Question

activity a: subatomic particles
get the gizmo ready:

• use the arrows to create an atom with two protons, two neutrons, and two electrons.
• turn on show element name.

question: what are the properties of protons, neutrons, and electrons?

1. observe: turn on show element symbol and element notation. three numbers surround the element symbol: the mass number (a), electrical charge (no number is displayed if the atom is neutral), and the atomic number (z).
2. investigate: watch how the numbers change as you add or remove particles.

a. which number is equal to the number of protons in the atom?
b. how can you calculate the number of neutrons (n) in an atom?
c. which particle (proton, neutron, or electron) has a positive charge?
no charge at all?
negative charge?

1. analyze: an isotope is an alternative form of an element. each isotope of an element has the same number of protons, but a different number of neutrons. the isotope is represented by the atomic symbol and mass number, such as he - 4. some isotopes are stable, while others are radioactive, which means the atoms decay over time and emit radiation.

a. what are the stable isotopes of carbon?
b. what are the stable isotopes of nitrogen?
c. list two radioactive isotopes of oxygen:

1. practice: use the gizmo to answer the following questions.

a. how many electrons are in a neutral atom of lithium?
b. how many neutrons are in an atom of mg - 25?
c. what is the mass number of an atom with 5 protons and 7 neutrons?
d. when an atom is charged, it is called an ion. how many electrons are in o²⁻?
e. how many electrons are in mg²⁺?

Explanation:

Step1: Recall atomic number definition

The atomic number (Z) is equal to the number of protons in an atom.

Step2: Recall neutron - mass number relationship

The number of neutrons (N) in an atom is calculated by subtracting the atomic number (Z) from the mass number (A), i.e., $N = A - Z$.

Step3: Recall particle charges

Protons have a positive charge, neutrons have no charge, and electrons have a negative charge.

Step4: Recall stable carbon isotopes

The stable isotopes of carbon are carbon - 12 and carbon - 13.

Step5: Recall stable nitrogen isotopes

The stable isotopes of nitrogen are nitrogen - 14 and nitrogen - 15.

Step6: Recall radioactive oxygen isotopes

Two radioactive isotopes of oxygen are oxygen - 13 and oxygen - 15.

Step7: Recall lithium electron number

Lithium (Li) has an atomic number of 3. In a neutral atom, the number of electrons is equal to the number of protons. So, a neutral atom of lithium has 3 electrons.

Step8: Recall Mg - 25 neutron number

Magnesium (Mg) has an atomic number of 12. For Mg - 25, the mass number (A) is 25. Using $N=A - Z$, we have $N = 25- 12=13$ neutrons.

Step9: Recall mass number calculation

The mass number (A) is the sum of the number of protons and neutrons. For an atom with 5 protons and 7 neutrons, $A=5 + 7=12$.

Step10: Recall oxygen ion electron number

Oxygen has an atomic number of 8. In $O^{2 - }$, it has gained 2 electrons. So the number of electrons is $8 + 2=10$.

Step11: Recall magnesium ion electron number

Magnesium has an atomic number of 12. In $Mg^{2+}$, it has lost 2 electrons. So the number of electrons is $12-2 = 10$.

Answer:

A. Atomic number
B. $N = A - Z$
C. Proton; Neutron; Electron

1. A. Carbon - 12, Carbon - 13

B. Nitrogen - 14, Nitrogen - 15
C. Oxygen - 13, Oxygen - 15

1. A. 3

B. 13
C. 12
D. 10
E. 10