Basic Nuclear Physics - Atomic Structure

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Questions and Answers

What is the defining characteristic of a stable or non-radioactive nuclide?

Its atoms do not decay. (correct)

Its atoms undergo radioactive transformation.

Its atomic number is greater than its neutron number.

Its neutron number is less than its atomic number.

What is the general relationship between neutron number and atomic number for the heaviest stable nuclei?

N is twice Z.

N is about 1.5 times Z. (correct)

N is equal to Z.

N is less than Z.

What holds the nucleus together despite the positively charged protons' tendency to repel each other?

Nuclear force. (correct)

Weak nuclear force.

Electromagnetic force.

Gravitational force.

What is the process by which radionuclides emit particles to adjust their neutron to proton ratio?

Radioactive transformation. Signup and view all the answers

Which of the following is NOT a naturally occurring radionuclide?

192Ir. Signup and view all the answers

What is the purpose of 99mTc in medicine?

Diagnostic imaging. Signup and view all the answers

What is the general term for nuclei that do not fall on the line of stability?

Radionuclides. Signup and view all the answers

What is the force that overcomes the positively charged protons' tendency to repel each other in stable nuclei?

Nuclear force. Signup and view all the answers

What is the charge of an electron in an atom?

Negative Signup and view all the answers

What determines the identity of an element and its atomic mass?

Protons and neutrons Signup and view all the answers

What is unique about the number of protons in an element?

It is unique for each element Signup and view all the answers

What is the composition of an atom?

Protons, neutrons, and electrons Signup and view all the answers

What is the function of the nucleus in an atom?

To determine the identity of the element and its atomic mass Signup and view all the answers

What is the charge of a neutron?

No charge Signup and view all the answers

What is the atomic number of oxygen?

8 Signup and view all the answers

What determines the nuclear stability of an atom?

The ratio of protons to neutrons Signup and view all the answers

What is a unique property of neutrons?

They carry no electrical charge Signup and view all the answers

What is the primary function of electrons in atoms?

To share or exchange with other atoms to form chemical bonds Signup and view all the answers

What is the arrangement of electrons around the nucleus of an atom?

In discrete shells Signup and view all the answers

What determines the maximum number of electrons in each shell?

A fixed number for each shell (e.g., 2 in K shell, 8 in L shell) Signup and view all the answers

What is the charge of an electron?

-1 Signup and view all the answers

What is the difference in mass between a neutron and a proton?

The neutron is slightly heavier than the proton Signup and view all the answers

What is the symbol for a neutron?

n Signup and view all the answers

What is the energy of a proton in MeV?

938.2 Signup and view all the answers

What is the approximate mass of an electron in grams?

9.1094 x 10-28 grams Signup and view all the answers

What determines the element of an atom?

The number of protons in the nucleus Signup and view all the answers

In an uncharged atom, what is the relationship between the number of electrons and protons?

The number of electrons is equal to the number of protons Signup and view all the answers

What is the most abundant element in the Earth's mass?

Oxygen Signup and view all the answers

What is the atomic number of Calcium?

20 Signup and view all the answers

What is the term for atoms of the same element with different numbers of neutrons?

Isotopes Signup and view all the answers

What is the typical notation for isotopes?

A Xy Signup and view all the answers

What is the general relationship between the number of protons and neutrons in most isotopes?

Most isotopes have more neutrons than protons Signup and view all the answers

Study Notes

Basic Atomic Structure

An atom is composed of three main particles: positively charged protons, uncharged neutrons, and negatively charged electrons.
The nucleus of an atom consists of protons and neutrons, which determines the identity of the element and its atomic mass.

Protons

Protons are positively charged particles found inside the nucleus of an atom.
Each element has a unique atomic number, which is the number of protons in an atom.
The proton number never changes for a given element.

Neutrons

Neutrons are particles found in the nucleus of an atom with no electrical charge, making them "neutral".
Atoms of a given element do not always contain the same number of neutrons.

Electrons

Electrons are negatively charged particles that surround the nucleus in "orbits" similar to moons orbiting a planet.
The sharing or exchange of electrons between atoms forms chemical bonds, which is how new molecules and compounds are formed.

Electron Binding Energy

Electrons exist in discrete "shells" around the nucleus, with each shell representing a unique binding energy holding the electron to the nucleus.
The shells are designated by letters (K, L, M, N …), where K, the shell closest to the nucleus, has the largest binding energy.
The maximum number of electrons in each shell is 2 in K shell, 8 in L shell, and so on.

Atomic Mass Unit (amu)

The atomic mass of the proton and the neutron is approximately 1.0073 amu and 1.0087 amu, respectively.
The atomic mass of the electron is approximately 0.00055 amu, which is much smaller than that of the proton or neutron.

Elements

The number of protons in an atom dictates the element, and for an uncharged atom, the number of electrons equals the number of protons.

Isotopes

Atoms of an element that have a different number of neutrons in the nucleus are called isotopes of each other.
Isotope notation is typically written as: A Xy, where A is the atomic mass (neutron + protons) and Xy is the element symbol.

Nuclear Stability

A stable or non-radioactive nuclide is one whose atoms do not decay.
The graph of neutron number N vs atomic number Z for the stable nuclei shows an interesting pattern.
For the heaviest stable nuclei, N is about 1.5 times Z.

Unstable Nuclei

Nuclei that do not fall on the line of stability tend to be unstable or "radioactive".
They are called "radionuclides".
Radionuclides undergo a process called radioactive transformation or disintegration to adjust their neutron to proton ratio.

Some Common Radionuclides

Examples of radionuclides include naturally occurring 235U and 238U, 60Co, 137Cs, 90Sr found in nuclear power plants, 192Ir used in radiography, 99mTc used in nuclear medicine, and 131I used in the treatment of thyroid conditions.

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Description

Understand the basics of atomic structure, including neutrons, protons, and electrons, and learn about atomic number, atomic mass, and nuclear stability.