key term - Atomic Nuclei

Definition

The atomic nucleus is the dense, central core of an atom, which contains the protons and neutrons that make up the atom's mass. It is the defining feature of an atom, as the number of protons in the nucleus determines the element's identity and chemical properties.

5 Must Know Facts For Your Next Test

1. The strong nuclear force is the force that holds the protons and neutrons together within the atomic nucleus.
2. The mass of the atomic nucleus is nearly the entire mass of the atom, as the electrons contribute very little to the overall mass.
3. The size of the atomic nucleus is extremely small compared to the overall size of the atom, with the nucleus taking up only a tiny fraction of the atom's volume.
4. Radioactive atoms have unstable nuclei that undergo spontaneous decay, emitting particles or energy in the form of radiation.
5. The number of protons in the nucleus determines the element, while the number of neutrons can vary, creating different isotopes of the same element.

Review Questions

• Explain the role of the strong nuclear force in holding the atomic nucleus together.
  • The strong nuclear force is the fundamental force that holds the protons and neutrons together within the atomic nucleus. This force is incredibly strong, overcoming the repulsive electrical force between the positively charged protons, and is what gives the nucleus its stability. Without the strong nuclear force, the protons would repel each other, and the nucleus would fly apart. The strength of this force is what allows the nucleus to maintain its dense, compact structure, which is essential for the atom's overall stability and chemical properties.
• Describe how the number of protons and neutrons in the nucleus affects the characteristics of an atom.
  • The number of protons in the nucleus determines the element, as each element has a unique number of protons that defines its identity and chemical properties. The number of neutrons, however, can vary, creating different isotopes of the same element. Isotopes have the same number of protons but a different number of neutrons, which affects the mass and stability of the nucleus. Stable isotopes have a balanced ratio of protons and neutrons, while unstable isotopes, or radioactive atoms, have an imbalance that can lead to spontaneous nuclear decay and the emission of particles or energy in the form of radiation.
• Analyze the relationship between the size of the atomic nucleus and the overall size of the atom.
  • The atomic nucleus, despite containing the vast majority of the atom's mass, occupies an incredibly small fraction of the atom's overall volume. This is because the nucleus is extremely dense and compact, with the protons and neutrons packed tightly together by the strong nuclear force. In contrast, the electrons orbiting the nucleus take up a much larger volume, even though they contribute very little to the atom's total mass. This disparity in size between the nucleus and the surrounding electron cloud is a key feature of the atomic structure, and it highlights the fact that atoms are mostly empty space, with the nucleus accounting for only a tiny portion of the atom's overall size.

Related terms

Protons:

Positively charged subatomic particles that reside in the nucleus of an atom and determine the element's identity.

Neutrons:

Electrically neutral subatomic particles that, along with protons, make up the nucleus of an atom.

Isotopes:

Atoms of the same element that have the same number of protons but a different number of neutrons in their nuclei.