Periodic Classification of Elements and Metallurgy
Periodic Classification of Elements and Metallurgy tests Mendeleev's and the modern periodic table, periodic trends, and the extraction of metals from ores. Expect electronic configuration, position in the table and metallurgical steps.
Core rules
- Mendeleev arranged elements by atomic mass and left gaps for undiscovered elements. The modern table arranges elements by atomic number.
- Groups are vertical columns with similar valence electrons; periods are horizontal rows with the same number of shells. Group 1 is alkali metals, group 17 halogens, group 18 noble gases.
- Across a period, atomic radius generally decreases and non-metallic character increases. Down a group, atomic radius increases and metallic character increases.
- Metallurgy: concentration of ore, roasting or calcination, reduction to metal, then refining. Roasting heats a sulphide ore in air; calcination heats a carbonate ore in limited air.
- Alloys are mixtures of metals with other elements, made to improve properties such as strength or corrosion resistance.
Worked example
An element has atomic number 17. Its electronic configuration is 2, 8, 7. Three shells mean period 3; seven valence electrons mean group 17. It needs one electron to complete its octet, so its valency is 1 and it is a non-metal, a halogen. The reasoning uses atomic number first, then shell count and valence electrons.
Traps
Do not place elements by atomic mass in the modern table. Group number is not the same as period number. Roasting and calcination are not interchangeable. Reduction does not always use carbon. Alloys are mixtures, not compounds with fixed formulas.