Atomic Structure and Isotopes

Atomic Number (Z)

• Symbolized by Z
• Represents the number of protons in an atom's nucleus.
• Found on the periodic table.
• Example: For hydrogen, Z = 1 (1 proton).

Neutral Atoms

• In a neutral atom, the number of protons equals the number of electrons.
• No overall charge; positive charges of protons balance with negative charges of electrons.

Bohr Model of Hydrogen Atom

• Hydrogen Atom: 1 proton in the nucleus, 1 electron outside.
• Isotope of Hydrogen:
  • Protium (1 proton, 0 neutrons).

Isotopes

• Atoms of a single element that differ in the number of neutrons.
  • Example: Hydrogen isotopes.

Hydrogen Isotopes

1. Protium

   • 1 proton, 0 neutrons.
   • Mass number (A) = 1 (Z + N = 1 + 0).
   • Symbol: [ ^1H ]

2. Deuterium

   • 1 proton, 1 neutron.
   • Mass number (A) = 2 (Z + N = 1 + 1).
   • Symbol: [ ^2H ]

3. Tritium

   • 1 proton, 2 neutrons.
   • Mass number (A) = 3 (Z + N = 1 + 2).
   • Symbol: [ ^3H ]

Mass Number (A)

• Combined number of protons and neutrons in a nucleus.
• Formula: [ A = Z + N ]

Practice Problem: Carbon Isotope

1. Symbol: [ ^{12}_{6}C ]

   • Protons: 6
   • Electrons: 6
   • Neutrons: 6 (12 - 6).

2. Symbol: [ ^{13}_{6}C ]

   • Protons: 6
   • Electrons: 6
   • Neutrons: 7 (13 - 6).

Hyphen Notation

• Another way to represent isotopes.
• Example: Carbon-13 (C-13).

Practice Problem: Uranium Isotope

1. Symbol: [ ^{235}_{92}U ]
   • Protons: 92
   • Electrons: 92
   • Neutrons: 143 (235 - 92).

Summary

• Isotopes have the same atomic number but different mass numbers due to varying neutrons.
• Atomic structure is vital for understanding chemical properties and reactions.