Metals, alloys and state symbols explained
Bonding, structure, and the properties of matter • Bonding and substance properties
Flashcards
Test your knowledge with interactive flashcards
Key concepts
What you'll likely be quizzed about
Metallic structure and bonding
Metal atoms form a regular lattice of positive ions surrounded by a sea of delocalised electrons. Strong electrostatic attraction between the positive ions and the delocalised electrons holds the lattice together. The lattice permits layers of ions to slide over each other while electrons maintain bonding, producing malleability and ductility.
Properties explained by structure
Electrical conductivity occurs because delocalised electrons move through the lattice and carry charge. Thermal conductivity occurs because electrons and vibrating ions transfer energy rapidly. Malleability and ductility occur because layers of ions can slide when a force is applied without breaking metallic bonds due to the mobile electron sea.
Definition and types of alloys
An alloy is a mixture of a metal with one or more other elements, often other metals. Substitutional alloys form when similar-sized atoms replace metal atoms in the lattice. Interstitial alloys form when much smaller atoms occupy spaces (interstices) between metal atoms. Alloy manufacturing changes mechanical properties without forming new ionic or covalent bonds.
Why alloys are harder than pure metals
Different-sized atoms in an alloy distort the regular arrangement of metal ions. Distortion creates obstacles to the movement of dislocations and sliding of layers. Reduced ease of layer movement increases yield strength and hardness. Hardness depends on the size difference and concentration of the added atoms; greater distortion produces stronger blocking of dislocation motion.
State symbols and correct usage
State symbols indicate the physical form of reactants and products in chemical equations: (s) solid, (l) liquid, (g) gas, (aq) aqueous solution. Correct placement of state symbols follows each formula. State symbols clarify reaction conditions and allow correct interpretation of phase changes, solubility and when ionic equations are appropriate.
Key notes
Important points to keep in mind