atomic structure & periodic table Flashcards
relative atomic mass (A subscript r) definition
-the weighted mean of the mass numbers of the isotopes of an element, taking into account the abundances of the various isotopes of the element
general formula for calculating Ar
(% x mass no. of isotope A) + (% x mass no. of isotope B)…
Mr(subscript r) =
the gfm
first 20 elements of the periodic table
- H, He
- Li, Be, B, C, N, O, F, Ne
- Na, Mg, Al, Si, P, S, Cl, Ar
- K, Ca
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group vs period number
- group number of the element = no. of electrons in the outer shell
- period number of the element = no. of electron shells
group names
group 1: alkali metals
group 2: alkali earth metals
group 7: halogens
group 8/0: noble gases
isotopes
- same atomic number, different mass numbers
- isotopes of the same element have the same chemical properties