ATOMIC STRUCTURE

 Al D. Deacon 

Founder: Gold'N Geniuz 

Physicist and Educator 

1. Describe with Illustrations, the Structure of Atoms of Atomic Number 1 to 20

• Atomic Structure: Atoms consist of a nucleus (protons and neutrons) surrounded by electrons in energy levels (shells).
• Electron Arrangement for Atomic Numbers 1 to 20:
  • 1st Shell: Holds up to 2 electrons.
  • 2nd Shell: Holds up to 8 electrons.
  • 3rd Shell: Holds up to 8 electrons (for first 20 elements).
• Example:
  • Hydrogen (Z=1): 1 electron in 1st shell.
  • Carbon (Z=6): 2 electrons in 1st shell, 4 in 2nd shell.
  • Calcium (Z=20): 2 in 1st, 8 in 2nd, 8 in 3rd, 2 in 4th shell.

(Illustrations should include Bohr diagrams for elements from Hydrogen to Calcium.)

2. State Properties of Electrons, Protons, and Neutrons

Particle	Symbol	Charge	Mass (Relative)	Location
Proton	p⁺	+1	1	Nucleus
Neutron	n⁰	0	1	Nucleus
Electron	e⁻	-1	~0 (1/1836)	Electron shells

3. Define Atomic Number and Mass Number

• Atomic Number (Z): The number of protons in an atom (determines the element).
  • Example: Carbon (Z = 6) has 6 protons.
• Mass Number (A): The sum of protons and neutrons in an atom.
  • Example: Oxygen-16 has 8 protons + 8 neutrons = Mass Number 16.

4. Define Relative Atomic Mass (Ar)

• The Relative Atomic Mass (Ar) of an element is the weighted average of the atomic masses of its isotopes compared to 1/12th of the mass of a carbon-12 atom.
• Formula: $$Ar = \frac{\sum (\text{isotopic mass} \times \text{abundance})}{100}$$
• Example: Chlorine has two isotopes, Cl-35 (75%) and Cl-37 (25%): $$Ar = \left(35 \times 0.75\right) + \left(37 \times 0.25\right) = 35.5$$

5. Interpret Notations of the Form

• Standard Notation: $$^{A}_{Z}X$$
  • A = Mass Number (Protons + Neutrons)
  • Z = Atomic Number (Protons)
  • X = Element Symbol
• Example:
  • Carbon-12: $\ ^{12}_{6}C$ (6 protons, 6 neutrons)
  • Oxygen-16: $\ ^{16}_{8}O$ (8 protons, 8 neutrons)

6. Define Isotopy

• Isotopes are atoms of the same element with the same number of protons but different numbers of neutrons.
• Example:
  • Hydrogen Isotopes: Protium (¹H), Deuterium (²H), Tritium (³H)
  • Carbon Isotopes: Carbon-12, Carbon-13, Carbon-14

7. List Uses of Radioactive Isotopes

Isotope	Use	Field
Carbon-14	Radiocarbon dating	Archaeology
Iodine-131	Treatment of thyroid disorders	Medicine
Cobalt-60	Cancer radiotherapy	Medicine
Uranium-235	Nuclear power generation	Energy
Technetium-99m	Medical imaging (scans)	Medicine
Americium-241	Smoke detectors	Safety