Natural Radioactivity

These flashcards cover key concepts related to natural radioactivity, including decay mechanisms, stability factors, and properties of radioactive nuclides.

The process that produces nuclides that can be stable or unstable is called __.

Nucleogenesis

Unstable nuclei decay through a range of mechanisms involving the release of high-energy particles or __.

γ – radiation

The four most important radioactive decay mechanisms are alpha decay, beta decay, __, and __.

positron emission, electron capture

In alpha decay, an alpha particle is simply a __ nucleus with a mass of 4 and charge of 2+.

helium

An example of a nucleus undergoing alpha decay is __.

uranium-238

During alpha decay, the uranium atom (238U92) is transmuted into __ (234Th90).

thorium

The symbol for an alpha particle is __.

4He2

In beta decay, a neutron is converted into a __.

proton

The emission of β (or β-) refers to an __ ejected from the nucleus.

electron

In positron emission, when a positron (β+) is ejected, it usually collides with __.

an electron

The mass number assigned to an electron is __.

zero (0)

The atomic number assigned to an electron is __.

-1

The nuclear symbol representing a beta particle is __.

0β-1

Thorium-234 undergoes beta decay to form __ (91Pa234).

protactinium

Gamma rays frequently accompany nuclear reactions and are produced in the decay of __.

U-238

Factors that determine whether a nucleus is stable or unstable include the size of the nucleus and the __ ratio.

proton: neutron (N/P)

Stable nuclides lie within the __ zone.

zone of stability

The rule for nuclear stability indicates that unstable isotopes must decay towards the __.

zone of stability

Nuclei decay via beta emission produce __ particles and cause radiation damage.

high-energy

The nuclear decay series involves radioactive elements such as __ and actinides.

lanthanides

Radiation damage can be caused by __ emitted during electron capture.

x-rays

The beta decay of nuclei requires an atomic number and mass number assigned to an __.

electron

Beta decay results in the emission of a __ particle from the nucleus.

beta

A radioactive decay sequence can be represented as a graph of atomic number versus __ number.

neutron

Primary radio nuclides are long-lived and formed during the process of __.

nucleogenesis

Most primary radio nuclides possess very long __ periods.

half-life

The isotopic abundance of primary radio nuclides is sometimes below __.

1%.

The existence of long-lived primary radio nuclides progressively changes the isotopic composition and hence the __ of parent and daughter elements.

atomic weight

One characteristic of the decay of primordial radio nuclides is that they are considered __ in their isotopic composition.

stable

An instability in a nucleus often results in the need for __ to reach stability.

decay

Alpha decay typically results in a __ of two protons and two neutrons.

decrease

Beta decay involves a __ of one neutron and an increase of one proton.

decrease

For stable elements, the N:Z ratio is approximately __ but favors more neutrons as the nucleus increases in size.

1

Among radioactive isotopes, those that decay toward stability include wife-elements found in the period of their __.

development