Atomic Basics
Isotopes & Atomic Mass
Radioactivity
Nuclear Decay Equations
Half-Life
100

This subatomic particle has a negative charge and a negligible mass. 

Electron

100

This is the word used to refer to atoms of the same element that have different numbers of neutrons. 

Isotopes.

100

Which type of radiation has the highest energy, no mass or charge, and can pass through most materials?

Gamma radiation

100

What is the symbol used to represent gamma radiation?

00Y

100

The time that it takes for half of a radioactive substance to decay is called ________.

Half-life

200

These subatomic particles are located in the nucleus of an atom, and are sometimes referred to as "nucleons". 

Protons and neutrons

200

Isotopes of Potassium: K-39, K-40, K-41. Its atomic mass is 39.09. Which isotope is most abundant?

K-39

200

Alpha particles are made up of these two subatomic particles. 

2 protons, 2 neutrons (just like a Helium nucleus)

200

What happens to the mass number when an atom emits an alpha particle?

It decreases by 4. 

200

12 grams of a radioactive isotope starts to decay. How much will be left after two half-lives?

3 grams

300

Why does changing the number of electrons not change the element’s identity?

An element's identity is based on its number of protons, not electrons. 

300

How is the average atomic mass of an element calculated?

% abundance expressed as a decimal x mass number, then add these up for all isotopes of that element. 
300

Einsteinium-252 undergoes alpha decay. Predict the products of this reaction. 

42He and 24897Bk

300

An isotope emits a beta particle. Predict the new element if the original isotope was Potassium-39.

Calcium-39

300

A 160 g sample decays to 20 g. If the half-life of the isotope is 2 hours, how long did it take to reach 20 g?

6 hours

400

If an atom has 15 protons, 18 neutrons, and 15 electrons, what is its mass number?

33
400

An element has a mass number of 80, and has 41 neutrons. What element is it?

80 - 41 = 39 protons, Yttrium

400

An isotope of Polonium-210 undergoes beta decay. Explain how both the atomic number and mass number will change. 

The mass number will remain at 210, and the atomic number will increase by 1. 

400

A radioactive isotope undergoes beta decay and emits a gamma ray immediately afterward. Explain what happens to the atomic number and mass number during each step.

During beta decay: a neutron converts into a proton, so the atomic number increases by 1, mass number stays the same.

During gamma emission: the nucleus releases excess energy; neither atomic number nor mass number changes.

400

A 200 g sample of an isotope decays to 25 g. How many half-lives have passed?

3 half-lives

500

Give an example of a pair of isotopes of the same element, and explain why they have different mass numbers.

Answers may vary: Carbon-12 and Carbon-14. They have different numbers of neutrons, so their mass numbers are different.

500

Given these isotopes of element X:
50.69% at 79 amu and 49.31% at 81 amu — calculate the average atomic mass.

79.996 amu

500

Explain why alpha particles are easily blocked by thin materials like paper/tissues. 

Alpha particles are relatively massive compared to beta particles or gamma rays-- they move more slowly and are easier to stop. 

500

Lead-212 undergoes alpha decay AND gamma decay. Write the complete nuclear decay equation. 

21282Pb --> 42He + 00Y + 20880Hg

500

Iodine-131 has a half-life of 8 days. If you start with 32 g, how much remains after 32 days? Show the calculation step by step.

1st half-life: 32 → 16 g

2nd half-life: 16 → 8 g

3rd half-life: 8 → 4 g

4th half-life: 4 → 2 g




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