In the following diagrams, A represents a radioactive isotope that decays into a new isotope, X. Each circle represents 1 mmol of atoms. |

t = 0: |

t = 25.0 s: |

Over the first 25.0 s, what is the disintegration rate of A? |

▸ 0.120 disintegrations per second

▸

1.81 × 10^{21} disintegrations per second

▸ 3.00 disintegrations per second

▸

7.23 × 10^{19} disintegrations per second

▸

1.38 × 10^{–20} disintegrations per second