1. Who was the first person to create a periodic table? When? 2. What is the modern periodic table?

3. Compare and contrast the periods and groups of the modern periodic table.

4. In the modern periodic table (found in the back of your agenda), find the element named lead (Pb). How many protons do atoms of lead have? To which class of elements does lead belong?

5. Most of the elements on the periodic table belong to what class of elements.

6. Which groups of the modern periodic table contain elements that are classified as metalloids?

Mendeleev discovered the periodic table (or Periodic System, as he called it) while attempting to organise the elements in February of 1869.

Explanation:

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 !