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all the elements of a family in the periodic table have what feature in common?
they all have similar chemical properties.
they all have the same number of protons in the nucleus.
they are all located in the same horizontal row or period.
they all have the same number of electrons in the electron cloud.

They are all located in the same horizontal row or period.

Explanation:

In the periodic table the elements are arranged according to their increasing atomic number.The elements those contain low atomic number are placed in the first row such as hydrogen and helium. similarly the radioactive elements those have high atomic number are placed in 7th or 8th row.

     All the elements of a family in the peroidic table have common features are located in same horizontal row or period.For example fluorine,chlorine,bromine and iodine are placed in VII B class of periodic table as all of them are electronegative in nature.

2fe + 3h2so4 -> fe2(so4)3 + 3h2

it is necessary to balance equations in order to get the proper amount of reactants as well as products in order not to make a miscalculation.

you cannot change the subscripts as that would change the substance itself. for instance, diatomic elements such as h2 only have the subscript two when a gas. another example would be so4, if you were to change the subscript, the element would no longer be sulfate.

we change the coefficients instead as that only changes the number of molecules rather than the substance itself.

hope this !

just did the assignment and the answer was #1 +2 n