Key Terms

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Last edited 25 days ago by Learn LoopHQ.

Chapter: 03. Elements And Compounds

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Pure substance: A substance that contains same kind of particles (atoms or molecules).

Impure substance or mixture: A substance that contains two or more pure substances (elements or compounds or both) physically mixed in any proportion.

Homogeneous substances: Substances that have a uniform composition.

Heterogeneous substances: Substances that do not have a uniform composition.

Element: A pure substance made up of only one kind of atoms that cannot be split into two or more simpler substances by any physical or chemical method.

Atom: The smallest unit of an element.

Metals: Elements generally characterized by being solid (except mercury), hard, lustrous, malleable, ductile, sonorous, and good conductors of heat and electricity.

Non-metals: Elements generally characterized by being soft (except diamond), non-lustrous (except iodine), brittle, non-malleable, non-ductile, non-sonorous, and bad conductors of heat and electricity (except graphite).

Metalloids: Elements that show some properties of metals and some properties of non-metals.

Noble or Inert Gases: Gaseous elements that do not react chemically with other elements.

Rare Gases: Another name for noble or inert gases, given because they are found in traces.

Symbol: The abbreviation used to denote an element.

Compound: A pure substance made up of two or more elements chemically combined in a fixed proportion by mass.

Molecule (of a compound): The smallest unit of a compound that exhibits all the properties of that compound and has an independent existence.

Molecule (of an element): Formed when two or more atoms of the same element combine.

Atomicity: The number of atoms present in the molecule of an element.

Monoatomic molecule: A molecule containing one atom.

Diatomic molecule: A molecule containing two atoms.

Triatomic molecule: A molecule containing three atoms.

Tetraatomic molecule: A molecule containing four atoms.

Polyatomic molecule: A molecule containing more than four atoms.

Formula: The short way of representation of the molecule of an element or a compound.

Periodic Table: A systematic arrangement of elements in a tabular form.

Minerals: The combined forms in which most metals are found on the earth.

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