CHM 2045 Lecture Notes - Lecture 2: Atomic Mass, Atomic Mass (Band), Mass Number
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2. 3 the structure of the atom the atom contains: Atomic number (z) =the number ofprotons remember this! Atoms op atomic mass = (fraction of isotope ixmass ofisotope 1) + (fraction of isotope 2 x mass of isotope 2) Compounds:a substance composed of two or more elements in a fixed, definite proportion chemical formula:indicates the elements present in the compound and the relative # of atoms or ions of each. 2. 4 types ofchemical formulas: empirical formula:simplestversion ofthe formula, molecular formula:non-simplified state of the formula. Elements that exist as molecules diatomic molecules:hz, n2, 0c, f2, u2, brs, 12 remember this! all elements mustbe able to be divisible by a common factor to be considered empirical. 2. 5 classifications ofelements main group elements (or representative elements): groups:1a-viiia(or 1, 2,13-10) transition metals: groups:113-v11 b (or 3-12) 2. 6 long:losing gaining electrons cations are positively charged ions, form by losing electrons (lit mg2+) Anions are negatively charged ions, form by gaining electrons (f-, 027.
