5.1 - Basics of Compound Formation

Formation of Compounds

• A compound is formed when two or more elements combine.
• Heated sodium reacts with chlorine to form white table salt, but forms no compound with neon.
• Noble gases exist as monoatomic gases and are chemically unreactive because their atoms already have stable electron arrangements:
  • helium has a duplet electron arrangement;
  • the other noble gases have an octet electron arrangement.
• Atoms of other elements attain a stable duplet or octet electron arrangement by transferring or sharing valence electrons.
• A chemical bond forms when electron transfer or electron sharing occurs. Only valence electrons take part.

Types of Chemical Bond

Bond	Formation
Ionic bond	Electrons are transferred between atoms.
Covalent bond	Electrons are shared between atoms.

• Sodium transfers one electron to chlorine so both attain octets; two hydrogen atoms share a pair so both attain duplets.