Answer1)https://media.cheggcdn.com/media%2F873%2F8734f30f-4644-435d-9b47-186eeb24b753%2FphpkLyVwJ.png

Answer2)https://d2vlcm61l7u1fs.cloudfront.net/media%2Fc98%2Fc980a85e-aa6c-4ffd-ba8b-ee7562864a10%2FphpJHYQsy.png

Answer3)Atomic number of Ba is 56 (This we get from periodic table)
mass number is 135 (This is given in question)

number of proton is same as atomic number
So,
number of proton = 56

number of neutron = mass number - atomic number
= 135 - 56
= 79

charge is +2 (this is given in question)
use:
charge = number of proton - number of electron
+2 = 56 - number of electron
number of electron = 54

Answer4)https://d2vlcm61l7u1fs.cloudfront.net/media%2F890%2F8903c31e-4db6-4cfb-9f1d-16a8e128ef84%2FphpP5OhQu.png

Answer5)https://d2vlcm61l7u1fs.cloudfront.net/media%2F900%2F9001bd90-a0bd-417e-b063-6f8375ae56c9%2Fphpy8cwHA.png

Answer6)https://d2vlcm61l7u1fs.cloudfront.net/media%2F3d9%2F3d981ad0-1230-4fe2-a414-b5af22acd477%2FphpVwaV9k.png

Answer7)https://d2vlcm61l7u1fs.cloudfront.net/media%2Fe43%2Fe434fa6d-b689-4ee5-87bf-169f8a3460fe%2FphpEzJavF.png

Answer8)69.66    = 68.925580*x + 70.9247005 *(1-x)

x     = 0.6326

The percent abundance of 1st isotope   = 63.26%

The percent abundance of 2nd isotope   = 1-x   = 1-0.6326   = 0.3674   = 36.74%

Answer9)NOTE—link had a poor rating
1)

Atomic number of Se = 34

So, number of proton = 34

use:

charge = number of proton - number of electron

-2 = 34 - number of electron

number of electron = 36

number of neutron = mass number - atomic number

= 78 - 34

= 44

Answer:

44

34

36

2)

number of proton = mass number - number of neutron

= 65 - 36

= 29

29 is atomic number for Cu

use:

charge = number of proton - number of electron

+1 = 29 - number of electron

number of electron = 28

Answer:

Cu

29

28

3)

Atomic number is 36 for Kr

use:

charge = number of proton - number of electron

= 36 - 36

= 0

use:

mass number = number of proton + number of neutron

= 36 + 42

= 78

Answer:

Kr

78

0

Answer10)https://d2vlcm61l7u1fs.cloudfront.net/media%2F513%2F5138ce57-73ca-4c4b-ab54-252763310e9a%2FphpkUpQmx.png