Mechanical twinning occurs in metals having body center cubic and hexagonal closed packed structures. Twinning is said to occur when a portion of a crystal takes up an orientation that is related to the orientation of the untwinned lattice in a definite symmetrical manner.
Answer :
The atomic mass is the sum of the number of protons and neutrons in the nucleus of an atom.
Explanation :
Atomic number : it is defined as the number of protons or number of electrons.
Atomic number = number of protons = number of electrons
Mass number or atomic mass : It is defined as the sum of the number of protons and the number of neutrons.
Mass number or atomic mass = Number of protons + Number of neutrons
For example :
Number of protons in carbon = 6
Number of neutrons in carbon = 6
Mass number or atomic mass = Number of protons + Number of neutrons
Mass number or atomic mass = 6 + 6
Mass number or atomic mass = 12
Thus, the atomic mass is the sum of the number of protons and neutrons in the nucleus of an atom.
