Question

Define the following terms:

Answer 1

1.Atom is the smallest particle of a substance that can exist by itselfor be combined with other atomsto form a 
molecule.
2.Isotope is any one of variousforms in which the atoms of a chemical element can occur.
3.Atomic number is a an experimentally determinednumber characteristic of a chemical element that represents the number of protons in the nucleus which in a neutral atom equals the number of electrons outside the nucleus and that determines the place of the element in the periodic table — see element table.
4.The atomic number or proton number (symbol Z) of a chemical element is the number of protons found in the nucleus of an atom. 
5.In nuclear engineering, a neutronmoderator is a medium that reduces the speed of fast neutrons, thereby turning them into thermal neutrons capable of sustaining a nuclear chain reaction involving uranium-235 or a similar fissile nuclide.

(Hope it helps)

Answer 2

Hello sister ,

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# atom => matter is made up of tiny particals is called as atom

# isotope => which elements have same atomic number but different mases

example => species of hydrogen

# atomic number => atomic number is the number of proton or number of electron

# atomic mass => the sum of number of proton and number of neutrons is called atomic mass

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