Dont react with other elements because their

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don’t react with other elements because their outermost energy level is filled - located in the far right column TYPES OF COMPOUNDS Molecular   Compounds  are composed of 2 or more nonmetals covalently bonded    (electrons are shared in covalent bonds)      (nonmetals are the elements in the triangle and Hydrogen) - made up of molecules        molecule  – neutral group of atoms that act as a unit - liquid or gas at room temperature; low boiling point; low melting point Ionic Compounds  are composed of oppositely charged ions held together by ionic bonds     (electrons are transferred in ionic bonds)        ion  – atom or group of atoms that have non-equal #’s of p +  & e -        polyatomic ion  – tightly bound group of atoms that act as a unit and carry       a charge             cation  = positive ion anion  = negative ion - made up of formula units      ( formula unit  – lowest whole # ratio of ions in an ionic cmpd.) - crystalline solids at room temperature Ionic Charges of the Group A Elements 1A 2A 3A 4A 5A 6A 7A H + Li + Be +2 B +3 N -3 O -2 F -1 Na +1 Mg +2 Al +3 P -3 S -2 Cl -1 K +1 Ca +2 Se -2 Br -1 Rb +1 Sr +2 I -1
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Cs +1 Ba +2 Metals lose electrons  to form  positive ions  (ca t ions). For metals in groups 1A,2A, & 3A : numerical charge = group # Nonmetals gain electrons  to form  negative ions  (anions) . For nonmetals in groups 5A, 6A, & 7A: numerical charge = 8 – group # FORMULA WRITING OF CHEMICAL COMPOUNDS chemical formula  – shows the kinds and numbers of atoms in the smallest unit of     a compound - lowest whole number ratio Ex:  H 2 O is composed of 2 hydrogen atoms and one oxygen atom - subscript denotes the number of atoms of the element it follows - the most positive element is written first (the closer to fluorine, the more negative the element is) - the net charge of the molecule is zero because it is neutral binary compound  – composed of 2 elements ternary compound
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