What is the mass defect of lithium? assume the following:
atomic number of lithium = 3
atomic mass of lithium = 7.0144 atomic mass units.
mass of 1 proton = 1.0073 atomic mass units.
mass of 1 neutron = 1.0087 atomic mass units.

Δm = 3.0684

Explanation:

Data Given:

Atomic number of lithium = 3

Atomic mass of lithium = 7.0144 amu

Mass of 1 proton = 1.0073 amu

Mass of 1 neutron = 1.0087 amu

Solution:

Mass Defect:

Mass defect is the difference of mass number of an atom and its atomic number.

Formula used

Δm = [Z (mass of proton + mass of nutron)  + ( A − Z ) mass of nutron] − m of atom

where:

Δm = mass defect (amu)

Z = atomic number

A = mass number

Put values in formula

Δm = [3 ( 1.0073 amu + 1.0087 amu)  + ( 7 − 3 ) 1.0087 ] − 7.0144

Δm = [3 (2.016)  + (4) 1.0087 ] − 7.0144

Δm = [(6.048)  + (4.0348) ] − 7.0144

Δm = 10.0828 − 7.0144

Δm = 3.0684