Atomic Number (Z): The number of protons present in the
nucleus of an atom of an element is called the atomic number.
Atomic number (Z) = Number of protons = Number of electrons
Atomic Mass Number (A): The total number of
protons and neutrons present in the nucleus of an atom of an element is
called the atomic mass number.
Atomic mass number (A) = Atomic number (Z) + Neutron number (N)
Neutron Number (N): The number of neutrons present in the
nucleus of an atom of an isotope of an element is called the neutron number.
N = A - Z
Isotopes:The atoms of the same
element, which differ in the number of neutrons present in the nuclei of
their atoms are called isotopes.
The atoms of the same element having the same atomic
number, but different atomic mass number are called isotopes.
Isobars: The atoms of different elements, which have
the same atomic mass number, but different atomic numbers, are called
Nuclear Forces: The strong attractive forces
which exists between the protons and neutrons present in the nucleus
of an atom are called nuclear forces.
Mass Defect Dm: The difference between
the total mass of the nucleons (protons and neutrons) present in the nucleus
of an atom and the actual mass of the nucleus is called the mass defect of
Binding Energy (B.E.): The amount of energy required to
break the nucleus of an atom into its constituent nucleons is called binding
energy of the nucleus.
Radioactivity: The phenomenon of spontaneous
disintegration of an unstable nuclei of certain
heavy elements with the emission of some radioactive radiation is called
Disintegration Law:The number of atoms
disintegrated per unit time is a constant fraction of the total number of the
atoms present at that instant.
Decay or Disintegration Constant (l):The fraction of the
total number of atoms (nuclei) undergoing radioactive disintegration per unit
time is called decay or disintegration constant of the element.
Half-life Period (t1/2): The time required
for the disintegration of a radioactive element to reduce to half of the
original amount is called half-life period.
Artificial Transmutation: The process of
conversion of a stable isotope of one element into a stable isotope of
another element by bombarding it with suitable high energy (nuclear)
particles is called artificial transmutation.
Target:The atomic nucleus that
is bombarded by high energy nuclear particles (projectiles) is called a
The high energy nuclear particle such as a-particle, proton or neutron, which is used
to bombard an isotope of an element, is called a projectile.
Product or Recoil Nucleus: The new atom
produced from the target nucleus after it is bombarded with projectiles and
which has mass number not very different from that of the target is known as
product or recoil nucleus.
Emissions: The particles which are ejected from a
target nucleus after bombardment with projectiles are called emissions.
Natural Radioactivity: The spontaneous emission of radiation
from the nuclei of a heavy element is called natural radioactivity.
Artificial Radioactivity: The phenomenon of
conversion of a stable nucleus (non-radioactive) into an unstable radioactive
nucleus by artificial disintegration is called artificial radioactivity.
Nuclear Fission: The process of splitting of a heavy nucleus
into two or more nuclei of lighter atoms is called nuclear fission.
Nuclear Fusion: The process in which two light nuclei
combine to form heavier, stable nuclei, with the liberation of a large amount
Radioisotopes:The naturally unstable
elements, which spontaneously emit radiations like a-particles, protons,
neutrons, g-rays, etc. are
called as radioisotopes.