electrons and easily gain them to reach a full shell. This electron supply comes from metals in ionic compounds. They can also reach a full shell by sharing electrons with another non-metal to form molecules with covalent bonds or giant covalent structures.

Ionic Bonding and Electrostatic Forces

When metals and non-metals react together, they form ionic compounds. The metal loses electrons to become a cation, and the non-metal gains them to become an anion. Each ion is surrounded by the maximum number of ions of opposite charge that their size ratio allows, and a giant 3D structure is formed.

An ionic bond is the strong electrostatic force that holds ions together. The force between two ions is proportional to the product of their charges and inversely proportional to the square of the distance by which they are separated.