Re: what is less reactive platinum or gold, is hydrogen a metal as it is often

Hi Tim: You asked what is less reactive platinum or gold?  Is hydrogen a 
metal as it is in group 1 of the periodic table with lithium Li, sodium, 
Na, cesium Cs etc.? 

The distinction between metals and non metals is not as distinct as we 
often would like it to be. Those elements that easily loose electrons to 
from positive ions are  called metals. Elements that are metals
have the following physical properties; lustrous appearance, malleable, 
high density, good conductors of heat and electricity. They form basic 
oxides with oxygen. Metals are electropositive. Metals above
hydrogen in the electromotive series will displace hydrogen from acids. 
Hydrogen is, by the above definition, not a metal. It is in group one of 
the periodic table because it has one electron in its outermost shell.

--- Dan Berger adds: sometims (very seldom) H is placed in Group 17 of the 
    periodic table because it can form a basic anion by gaining one electron.

Metals can be grouped in order of their electrode potential.  This is 
called the electrochemical series. Metals which are higher in the 
electrochemical series displace metals which are lower. Hydrogen has an
electrode potential of +0.00.

As to which is more reactive platinum or gold the answer is platinum with 
an electrode potential of +1.18 while gold has an electrode potential of 
+1.70. 

             	Element	    Potential (Volts)	
             	=======	    =========
             	Lithium	    -3.04	
             	Potassium   -2.92	
             	Calcium	    -2.87	
	        Sodium	    -2.71	
	        Magnesium   -2.37	
	        Aluminum    -1.67	
             	Manganese   -1.85
               	Zinc 	    -0.76	
	        Chromium    -0.74	
	        Iron        -0.44	
	        Nickel      -0.26	
	        Tin         -0.14	
	        Lead        -0.13	
	        Hydrogen    +0.00	
	        Copper      +0.34	
	        Silver      +0.80	
                Mercury     +0.80
                Platinum    +1.18
                Gold        +1.70	

A negative value for electrode potential means that the element loses 
electrons more readily than hydrogen (i.e., it is better reducing agent). 
A positive value for electrode potential means that the element is a poorer 
reducing agent than hydrogen. 

A strong oxidizing agent has a large positive potential and a strong 
reducing agent a large negative
potential.