Positively-charged particles consisting of two protons and two neutrons emitted by radioactive materials is called

Alpha particle

Explanation:

Alpha decay is defined as the decay process in which a heavier nucleus decays into a lighter nuclei. This decay process releases alpha particle which is also known as helium nucleus.

Alpha particle released carries a mass of 4 units and a charge of +2 units. The alpha particle is also known as helium atom.

In this decay, the atomic number of the atom released gets reduced by 2 units and atomic mass is reduced by 4 units as helium contains 2 protons and 2 neutrons as atomic number is 2 and mass number is 4.

The chemical equation for the alpha decay process is given as:

Alpha particle

Explanation:

luster is not a good characteristic to use by itself because luster is the property of minerals that indicates how much the surface of a mineral reflects light. the luster of a mineral is affected by the brilliance of the light used to observe the mineral surface.

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explanation: