The mass number is the summation of number of proton and neutron present in a nucleus of an atom. For the neutral atom the number of positive charge (number of proton) must be equal to the number of electrons. The number of electrons present in an atom is the atomic number of the atom. The standard way to express the mass number (a) and atomic number (m) of a atom (say X) is 
. Now for silicon number of electron or atomic number is 14. And the mass number (a) given 29. Thus the expression nucleus of silicon will be 
Answer:
2. Full
Explanation:
A lunar eclipse occurs at a full moon when Earth is directly between the moon and the sun. During a lunar eclipse, Earth blocks sunlight from reaching the moon.
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<u>Given:</u>
Distance of solvent front = 68 mm
Distance of unknown = 48 mm
<u>To determine:</u>
The rf value
<u>Explanation:</u>
The retention factor or the rf value is given by the ratio of distance traveled by the unknown to the distance traveled by the solvent front
RF = distance by unknown/distance by solvent
RF = 48/68 = 0.706
Ans: the RF value is 0.706
