Atoms, Ions, and the Periodic Table

Questions and Answers

How is the neutron number (N) calculated?

N is equal to the atomic mass minus the atomic number (correct)

N is equal to atomic number plus orbital electrons

N is the sum of protons and electrons

N is equal to the number of nucleons in the atom

What does the atomic number (Z) represent in an atom?

The number of electrons in a positively charged ion

The combined number of protons and neutrons

The total number of neutrons in the atom

The number of protons in the atom (correct)

What is true about elements within the same group in the periodic table?

They all have the same atomic mass

They are all metals

They possess identical chemical properties

They have similar outer-shell electron configurations (correct)

Which of the following correctly characterizes a nucleon?

It can be either a proton or a neutron Signup and view all the answers

What does the standard atomic notation indicate?

It summarizes the atomic and nuclear composition Signup and view all the answers

Which is a characteristic of the periodic table?

The table includes both natural and man-made elements Signup and view all the answers

What does the term 'nucleon' not refer to?

Electrons Signup and view all the answers

What distinguishes elements' symbols in the periodic table?

Some symbols originate from the Latin names of the elements Signup and view all the answers

What is the approximate neutron to proton ratio for heavy elements?

N ≈ 1.5 Z Signup and view all the answers

What mainly contributes to the instability of very heavy nuclei?

A high number of identical particles in a confined space Signup and view all the answers

Which type of force do neutrons provide in nuclear stability?

Only exchange forces Signup and view all the answers

Why do heavier elements require more neutrons?

To compensate for long-range repulsive coulombic forces Signup and view all the answers

Where do stable nuclides appear on a graph of neutron versus proton numbers?

Along an imaginary line called the line of stability Signup and view all the answers

What happens to nuclides that are not close to the line of stability?

They undergo decay Signup and view all the answers

What is the significance of the number 209Bi in relation to nuclear stability?

It marks the end of the line of stability Signup and view all the answers

Which factor primarily affects the stability of light elements?

A roughly equal number of neutrons and protons Signup and view all the answers

What is a positron also referred to as?

Positive beta particle Signup and view all the answers

In positron decay, what is emitted as a result of the annihilation reaction?

Annihilation photons Signup and view all the answers

What happens to the kinetic energy of a positron after it is ejected from the nucleus?

It is lost in collisions with surrounding atoms Signup and view all the answers

What process competes with positron decay?

Electron capture Signup and view all the answers

What is the lifetime of positronium, the temporary interaction between a positron and an electron?

Approximately 10 seconds Signup and view all the answers

What is the mass-energy equivalent of each particle involved in the annihilation reaction?

0.511 MeV Signup and view all the answers

Which shells do electrons typically come from during the electron capture process?

K and L shells Signup and view all the answers

During electron capture, what type of radiation is emitted as a result of the energy lost by an outer-shell electron?

Characteristic X-rays Signup and view all the answers

What is the physical half-life of a radionuclide?

The time required for it to decay to 50% of its initial activity level Signup and view all the answers

How is the decay constant (λ) related to the half-life (𝑇₁/₂)?

λ = 0.693 / 𝑇₁/₂ Signup and view all the answers

What does the decay factor (DF) represent?

The fraction of radioactive atoms remaining after a time t Signup and view all the answers

What happens to the number of radioactive atoms and activity over time due to exponential decay?

They both decrease proportionally Signup and view all the answers

Which mathematical expression represents the number of radioactive atoms over time?

N(t) = N e^λt Signup and view all the answers

What does the term 'exponential decay' imply about the radioactive atoms in a sample?

Their activity decreases rapidly initially then levels off Signup and view all the answers

Why is it important to know how to determine decay factors when working with radionuclides?

To understand the remaining quantity of radioactive material Signup and view all the answers

Which statement is true regarding the detection of a radioactive sample?

Detection occurs through the analysis of radiation emitted during disintegration Signup and view all the answers

What distinguishes gamma rays from X-rays?

Gamma rays originate from processes within the nucleus. Signup and view all the answers

Which correctly describes a conversion electron?

It results from excess energy transferred to an inner-shell electron. Signup and view all the answers

How does beta-minus (β−) emission affect the atomic number of a radionuclide?

It increases the atomic number by transforming a neutron into a proton. Signup and view all the answers

Which type of decay typically transforms a proton-deficient radionuclide towards stability?

Beta-minus (β−) decay Signup and view all the answers

What is a characteristic of even-even nuclei regarding stability?

They are more stable due to the pairing of alike particles. Signup and view all the answers

Which decay mode moves the nucleus closer to the line of stability when proton deficient?

Beta-minus (β−) emission Signup and view all the answers

Why do heavy nuclides often decay by alpha emission or fission?

To reduce their mass number effectively. Signup and view all the answers

What happens after an outer-shell electron falls into an inner orbital following internal conversion?

X-ray photon is released. Signup and view all the answers

Study Notes

Subatomic Particles: Atoms vs. Ions

Nucleons include protons and neutrons.
The atomic number (Z) represents the number of protons and equals the number of electrons in a neutral atom.
Neutron number (N) is calculated as A - Z, where A is the atomic mass.

Standard Atomic Notation

Summarizes atomic and nuclear composition using a chemical symbol and an elemental symbol.

Periodic Table

Organizes all known elements, both natural and synthetic, by atomic number.
Elements arranged in columns (groups) and rows (periods) exhibit similar properties due to comparable outer electron counts.
Symbols may derive from English or original Latin names; for example, gold (Au) and mercury (Hg).
Heavy elements typically have about 50% more neutrons than protons (N ≈ 1.5 Z).

Stability in Atomic Systems

Large groups of identical particles in confined spaces tend to be unstable, especially in heavy nuclei.
Light elements prefer a near-equal neutron-proton ratio for stability, while heavier elements may require more neutrons to balance repulsive forces among protons.

Line of Stability

Stable nuclides cluster around an imaginary line on a neutron vs. proton graph.
Stability requires more neutrons to stabilize larger proton counts, with the line of stability ending at bismuth-209 (Z = 83, N = 126).
Radionuclides away from this line are typically unstable.

Positron Decay

A positron (β+) is an antiparticle of an electron and emitted from unstable nuclei.
Positronium is formed as positrons pair with electrons before annihilating into two 0.511 MeV photons.

Electron Capture

Inner orbital electrons can be captured by a nucleus, turning protons into neutrons.
This process results in characteristic X-rays or Auger electrons from energy released when outer-shell electrons fill vacancies.

X-rays vs. Gamma Rays

X-rays originate from electron processes outside the nucleus; gamma rays are emitted from the nucleus post-radioactive decay.
Gamma rays possess higher energy than X-rays.

Internal Conversion

Excess energy in excited nuclei can eject an orbital electron, creating a conversion electron.
The vacancy left is filled by an outer-shell electron, emitting energy as X-rays or Auger electrons.

Decay Notation

Paths of decay indicate changes in atomic number, where leftward paths (EC, β+) decrease atomic number and rightward paths (β−) increase it.
Heavy nuclides typically decay via α emission or fission for mass reduction.

Physical Half-life

Represents the time needed for a radionuclide to decay to 50% of its initial activity.
Related to the decay constant through the formula: ( T_{1/2} = \frac{0.693}{\lambda} ).

Exponential Decay

The number of radioactive atoms decreases over time, reflected in reduced activity.
Decay equations express this relationship mathematically as:
- ( N(t) = N_0 e^{-\lambda t} )
- ( A(t) = A_0 e^{-\lambda t} )
- Where ( \lambda = \frac{0.693}{T_{1/2}} ).

Decay Factor

The decay factor represents the fraction of radioactive atoms remaining after a set time, displaying an exponential approach towards zero.

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Description

Explore the fundamentals of subatomic particles, including the roles of protons, neutrons, and electrons. Understand standard atomic notation and how elements are organized in the periodic table based on atomic number and properties. This quiz will help reinforce your knowledge of atomic structure and stability in atomic systems.