valency

• Atoms can either be: Positively charged, negatively charged or neutrally charged
• In a compound, the charge of both elements would have to cancel out each other that results in a neutral charge
• For example, in NaCl, Na (sodium) has a charge of +1 and is a group 1 metal. It will donate one electron to chlorine which is a group 7 non metal as it is electronegative, and will gain one electron and hence a -1 charge. Hence, when they chemically bond, the charges would cancel each other out and the compound will become neutral
• Transition metals, which are located in between groups 3 to 12 share different amounts of electrons which would cause them to form more than one ion, for example Iron(II) and Iron(III) vary due to the fact that in Iron(II) compounds only two electrons are shared whereas Iron(III) 3 electrons are shared

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There are 3 types of bonding:

→ ionic bonding

→ covalent bonding

→ metallic bonding

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ionic bonding

• Ionic bonds are chemical bonds that are usually formed between a metal and a nonmetal and is formed by the electrostatic attraction between oppositely charged metal and non metal ions.
• For an atom to gain stability, it will need its outmost octet to be complete (all 8 electrons present)
• Atoms gain stability through giving or taking electrons to or from other atoms, hence ions are created

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Ions are charged atoms. There are 2 types of ions, a cation and an anion. A cation is a positively charged atom that is a metal and has donated its electron, and an anion is a negatively charged ion which has received an electron

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• Due to their low electronegativity, metal atoms donate electrons to non-metal ions to form stable atoms with oppositely charged ions with full outer shells. Due to an electrostatic attraction between the 2 opposite charges, thus results an ionic bonds which forms a giant structure also known as an ionic compound

Lewis Dot and Cross Diagram:

Na is very unstable since it only has 1 electron in its outer shell Cl is highly reactive since it has 7 electrons in its outer shell and only needs 1 more

• Chemical formulae are written within nuclei

• Only valence electrons of elements are drawn

• Electrons of one element are shown as crosses, whereas electrons of another element are

  shown as dots so as to demonstrate electron transfer

• Brackets are used to display bonding between elements

• Charges are written outside of brackets

Properties:

• Ionic substances form giant lattices containing oppositely charged ions and can continue to build
• The arrangement does not have like charges together because they will repel each other
• High melting and boiling points
  • Electrostatic charges in ionic compounds are strong and need more energy in order to break them
• Form crystals in a cubic shape when solid
  • Due to structure of lattice
• Brittle, shatter when hit
  • When the lattice is hit, a layer of ions is shifted, causing similarly charged ions to line up and repel each other
• Do not conduct electricity when solid
  • Ions are fixed in position and cannot move around
• Can conduct electricity when liquid
  • When in liquid state, ions are free to move around and conduct electricity

covalent bonding