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7. 0-2 is isoelectronic with
a. Helium
b. Neon
c. Argon
d. Krypton

b. Neon

Explanation:

Problem;

         O²⁻ is isoelectronic with which noble gas;

   The ion of oxygen give is one that has gained two electrons.

 Atom of oxygen  = 2, 6

   gaining two electrons;

O²⁻  = 2, 8

Neon is also 2, 8

So O²⁻ is isoelectronic with neon

percent abundance for cu-63 can be shown as:

63 x + 65 (1-x) = 62.9296

65 - 62.9296 = 2 x

x = 1.035

thus, percent abundance for cu-63 is 1.035

percent abundance for cu-65 can be shown as:

63 x + 65 (1-x) = 64.9278

65 - 64.9278 = 2 x

x = 0.0361

thus, percent abundance for cu-63 is 0.0361

the mass spectrum of cu-63 showing the intense peak as, this isotope is found in nature more abundantly around 92.38 % in comparison to cu-65 which is found 62.58 % naturally