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MCAT Physics Question — Electron Capture Reaction

  • by John
  • Sep 19, 2014
  • MCAT Question of the Day

What happens to the mass number and atomic number during an electron capture reaction?

 

a) mass number decreases and atomic number decreases

b) mass number decreases and atomic number stays the same

c) mass number stays the same and atomic number decreases

d) mass number increases and atomic number increases

 

Explanation

In an electron capture reaction, an electron merges with a proton to create a neutron. Since one proton is lost, the atomic number decreases by one. The mass number stays the same because a new neutron is created during the loss of the proton.

a) mass number decreases and atomic number decreases, incorrect, Although atomic number decreases, the mass number stays the same because of the creation of a neutron.

b) mass number decreases and atomic number stays the same, incorrect, Mass number stays the same and atomic number decreases.

c) mass number stays the same and atomic number decreases, correct.

d) mass number increases and atomic number increases, incorrect, There is no radioactive decay reaction that increases mass number and atomic number.

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