Dot & Cross Diagrams
- Dot and cross diagrams are diagrams that show the arrangement of the outer-shell electrons in an ionic or covalent compound or element
- The electrons are shown as dots and crosses
- In a dot and cross diagram:
- Only the outer electrons are shown
- The charge of the ion is spread evenly which is shown by using brackets
- The charge on each ion is written at the top right-hand corner
Ionic compounds
- Ionic bonds are formed when metal transfer electrons to a non-metal to form a positively charged and negatively charged ion
- The atoms achieve a noble gas configuration
Dot-and-cross diagrams of ionic compounds in which one of the atoms transfers their valence electrons to the other
Covalent compounds
- The atoms in covalent compounds will share their outer valence electrons to achieve a noble gas configuration
Dot-and-cross diagrams of covalent compounds in which the atoms share their valence electrons
Coordinate bonding
- Coordinate bonding or also called dative covalent bonding is formed when one atom provides both the electrons needed for a covalent bond
- In a displayed formula, the dative covalent bond is represented by an arrow
- The head of the arrow points away from the lone pair that forms the bond
Dot-and-cross diagrams of dative covalent compounds in which one of the atoms provides both the electrons in a covalent bond
Incomplete & expanded octet rule
- Some species may contain more (expanded) or less (incomplete) than eight electrons in their outer shell
Expanded octet rule
Incomplete octet rule
Odd number of electrons
- Some atoms in compounds may have an odd number of electrons in their valence shell
Incomplete octet rule
