which of the following is the best defintion of an atom

Question

shane_b · Answer

What are the options?

anonymous · Answer

A part or particle considered to be an irreducible constituent of a specified system.
        The irreducible, indestructible material unit postulated by ancient atomism.
    An extremely small part, quantity, or amount.
    Physics & Chemistry.
        A unit of matter, the smallest unit of an element, having all the characteristics of that element and consisting of a dense, central, positively charged nucleus surrounded by a system of electrons. The entire structure has an approximate diameter of 10 -8 centimeter and characteristically remains undivided in chemical reactions except for limited removal, transfer, or exchange of certain electrons.
        This unit regarded as a source of nuclear energy.