elements. what is an element? element: is a pure substance that cannot be broken down into other...
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Describing MatterElements
What is an element?Element: Is a pure substance that cannot be
broken down into other substances by chemical or physical means.
Gold( Au) Silver(AG)
Elements are the simplest of substances
It is made up of only one kind of atom. (EG) Aluminum, Zinc & Copper (Pennies)
Nitrogen, Oxygen, & Hydrogen
Can be identified by its chemical and physical properties
Particles of Elements-Atoms Atom: Is the basic particle from which all
elements are made.
Made up of protons, neutrons, and electrons
Different elements have different atoms, henceforth, different properties
Lead(Pb) Oxygen(O)
(EG) Carbon: A carbon atom has a positively charged center, or nucleus, that contains smaller particles; a cloud of negative charge surrounds it. Fig 5 p. 39
When atoms CombineChemical bonds: When atoms combine
Water
Molecules: Groups of two or more atoms held together by chemical bonds
(EG) Water: A molecule of water consists of an oxyge
atom chemically bonded to two hydrogen atoms.
Two atoms of the same element can also combine to form a molecule
(EG) Oxygen molecules consist of two oxygen atoms
O₂ O₃
Ionic Bond forms by attraction of opposite charges of valance electrons
NaCl: salt
Covalent Bond forms by sharing of valance electrons
N₂
More examples
CompoundsCompound: Is a pure substance made of two
or more elements chemically combined in a set ratio
Chemical formula: shows the elements in the compound and the ratio of atoms
When elements are chemically combined, they form compounds having properties that are different from those of the uncombined elements
Carbon Dioxide: Its chemical formula is CO2. The number 2 below the oxygen tells you the ratio of carbon to oxygen, 2 to 1 (If there is no number after the symbol, the number 1 is understood).
Different ratios mean different compounds (EG) CO
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