Basic Nuclear Physics: Atomic Structure

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Questions and Answers

What is a unique characteristic of neutrons?

They have a negative charge

They have a positive charge

They have no electrical charge (correct)

They have a varying charge

What is the purpose of electrons in atoms?

To repel other electrons

To attract other atoms

To form chemical bonds with other atoms (correct)

To provide structure to the nucleus

What determines the binding energy of electrons?

The shell they occupy (correct)

The number of electrons in the atom

The mass of the nucleus

The distance from the nucleus

What is the maximum number of electrons in the K shell?

2 Signup and view all the answers

What is the approximate mass of a proton in grams?

1.6726 x 10^-24 grams Signup and view all the answers

Which of the following is NOT a characteristic of neutrons?

They have a negative charge Signup and view all the answers

What is the symbol for an electron?

e Signup and view all the answers

What is the binding energy of an electron in the K shell?

Highest in the atom Signup and view all the answers

What is the charge of an electron?

Negatively charged Signup and view all the answers

What is the function of the nucleus in an atom?

To identify the element and its atomic mass Signup and view all the answers

What does the atomic number of an element represent?

The number of protons in an atom Signup and view all the answers

What is the main difference between protons and neutrons?

Protons are positively charged, while neutrons are uncharged Signup and view all the answers

What is the role of electrons in an atom?

To orbit the nucleus Signup and view all the answers

What is the name of the model that describes the atom as having a small, heavy nucleus surrounded by electrons?

Rutherford's Model Signup and view all the answers

What is the term for atoms that have the same atomic number but different atomic masses?

Isotopes Signup and view all the answers

What is the charge of a proton?

Positively charged 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

How many times smaller is the electron compared to the proton or neutron?

What determines the element of an atom?

The number of protons Signup and view all the answers

What is the relationship between the number of protons and electrons in an uncharged atom?

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

Which element has the largest percentage of Earth's mass?

Oxygen Signup and view all the answers

What is the term for atoms of an element that have a different number 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 neutrons and protons in isotopes?

Isotopes have more neutrons than protons Signup and view all the answers

What is a stable nuclide?

A nuclide whose atoms do not decay Signup and view all the answers

What is the pattern observed when plotting stable nuclei?

A curve with N>Z Signup and view all the answers

What is the role of extra neutrons in the heaviest stable nuclei?

To overcome the repulsive force of protons Signup and view all the answers

What is the force that holds the nucleus together?

Nuclear force Signup and view all the answers

What is the term for nuclei that are not stable?

Radionuclides Signup and view all the answers

What happens to radionuclides during radioactive transformation?

They emit particles to adjust their N to Z ratio Signup and view all the answers

What is the purpose of radioactive transformation in radionuclides?

To move towards the line of stability Signup and view all the answers

What is an example of a naturally occurring radionuclide?

235U Signup and view all the answers

Study Notes

Basic Atomic Structure

The atom is composed of positively charged protons, uncharged neutrons, and negatively charged electrons.

Atomic Structure Models

Thomson's model, Rutherford's model, and Bohr's model are three different models that describe the structure of the atom.

Nucleus

The nucleus is composed of protons and neutrons, which determines the identity of the element and its atomic mass.
Protons have a positive charge, while neutrons have no charge.

Protons

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

Neutrons

Neutrons are uncharged particles found in the nucleus of an atom.
Atoms of a given element do not always have the same number of neutrons.

Electrons

Electrons are negatively charged particles that surround the nucleus in "orbits".
The sharing or exchange of electrons between atoms forms chemical bonds.

Electron Binding Energy

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

Atomic Mass Unit (amu)

The atomic mass of the proton and neutron is approximately 1 amu.
The atomic mass of the electron is approximately 0.00055 amu, which is much smaller than the proton or neutron.

Elements

The number of protons in an atom determines the element.
For an uncharged atom, the number of electrons equals the number of protons.

Isotopes

Atoms of an element with a different number of neutrons in the nucleus are called isotopes of each other.
Isotopes are typically written as A Xy, where A is the atomic mass (neutron + protons) and Z is the atomic number (protons).
Isotopes can have more neutrons than protons, and some are stable while others are unstable (radioactive).

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 stable nuclei shows a pattern where N is about 1.5 times Z for the heaviest stable nuclei.
The presence of extra neutrons overcomes the positively charged protons' tendency to repel each other and disrupt the nucleus.

Unstable Nuclei

Nuclei that do not fall on the line of stability tend to be unstable or "radioactive" and are called radionuclides.
Radionuclides undergo radioactive transformation or disintegration, emitting particles to adjust their neutron to proton ratio.
This process tends to move the radionuclide towards the line of stability.

Examples of Radionuclides

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

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Description

This quiz covers the basics of atomic structure, including the neutron, proton, and electron, as well as atomic number, atomic mass, and nuclear stability. Learn about the structure of the atom and radioactive nuclei.