Identify the missing elements from the following Dobereiner's triads.

Q. Give alongside is a part of the periodic table :
As we move horizontally from left to right:

Li	Be		B	C	N	O	F
Na	Mg		Al	Si	P	S	Cl

(i) What happens to the metallic character of the elements?
(ii) What happens to the atomic size?

Q. State whether the following elements belong to a Group (G), Period (P) or Neither Group nor Period (N).

Elements	G/P/N
$Li,C,O$
$Mg,Ca,Ba$
$Br,Cl,F$
$C,S,Br$
$Al,Si,Cl$
$Li,Na,K$
$C,N,O$
$K,Ca,Br$

Q. From the given table, identify the set of metals that cannot be extracted from their ores using carbon reduction method.

Q.

Given below are a few elements arranged in the order of increasing atomic masses.
Identify the pair of elements with similar properties according to Newlands’ Law of Octaves.

Q.

Complete the following table relating to the atomic structure of some elements.

$\begin{array}{cccccc}\text{Element}& \text{Atomic}& \text{Mass}& \text{Number of}& \text{Number of}& \text{Number of}\\ \text{Symbol}& \text{Number}& \text{Number}& \text{Neutrons}& \text{Electrons}& \text{Protons}\\ Li& 3& 6& & & \\ Cl& 17& & 20& & \\ Na& & & 12& & 11\\ Al& & 27& & & 13\\ S& & 32& 16& & \end{array}$