Question

In a nuclear equation, both the atomic number and the __________ number must be conserved.

Short answer

In a nuclear equation, both the atomic number and the \(mass\) number must be conserved.

Step-by-step solution

Recall the Conservation Laws in Nuclear Reactions

In nuclear reactions, there are two important quantities that are conserved. These are the atomic number (also known as the proton number) and the mass number. The atomic number is represented by Z and the mass number is represented by A.

Identify the Missing Term

Given the information about conservation laws in nuclear reactions, the missing term in the statement is the "mass" number. Both the atomic number (proton number) and the mass number (protons + neutrons) must be conserved in a nuclear equation. So, the complete statement is: "In a nuclear equation, both the atomic number and the mass number must be conserved."

Key concepts

Conservation Laws in Nuclear Reactions

In nuclear physics, conservation laws play a vital role in understanding how nuclear reactions work.
These laws ensure that certain quantities remain unchanged throughout these reactions, providing a foundation for accurately predicting the outcome of nuclear processes.
In nuclear reactions, especially, two key features are conserved:

• Atomic Number (Z)
• Mass Number (A)

Conservation of these quantities means that during any nuclear reaction, the total atomic number and mass number on the reactant side must equal the total atomic number and mass number on the product side.
Think of it like a balanced scale. No matter how the weights on each side change, the total weight must remain constant. This principle helps scientists understand how different elements can transform into one another through nuclear reactions.

Understanding Atomic Number (Z)

The atomic number, represented by the symbol Z, is crucial in identifying elements.
It denotes the number of protons in an atom's nucleus, which determines the element's identity. For example, an atom with 6 protons is always carbon, while 7 protons correspond to nitrogen.

• The atomic number defines the position of an element on the periodic table, as each element has a unique number of protons.
• In nuclear reactions, the atomic number of the products must equal the atomic number of the reactants to fulfill conservation laws.

This ensures elements can be accurately tracked as they undergo nuclear transformations.
For instance, in a nuclear equation depicting uranium-235 decay, the sum of atomic numbers before and after the reaction remains constant to maintain balance.

Exploring Mass Number (A)

Mass number, denoted by A, represents the total number of protons and neutrons in an atomic nucleus.
While the atomic number gives the identity of an element, the mass number provides information about the isotope of that element.
Isotopes are variants of an element that have the same number of protons but different numbers of neutrons.

• For instance, carbon-12 and carbon-14 are isotopes of carbon with mass numbers 12 and 14, respectively.
• In any nuclear reaction, the total mass number must be conserved, meaning the sum of protons and neutrons remains the same before and after the reaction.

This is why the bread-and-butter of checking nuclear equations involves ensuring both the mass number and the atomic number are balanced.
Through understanding and applying these concepts, predicting nuclear reactions becomes systematic and reliable.