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 77 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:

An ion has a mass number of 65, 36 neutrons, and a charge of +1 . Identify the element symbol, and determine the number of protons and electrons in this ion.

element symbol:

number of protons:

number of electrons:

An atom or ion has 41 neutrons , 36 protons, and 36 electrons. Identify the element symbol, and determine the mass number and charge for this atom or ion.

element symbol:

mass number:

charge:

Answer 1

1. Atomic number of neutral Se = 34

Given mass number is 77

So number of neutrons is (mass number - number of - Atomic number) = 43

Charge is -2

So number of protons is 34 (equal to Atomic number)

But it has two extra electrons since it has a change of -2. So number of electrons is 36.

2. Mass number= 65

Number of neutrons= 36

Atomic number= mass number - number of neutrons

=> 65 - 36 = 29

Element symbol is Copper i.e. Cu with oxidation state of +1.

Number of protons = 29 (equal to Atomic number)

Number of electrons is one less than Atomic number since it has a positive oxidation state of +1. So number of electrons= 28

3. An atom with 41 neutrons, 36 electrons and 36 protons is an isotope of Krypton

So element symbol is Kr.

Mass number= number of protons+number of neutrons = 77

Charge is 0 because number of protons and electrons is same equal to 36.