Question

Complete the following table for the three naturally occurring isotopes of silicon, the major component in computer chips: $$ \begin{array}{|l|c|c|c|} \hline & \multicolumn{3}{|c|} {\text { Isotope }} \\ \hline & { }^{28} \mathrm{Si} & { }_{14}^{29} \mathrm{Si} & { }_{14}^{30} \mathrm{Si} \\ \hline \text { Number of protons } & & & \\ \hline \text { Number of neutrons } & & & \\ \hline \text { Number of electrons } & & & \\ \hline \text { Atomic number } & & & \\ \hline \text { Mass number } & & & \\ \hline \end{array} $$

Short answer

All isotopes of silicon have 14 protons and 14 electrons. The number of neutrons is 14 for \({ }^{28} \mathrm{Si}\), 15 for \({ }_{14}^{29} \mathrm{Si}\), and 16 for \({ }_{14}^{30} \mathrm{Si}\).

Step-by-step solution

Identify the number of protons (atomic number)

For all isotopes of silicon, the number of protons is the same since they are the same element. Silicon has an atomic number (Z) of 14, meaning each silicon isotope has 14 protons.

Determine the number of neutrons

The number of neutrons can be found by subtracting the atomic number (number of protons) from the mass number. For \({ }^{28} \mathrm{Si}\): \, \, 28 - 14 = 14 \ neutrons\For \({ }_{14}^{29} \mathrm{Si}\): \, \, 29 - 14 = 15 \ neutrons\For \({ }_{14}^{30} \mathrm{Si}\): \, \, 30 - 14 = 16 \ neutrons\

Determine the number of electrons

In a neutral atom, the number of electrons equals the number of protons. Thus, each isotope of silicon has 14 electrons.

State the atomic number

As identified in Step 1, the atomic number of each silicon isotope is 14.

State the mass number

The mass number is the sum of protons and neutrons for each isotope.For \({ }^{28} \mathrm{Si}\): Mass number = 28\For \({ }_{14}^{29} \mathrm{Si}\): Mass number = 29\For \({ }_{14}^{30} \mathrm{Si}\): Mass number = 30

Key concepts

Number of Protons

The number of protons in an atom is crucial because it defines the element. This is also known as the atomic number.
For silicon, regardless of the isotope, each atom always has 14 protons because the atomic number of silicon is 14. This is consistent for all silicon isotopes mentioned:

• \( ^{28} \mathrm{Si} \)
• \( ^{29} \mathrm{Si} \)
• \( ^{30} \mathrm{Si} \)

So, whenever you see an element in the periodic table, remember that its atomic number tells you the number of protons it has.

Number of Neutrons

The number of neutrons in an atom can vary even within the same element. This variance causes different isotopes.
To calculate the number of neutrons, subtract the atomic number from the mass number. Here's how it works for silicon isotopes:

• For \( ^{28} \mathrm{Si}\): Neutrons = 28 - 14 = 14
• For \( ^{29} \mathrm{Si}\): Neutrons = 29 - 14 = 15
• For \( ^{30} \mathrm{Si}\): Neutrons = 30 - 14 = 16

As you can see, isotopes have different numbers of neutrons, but the same number of protons.

Number of Electrons

In neutral atoms, the number of electrons equals the number of protons. This maintains the electrical neutrality of the atom. For silicon and its isotopes, this means:

• Each silicon isotope has 14 electrons.
• This matches the 14 protons in the nucleus.

It's an essential rule to remember: the number of electrons in a neutral atom always equals the number of protons.

Atomic Number

The atomic number of an element is a fundamental property. It represents the number of protons in the nucleus of an atom. For silicon:

• The atomic number (Z) is 14.
• This applies to all its isotopes.

The atomic number is what identifies the element and separates it from others in the periodic table.

Mass Number

The mass number is the total count of protons and neutrons in an atom's nucleus. It is important for distinguishing between different isotopes of an element. For silicon isotopes:

• For \( ^{28} \mathrm{Si}\): The mass number is 28.
• For \(^{29} \mathrm{Si}\): The mass number is 29.
• For \(^{30} \mathrm{Si}\): The mass number is 30.

Remember, the mass number varies with different isotopes due to changes in the number of neutrons, but the proton count remains the same.