Question

how many electrons are in this polyatomic ion: Cr2O7 2- (dichromate ion)?

Answer 1

Explanation:

we know,

atomic number = proton = electron

Step 1: Identify the atomic number of each elements of molecules

Step 2: multiply the atomic number by the total atoms of each element

Step 3: Add all the value of each of the element

Step 4: Final step

1. If the charge is positive then  subtract the number from the add value we got in step 3 to get the number of electrons.
2. If the charge is negative then add the number to  the final add value we got in step 3 to get the number of electrons.

Calculation :

Step 1: Identification of atomic number

Given, Cr₂O₇^-2

Atomic number of Cr = 24

Atomic number of O = 8

Step 2: multiply the atomic number by the total atoms of each element

In Cr₂O₇^-2 = there are 2 cr atoms and 7 O atoms

so, Cr = 2 atoms of Cr × 24 electrons / atom of Cr = 48 electrons

O = 7 atoms of O × 8 electrons / atoms of O = 56 electrons

Step 3: Addition of electrons

we got.

O = 56 electrons

Cr = 48 electrons

so total value of electrons = 56 electrons + 48 electrons =  104 electrons

Step 4: Calculation of total electron

Here. Cr₂O₇^-2 which means charge on the ion is negative

[ If the charge is negative then add the number to  the final add value we got in step 3 to get the number of electrons.]

we got Total electrons of Cr₂O₇^-2   = 104 +2 = 106 electrons