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1. Atoms are the smallest unit of an element that still retain the chemical and physical properties of the element.

2. Mostly empty space with its mass concentrated in the central nucleus.

3. The nucleus contains nucleons (protons & neutrons).

4. Protons are positively charged, neutrons have zero charge.

5. Atoms are electrically neutral (number of protons = number of electrons).

6. Mass number (A) = number of protons + neutrons.

7. Atomic number (Z) = number of protons.


1. Bushberg, J. T. (2012). The essential physics of medical imaging. Philadelphia: Wolters Kluwer Health/Lippincott Williams & Wilkins. Find it at Amazon
2. Heggie, J. C., Liddell, N. A., & Maher, K. P. (1997). Applied imaging technology. Melbourne: St. Vincents Hospital.

Ⓒ A. Manickam 2018

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