Question

Identify the missing information for each atom or ion. Note that the atoms and ions are not necessarily neutral.

A Se ion has a mass number of 78 and a charge of −2 . Determine the number of neutrons, protons, and electrons in this ion.
number of neutrons:
number of protons:
number of electrons:

Answer 1

Number of neutrons: 44

Number of protons: 34

Number of electrons: 36

Step-by-step explanation:

The atomic number of Se (Selenium) is 34

Mass number is 78

Number of neutrons = mass number - atomic number = 78 - 34 = 44

Number of protons is the same as the atomic number

Number of protons = 34

Selenium ion has a charge of -2. This means it accepts two more electrons

Number of electrons = atomic number + 2 = 34 + 2 = 36