Law of Octaves :
Law of Octaves John Newlands (Br) – 1863
Arranged elements in order of increasing atomic mass
Noted a repetition of properties every 8th element
Mendeleev’s Periodic Table :
Mendeleev’s Periodic Table Proposed element properties are a function of their atomic masses
Put elements in periods (rows); unlike Newlands, Mendeleev’s rows were not all the same
1st 2 periods = 7 elements
2nd 2 periods = 17 elements
An important life lesson:Perseverence Pays Off :
An important life lesson:Perseverence Pays Off Both Mendeleev and Lothar Meyer (Gr) came up with similar tables of the elements
Both had “blank spots” on their table
Mendeleev made predictions about the “missing elements”
Predictions were very accurate
As a result, we hear more about Mendeleev than we do about Meyer
Mendeleev’s Predictions(Table 6.3, p. 139) :
Mendeleev’s Predictions(Table 6.3, p. 139) Ekasilicon
Atomic mass: 72
High Melting Point
Density: 5.5 g/cm3
Dark gray metal
Will form a compound with oxygen, 1:2 ratio; Density (of EsO2) = 4.7 g/cm3 Germanium
Atomic mass: 72.61
Melting Point: 945°C
Density: 5.323 g/cm3
Gray metal
Forms GeO2, with a Density = 4.70 g/cm3
Periodic Law – Properties of elements are a periodic function of their atomic masses :
Periodic Law – Properties of elements are a periodic function of their atomic masses Problem: Tellurium and Iodine were switched; Cobalt and Nickel, and Argon and Potassium were also switched
Inaccurate masses?
Henry Moseley – each element has a specific number of protons in the nucleus Modern Periodic Law
Properties of elements are a periodic function of their atomic numbers
Metals, Nonmetals, & Metalloids :
Metals, Nonmetals, & Metalloids Metals (Left side/Center)
Properties – Shiny, malleable, ductile, conductor
Nonmetals (Right side)
Properties – Dull, brittle, poor conductor
Metalloids (Stair-step line b/w metals & nonmetals; Exception: Aluminum)
Properties – some metallic, some nonmetallic