General Chemistry Online: Companion Notes: Compounds: Classifying compounds: Ionic vs. molecular

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Companion Notes

Compounds

Classifying compounds

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Table of Common Molecular Compounds. These compounds are very common and have names that don't follow the usual naming conventions for molecular compounds. They should be memorized.

Name Formula Name Formula

ammonia NH₃ methane CH₄

carbon dioxide CO₂ nitrous oxide N₂O

carbon monoxide CO nitric oxide NO

hydrazine N₂H₄ sulfur dioxide SO₂

hydrogen peroxide H₂O₂ water H₂O

hydrogen sulfide H₂S

Ionic compounds

definition: Ionic compounds are compounds built from positive ions (cations) and negative ions (anions).
origin: electron transfer creates anions & cations, which attract because of their opposite charges

Metals are good electron donors, and nonmetals are good electron acceptors.

electron acceptor (Cl)
meets
electron donor (Na)

electron jumps from Na to Cl
longrightarrow

ions attract
to form
neutral pair

structure: smallest building blocks are ions- not molecules!
- large numbers of ions can attract to form clusters and eventually crystals
  
  an ion pair
  an ion cluster
  an ion crystal
- ions can separate when compound is dissolved, melted, or vaporized

Comparing ionic and covalent compounds

Quiz
classifying compounds as ionic or covalent

Table: Comparing ionic and molecular compounds.

	Molecular compounds	Ionic compounds
smallest particles	molecules	cations and anions
origin of bonding	electron sharing	electron transfer
forces between particles	strong bonds between atoms weak attractions between molecules	strong attractions between anions and cations strong repulsions between ions of like charge
elements present	close on the periodic table	widely separated on the periodic table
metallic elements present	rarely	usually
electrical conductivity	poor	good, when melted or dissolved
state at room temperature	solid, liquid, or gas	solid
melting and boiling points	lower	higher
other names	covalent compounds	salts

General Chemistry Online! Ionic vs. molecular