When a beta particle is released from the nucleus of an atom:

the number of electrons in the atom decreases by one

the number of electrons in the atom increases by one as the beta particle leaves the nucleus and joins the valence electrons

the mass number of the atom remains the same

the mass number of the atom decreases

Question

When a beta particle is released from the nucleus of an atom:

		
the number of electrons in the atom decreases by one
 		
the number of electrons in the atom increases by one as the beta particle leaves the nucleus and joins the valence electrons
 		
the mass number of the atom remains the same
 		
the mass number of the atom decreases

anonymous · Answer

the mass number of the atom decreases

jfraser · Answer

mass number remains the same. A beta particle is formed when a neutron decays into a proton and an electron, conserving charge
$$^{14}_6C \space \rightarrow \space  ^0_{-1} \beta \space  + \space ^{14}_7N$$

anonymous · Answer

okay . 
I just wanted to know if my answer to this question is right.
A 10.0-gram sample of strontium-90 has a half-life of 29 years. How many half-lives will have passed before the sample is reduced to 2.50 grams?

is it 2?

jfraser · Answer

2.5g is 1/4 of 10g. 1/4 is (1/2)^2, so 2 half-lives have passed. You are correct

anonymous · Answer

okay thanks.