<span>There is a direct correlation between the period number and the energy level for valence electrons. For example, the H and He elements, in period 1, have their outer electrons in the energy level "1". This continues down the rows: all the elements in period 2 have their principal energy level as n = 2, period 3 has n = 3, and so on.</span>
Answer: Option (a) is the correct answer.
Explanation:
A decomposition reaction is defined as a reaction where a compound dissociates into two or more atoms.
For example, 
Whereas a chemical reaction in which two reactants combine together to result in the formation of a compound is known as a synthesis reaction.
For example,
is a synthesis reaction.
Thus, we can conclude that the statement chemical reaction A, because the reactant is a compound identifies the decomposition reaction and describes a substance is involved.
Answer:
volume of 
Explanation:
Firstly balance the given chemical equation,

From the given balance equation it is clearly that,
2 mole of Li gives 1 mole of H2 gas
⇔
⇔
⇔
hence
3 mole of Li will give 1.5 mole H2 gas
therefore volume of gas produced from 3 mole Li at 
volume of H2=33.6 litre
Explanation:
Sugar - Pure substance
Magnesium Ribbon - Pure Substance
Vegetable soup Heterogeneous mixture
Bath oil - Homogeneous mixture
Tin of assorted biscuits - Heterogeneous mixture
Peanuts and raisins - Heterogeneous mixture
Copper wire - Pure Substance
Bicarbonate of soda (Baking soda) - Pure Substance
Answer: secondary structure
Explanation: