DSE Chem revision
Topic 2. Microscopic World I
A. Atomic structure
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elements, atoms and symbols
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classification of elements into metals, non-metals and metalloids
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Subatomic particles in the nucleus:
protons: positive charge
neutrons: no charge
electrons : negative charge -
simple model of atom
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Atomic number (Z): no. of protons in the nucleus
Mass number (A):no. of protons and neutrons in the nucleus -
Isotopes: different atoms of the same element, having the same no. of protons but different no. of neutrons
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isotopic masses and relative atomic masses based on 12C=12.00
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electronic arrangement of atoms (up to Z=20)
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stability of noble gases related to their electronic arrangements - octet rule
B. The Periodic Table
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the position of the elements in the Periodic Table related to their electronic arrangements
Period no. = no. of occupied electron shell(s)
Group no. = no. of outermost shell electron(s) -
Group I: Alkali metals
Li, Na, K, Rb, Cs, Fr -
Group II: Alkaline earth metals
Be, Mg, Ca, Sr, Ba, Ra -
Group VII: Halogens
F, Cl, Br, I, At -
Group 0: Noble gases
He, Ne, Ar, Kr, Xe
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similarities in chemical properties among elements in Groups I, II, VII and 0
C. Ionic bond
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the electrostatic attraction between cation nd anion
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formed by transfer of electrons
metals lose electrons to form cations
non-metal gain electrons to form anions -
electron diagrams of simple ionic compounds
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names and formulae of ionic compounds
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ionic structure as illustrated by NaCl
D. Covalent bond
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electrostatic attraction between nuclei and shared electrons
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formed by sharing of electrons in the formation of covalent bond
single bond: each atom shares 1 e-
double bond: each atom shares 2e-
triple bonds: each atom shares 3e- -
electron diagrams of simple covalent molecules
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names and formulae of covalent compounds
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formula masses and relative molecular masses
E. Metallic bonding
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Structures and properties of metals
F. Structures and properties of substances
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simple molecular structures
giant ionic structures
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giant covalent structures
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giant metallic structures
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Comparison of structures and properties of important types of substances
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