Question

directions: complete the following chart

isotope	mass number	number of protons	number of neutrons
$ra^{226}_{88}$	13.	14.	15.

directions: fill in the blank

1. what is one medical use of radioactive materials?
2. the time it takes for half of a radioactive substance to decay is called______.
3. the process of atomic nuclei joining to release energy is called______.
4. the basic building blocks of an atom______.
5. an atom that is radioactive is called______.

Explanation:

Step1: Recall mass - number formula

The mass number ($A$) of an isotope is the sum of the number of protons ($p$) and neutrons ($n$), i.e., $A=p + n$.

Step2: Calculate for $Ra$

For $Ra$, if we assume the mass - number formula. But there is a mistake in the problem as $Al$ has atomic number 13 (number of protons), not 11. Assuming it's a different element with 11 protons (sodium, $Na$). For $Ra$ (radium), the atomic number of $Ra$ is 88. So the number of protons ($p$) = 88. If we know the mass - number formula $A=p + n$, and assume we want to find the mass - number when $p = 88$ and say $n=138$ (a common isotope of $Ra$ has mass - number 226, so $n=226 - 88=138$). Then the mass - number $A = 88+138=226$.

Step3: Answer medical use question

One medical use of radioactive substances is cancer treatment (radiation therapy).

Step4: Define half - life

The time it takes for half of a radioactive substance to decay is called half - life.

Step5: Define nuclear fusion

The process of atomic nuclei joining to release energy is called nuclear fusion.

Step6: Identify basic building blocks of an atom

The basic building blocks of an atom are protons, neutrons, and electrons.

Step7: Define radioactive atom

An atom that is radioactive is called a radioisotope.

Answer:

1. 226
2. 88
3. 138
4. Cancer treatment (radiation therapy)
5. Half - life
6. Protons, neutrons, and electrons
7. Radioisotope