Atomic Symbols and Valence

Atomic Symbols and Valence of Elements

Atomic Symbols

• Represented by a one- or two-letter abbreviation of the element's name
• Derived from the Latin or Greek name of the element
• Examples:
  • Hydrogen: H
  • Carbon: C
  • Oxygen: O
  • Aluminum: Al (from Aluminum)

Valence of Elements

• Valence: the combining power of an element, i.e., the number of electrons an atom can gain, lose, or share to form bonds
• Valence electrons: the outermost electrons of an atom, involved in bonding
• Types of valence:
  • Positive valence (oxidation number): the number of electrons lost by an atom
  • Negative valence (reduction number): the number of electrons gained by an atom
• Examples:
  • Hydrogen: +1 (loses 1 electron)
  • Oxygen: -2 (gains 2 electrons)
  • Aluminum: +3 (loses 3 electrons)

Periodic Table and Valence

• Elements in the same group (vertical column) have similar valence
• Elements in the same period (horizontal row) exhibit a gradual change in valence from left to right
• Metals tend to lose electrons (positive valence), while nonmetals tend to gain electrons (negative valence)

Valence and Chemical Bonding

• Valence determines the type of bonds an element can form:
  • Ionic bonds: formed between elements with large differences in valence
  • Covalent bonds: formed between elements with similar valence
• Valence and bonding determine the properties of compounds and molecules