Isotope Calculations

If a rock sample contains 50% parent isotopes and 50% daughter isotopes, how many half-lives have passed?

• 0.5

• 1

• 2

• 3

A scientist finds a sample with a parent-to-daughter isotope ratio of 25:75. How many half-lives have passed?

• 1

• 4

• 3

• 2

What does the term "half-life" mean in radioactive dating?

• The time it takes for half of the parent isotope to decay into daughter isotopes

• The time it takes for all isotopes in a sample to decay

• The average age of a fossil sample

• The amount of time a radioactive element stays stable

Tags

NGSS.HS-PS1-8

If the half-life of a parent isotope is 2 billion years, and three half-lives have passed, how old is the sample?

• 2 billion years

• 4 billion years

• 6 billion years

• 8 billion years

Why is mathematical modeling important in radioactive dating?

• It allows scientists to observe isotopes directly in real time.

• It simplifies calculations for determining the age of a sample.

• It eliminates the need for experimental data.

• It helps measure the speed of chemical reactions.

What happens to the daughter isotope count as the parent isotope decays?

• It decreases

• It remains constant

• It fluctuates randomly

• It increases

Tags

NGSS.HS-PS1-8

What is the average atomic mass for thallium, Tl, if there are two isotopes with the following masses and abundances? Tl-203 has a mass of 203 amu with an abundance of 29.5 % Tl-205 has a mass of 205 amu with an abundance of 70.5 %

• 203.12 amu

• 204.31 amu

• 204.41 amu

• 204.0 amu

A sample of cesium is 75% Cs-133, 20% Cs-132, and 5% Cs-134. What is the average atomic mass?

• 132.97 amu

• 133.00 amu

• 133.16 amu

• 132.85 amu

4.35% of all X atoms have a mass of 39.946 amu. 83.79% have a mass of 41.941 amu, 9.50% have a mass of 42.941 amu, and 2.36% have a mass of 43.939 amu. What is the average atomic mass of atom X?

• 41.97 amu

• 42.19 amu

• 10.43 amu

• 40.04 amu

Calculate the average atomic mass of the element iron (Fe) using the following data:

[Isotope / % abundance]

[Iron 54 / 6% ] [Iron 56 / 92% ] [ Iron 57 / 2% ]

• 53.7 amu

• 54.9 amu

• 5592.0 amu

• 55.9 amu