A vacancy is a: Group of answer choices a. point defect in which an extra atom is occupying space not normally occupied in the crystal. b. point defect in which an atom is missing from a lattice site in the crystal. c. twisting defect caused by the application of a shear force. d. linear defect that centers on the line that is defined along the end of the extra half-plane of atoms.

b. point defect in which an atom is missing from a lattice site in the crystal.

Explanation:

A vacancy is a point defect in which atom is missing in crystal and because of this irregular crystal lattice is formed.

Point defects are of different types:

Self interstitial

Substitution impurity

Interstitial impurity

Vacancy

It is the point defect in which an extra atom occupy interstitial void. They are occur in very low concentration.

It is the type of defect in which another atom comes and occupy the position of atom of bulk. The size of impurity atom is approximately equal to the bulk atom.

In interstitial impurity a smaller atoms occupy the space in the lattice not in the place of atoms of bulk. It means smaller atom fit into the vacant space between the atoms.

It is the type of defect in which atom is missing. It means vacancy is created in place of atom. It is mostly occur at temperature when kinetic energy increased and atoms escape from its position and randomly move thus changed their position and create empty space.

it is to be noted that an alpha particle is an helium nucleus. so it contains 2 protons 2 neutrons and has a mass number of 4. when alpha decay particles are ejected from the nucleus it gets transformed into an atom which has atomic number less than 2 and a mass number less than 4.

an equation that could represent alpha decay is radium 226 decay of alpha particle forms radon 222.

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