What are Atoms?

What are Atoms?

1. Definition: the basic unit of a chemical element.

2. Neutrons: a subatomic particle of about the same mass as a proton but without an electric charge, present in all atomic nuclei except those of ordinary hydrogen.

   • Isotopes: each of two or more forms of the same element that contain equal numbers of protons but different numbers of neutrons in their nuclei, and hence differ in relative atomic mass but not in chemical properties; in particular, a radioactive form of an element.
   • Radioactive: emitting or relating to the emission of ionizing radiation or particles.

3. Electrons: are subatomic particles that hold an elementary charge of magnitude -1.

4. Protons: a positively charged elementary particle that is a fundamental constituent of all atomic nuclei.

5. Elements: each of more than one hundred substances that cannot be chemically interconverted or broken down into simpler substances and are primary constituents of matter. Each element is distinguished by its atomic number, i.e. the number of protons in the nuclei of its atoms.

6. Mass number: the total number of protons and neutrons in a nucleus.

7. Atomic nucleus: The atomic nucleus is the small, dense region consisting of protons and neutrons at the center of an atom

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