Question

How do the forces that hold an atomic nucleus together compare in strength with the forces between atoms in a molecule?

Short answer

The strong nuclear force that holds an atomic nucleus (protons and neutrons) together is much stronger (about \(10^2\) to \(10^3\) times) than the electromagnetic forces (covalent, ionic, and hydrogen bonds) that act between atoms in a molecule. However, the strong nuclear force has a very short range (1-2 fm), making it effective only at very small distances, while the electromagnetic force dominates over longer distances.

Step-by-step solution

Identify the forces in an atomic nucleus

The main force that holds an atomic nucleus (composed of protons and neutrons) together is known as the strong nuclear force. This force acts between nucleons (protons and neutrons) in the nucleus and holds them together despite the repulsion between the positively charged protons due to the electromagnetic force (Coulomb repulsion).

Relate the forces in an atomic nucleus

The strong nuclear force is much stronger than the electromagnetic force on the scale of the nucleus. However, this force acts over a very short range (around 1-2 fm, where \(1 fm = 10^{-15}\,m\)). Due to this short range, the strong force is effective only at very small distances and loses its strength rapidly as the distance between nucleons increases. This is why the electromagnetic force dominates over longer distances, and the nuclei become unstable when the number of protons and neutrons is not balanced.

Identify the forces between atoms in a molecule

The forces between atoms in a molecule are mainly due to the electromagnetic force. These forces can be attractive or repulsive, depending on the charges on atoms and the distance between them. The major attractive forces in a molecule are: 1. Covalent bonds formed by the sharing of electrons between atoms 2. Ionic bonds formed by the electrostatic attraction between oppositely charged ions 3. Hydrogen bonding or van der Waals forces, which are weaker than covalent and ionic bonds but still significant

Compare the magnitudes of the forces

The magnitude of the strong nuclear force is of the order of \(10^2\) to \(10^3\) times stronger than the electromagnetic force. Therefore, it is much stronger than the forces acting between atoms in a molecule, such as the covalent, ionic, and hydrogen bonds. These intermolecular forces are relatively weak compared to the strong nuclear force that holds the nucleus together. In conclusion, the forces that hold an atomic nucleus together, mainly the strong nuclear force, are much stronger than the forces between atoms in a molecule. However, the strong nuclear force acts over a very short range, whereas the electromagnetic force dominates over longer distances.

Key concepts

Electromagnetic Force

The electromagnetic force is one of the fundamental forces in physics, responsible for interactions between charged particles. It plays a crucial role in holding atoms and molecules together. The force arises from the interactions between electric charges, whether static or in motion, like electrons orbiting a nucleus.

• **Origins:** Electromagnetic force originates from the electric charges of particles. Opposite charges attract each other, while like charges repel each other.
• **Range and Effects:** It extends over infinite ranges, albeit decreasing with distance, and is responsible for phenomena like electricity, magnetism, and light.
• **In Everyday Life:** This force is vital in chemical bonding like covalent and ionic bonds in molecules, bringing together atoms to form vast arrays of structures and substances around us.

In molecular contexts, static electric charges create attractions leading to bonds such as ionic and covalent. The electrons' movements result in dynamic electromagnetic forces that hold molecules intact.

Atomic Nucleus

The atomic nucleus is the dense, positively charged core of an atom. It's made up of protons and neutrons, which are collectively known as nucleons.

• **Components:** The number of protons defines the element, while neutrons can vary, leading to different isotopes.
• **Strong Nuclear Force:** Inside the nucleus, the strong nuclear force holds nucleons together, overcoming the electromagnetic repulsion between positively charged protons.
• **Stability Issues:** This force is incredibly potent over short distances (up to a few femtometers), yet its short range means that as nuclei grow larger, they can become unstable without enough neutrons to balance electron repulsion among protons.

The stability of an atomic nucleus is crucial for its integrity. It's especially important in heavier elements where the balance of forces can determine whether a nucleus will remain intact or undergo radioactive decay.

Intermolecular Forces

Intermolecular forces are the forces between molecules that influence the physical properties of substances. Unlike the forces holding together a nucleus, these forces are primarily electromagnetic in nature and exist over larger ranges.

• **Types of Interactions:** Key forms of intermolecular attractions include hydrogen bonding, dipole-dipole interactions, and van der Waals forces.
• **Strength and Impacts:** Compared to nuclear forces, intermolecular forces are significantly weaker. However, they still play critical roles in determining melting and boiling points, solubilities, and other physical states of matter.
• **Applications:** For example, hydrogen bonds are responsible for water's high boiling point and ice's less dense structure, which allows it to float.

Understanding these forces allows chemists and physicists to predict substance behavior under various conditions, from gaseous diffusion to the formation of solid lattices.