Question

find the number of electrons in4.8grams of calcium

Answer 1

Mole is 4.8/40=3/25
Now no. electron in 1 gm. is 3*Na /25
So in 20 gm =3 *Na* 25/20 =3.75Na

Answer 2

Hi.

Here is your answer----

Given---

Mass of Calcium = 4.8 grams
Atomic mass of calcium = 40 grams.
Number of electrons in one atom of Calcium(or Atomic Number) = 20

Using the formula,

     Number of Atoms= (Mass/Atomic Mass) x Avogadro's number
                                       = (4.8/20) x 6.022 x 10^23
                                       =  1.44528 x 10^23
                                   --------------------------------------
Thus, number of atoms in 4.8 grams of Calcium is 1.44528 x 10^23.
                                                                                   -----------------------------
            Since, One atoms of Calcium contains 20 electrons
Thus, 1.44528 x 10^23 atoms-------------------------- 20 x 1.44528 x 10^23
                                                                               = 28.9056 x 10^23 Electrons
                                                                               ----------------------------------------

Thus, number of electrons in 4.8 grams of Calcium is 28.9056 x 10^23

Hope it helps.

Have a nice day.