Elements, Compounds and Mixtures

Elements

• Over 100 different elements have been discovered.

  • These elements are organised in the Periodic Table of Elements.
  • Some symbols are derived from their Latin names, such as Na for sodium (Natrium).
  • The first letter is always capitalised; if there is a second letter, it is lowercase (e.g., Helium = He).

• Each element has a symbol, usually one or two letters, typically derived from its name.

Robert Boyle

Robert Boyle, an Irish scientist from Lismore, Co. Waterford, defined the concept of an element.

Compounds

• Compounds consist of two or more different elements chemically combined.eg, MgO, H2O, FeS, and NaCl.
• When elements combine, their separate properties are lost and they gain new properties.
• Generally, elements are combined and heated to chemically bond. HYDROGEN gas can be combined with OXYGEN to make WATER (H₂O)

Formula	Element	Description
H₂O	Hydrogen	An explosive gas
	Oxygen	A highly flammable gas
	Water	A liquid
CO₂	Carbon	A black sooty solid
	Oxygen	A highly flammable gas
	Carbon dioxide	A gas that puts out fires

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Mixtures

• Examples of mixtures include air, seawater, crude oil, tea
• Iron and sulfur mixed together form a mixture.
• Mixtures are easy to separate.

Differences Between Mixtures and Compounds

Mixture	Compound
Properties are similar to the elements within	Properties are different from the elements
Contains two or more substances	One substance
Mostly easy to separate the substances	Very difficult to separate the elements

Iron and Sulfur Experiment

This experiment demonstrates the difference between mixtures and compounds.