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Explanation:

Isotope notation is written as:

where A is the mass number and Z is the atomic number. A charge can be added to the right subscript if needed.

1. Find A

A is the mass number, or the sum of protons and neutrons.

There are 19 protons and 20 neutrons.

2. Find Z

Z is the atomic number of number of protons.

There are 19 protons.

3. Find a possible charge

If this is a neutral atom, the protons equal the neutrons.

There are 19 protons and 18 electrons, which is obviously not equal. This is an ion and there is a charge.

There is 1 more proton. A proton has a positive charge, so the charge must be +1.

4. Write the symbol.

A= 39, Z= 19, and the charge is +1

So, the correct answer must be choice A.

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answer:

the reaction is type of combination reaction.

explanation:

on the product side, there are 2 molecules of bonded to fe   which means one atom of fe are combined two molecules of . so, balanced chemical equation becomes :

this reaction follows the reaction type of combination reaction. a combination reaction is defined as chemical reaction in which reactants combines together to form a single product.