Gave SAT 2 today and encountered this question in chemistry:
St 1-Lithium, sodium and potassium have similar chemical properties
St 2-They have same number of valence electrons.
Most of my friends are saying that the answer is both the statements correct and statement 2 is the correct explanation of statement one.
However I think that statement 1 is false because Lithium exhibits diagonal relationship with magnesium and has anomalous behavior which results in different chemical properties like
Lithium forms monoxide while sodium and potassium form peroxides
Lithium forms nitride unlike other alkali metals
It’s carbonates and nitrates decompose on heating unlike other alkali metals.
LiCl is soluble in water unlike other alkali metal chlorides.
Please tell me who is correct.
Your friends are correct.
Lithium, sodium and potassium form oxides in the form X2O
The others form nitrides too.
The carbonates and nitrates of all of them decompose on heating.
NaCl isn’t soluble in water??
You are over thinking this. You don’t need to know what compounds they form or how the compounds act.
ST1 says their properties are similar. It doesn’t say identical. By definition, elements from the same Group have similar properties. And why is that? Because they have the same number of valence electrons. (ST2)
The successful student will be able to identify the elements by symbol from the names given in the question. He will see that they are in the same Group. He needs to know that Group 1 elements have similar properties because they all have 1 valence electron.
It is true that Lithium is more similar to Magnesium than other alkali metals but the rule of thumb says that whatever it does, it is an alkali metal only. Looks like I have to give another time SAT 2.