I would say it is a chemical change because after a while, the nails start to rust. Now they only rust after about a week though. But rust is a chemical change.
Formula mass, molar mass and Avagadro's number.
Explanation:
number of atoms in a compound can be calculated by knowing the molar mass of the compound or element, the result will be multiplied by avagadro's number (6.022*10^23)
1 mole of a substance is equal to Avagadro number of atoms.
If the number of moles is known of a compound or element its molar mass can be calculated as:
n= Weight of the compound/element given/ molecular weight of the same.
formula mass is the mass of compound ie chemical compound formed with different molecules. its mass is calculated by adding the molar masses of all the elements taking part in its assembly.
The given question is incomplete. The complete question is :
It takes 151 kJ/mol to break an iodine-iodine single bond. Calculate the maximum wavelength of light for which an iodine-iodine single bond could be broken by absorbing a single photon. Be sure your answer has the correct number of significant digits.
Answer: 793 nm
Explanation:
The relation between energy and wavelength of light is given by Planck's equation, which is:
where,
E = energy of the light = 151 kJ= 151000 J (1kJ=1000J)
N= moles = 1 = 
h = Planck's constant = 
c = speed of light = 
= wavelength of light = ?
Putting in the values:
Thus the maximum wavelength of light for which an iodine-iodine single bond could be broken by absorbing a single photon is 793 nm
(4) total number of valence electrons, because they exist in the same group.
All of the above because you didn't send us a image for reference..
