Summary Atomic Nucleus - General Chemistry for MCAT

Introduction

nuclear reactions are changes that occur in an atom's nucleus, altering its number of protons and/or neutrons and often transforming one element into another. These reactions release radiation and can happen without visible signs.

The Essence of Nuclear Reactions

Nuclear reactions change an atom's identity by changing its atomic number (proton count). The exact moment a single nucleus decays is unpredictable, but by observing many nuclei together scientists can measure an average decay time.

Types of Nuclear Decay

• Alpha decay: the nucleus emits an alpha particle (two protons and two neutrons), producing a different nucleus.
• Beta decay: a neutron transforms into a proton, increasing the atomic number and changing the element.
• Gamma decay: the nucleus releases a high-energy photon (gamma ray) while its composition stays the same; gamma rays are highly penetrating and can be harmful but have practical uses in medicine.

Key Concepts

• Isotopes: atoms of the same element with different numbers of neutrons; isotopes differ in mass and stability and can undergo different types of decay.
• Randomness of decay: the timing of decay for a single nucleus is arbitrary, though average rates are measurable across many nuclei.
• Cosmic radiation: space exposes astronauts to high-energy radiation (gamma rays), which is a significant risk on long missions and requires protective measures.