18. Challenge: An adult elephant (-37 years old, -3600 kg, and a hind-gut fermenter) has a day iron requirement of 50 mg of Fel kg of elephant. Using the accepted value of mg of Felg of spinach given
below as a conversion factor, determine the amount of spinach in kilograms that an elephant mas
consume daily if spinach is its only source of iron. (You'll have several steps to your calculations)

petroleum? coal maybe?

explanation:

let the different atoms be x and y. each with four protons and same mass will be represented as follows.

mass number is number of protons + number of neutrons.

            and  

since, it is given that one has a negative charge while the other is neutral. therefore, there will be increase in number of protons and the atom will be represented as follows.

according to periodic table, mass number of beryllium is 9 and it has atomic number 4 so, the atoms will be and .  

the protons and neutrons will be located inside the nucleus whereas the electrons will be revolving around the nucleus.  

i do not get it   at all