Elements, Isotopes, and Ions

Elements

• An element's identity is determined by the number of protons it has.
  • Example:
  • Carbon (C) always has 6 protons.
  • Barium (Ba) always has 56 protons.
  • Zinc (Zn) always has 30 protons.
  • If the number of protons in an atom changes, it becomes a new element.

Isotopes

• Isotopes are atoms of the same element that have the same number of protons but different numbers of neutrons.
  • They are written with the name of the element, a dash, and then a number representing the total number of protons and neutrons (mass number).
  • Example:
  • Carbon-13 (C) has 6 protons and 7 neutrons.

Ions

• Typically, an atom of an element has an equal number of protons (positive charge) and electrons (negative charge).
• Ions occur when an atom gains or loses electrons:
  • If an atom has more electrons than protons, it is a negative ion (anion).
  • If an atom has more protons than electrons, it is a positive ion (cation).
• Ions play a crucial role in chemical bonding.

Summary of Changes

• If the number of protons changes, it is a completely different element.
• If the number of neutrons changes, it is an isotope of that element.
• If the number of electrons changes, it becomes an ion.

Examples of Hydrogen

• Hydrogen Isotope (Deuterium):

  • Notation: ^{2}H
  • Protons = 1
  • Neutrons = 1
  • Electrons = 1

• Hydrogen Atom:

  • Notation: H
  • Protons = 1
  • Electrons = 1

• Hydrogen Ion (H^{+}):

  • Protons = 1
  • Electrons = 0
  • Result: Loss of 1 electron.