Problem 10 - Introductory Chemistry Atoms First

Question

Fill in this table: $$ \begin{array}{lcccc} & { }^{14} \mathrm{~N} & \frac{24}{12} \mathrm{Mg} & { }_{11}^{23} \mathrm{Na} & { }^{59} \mathrm{Fe} \\ \hline \text { Mass number } & ? & ? & ? & ? \\ \text { Atomic number } & ? & ? & ? & ? \\ \text { Number of protons } & ? & ? & ? & ? \\ \text { Number of neutrons } & ? & ? & ? & ? \\ \text { Number of electrons } & ? & ? & ? & ? \\ \hline \end{array} $$

Step-by-Step Solution

Answer

The filled table is as follows: $$ \begin{array}{lcccc} & { }^{14} \mathrm{~N} & \frac{24}{12} \mathrm{Mg} & { }_{11}^{23} \mathrm{Na} & { }^{59} \mathrm{Fe} \\\ \hline \text { Mass number } & 14 & 24 & 23 & 59 \\\ \text { Atomic number } & 7 & 12 & 11 & 26 \\\ \text { Number of protons } & 7 & 12 & 11 & 26 \\\ \text { Number of neutrons } & 7 & 12 & 12 & 33 \\\ \text { Number of electrons } & 7 & 12 & 11 & 26 \\\ \hline \end{array} $$

Step 1: Identify Atomic Number, Mass Number, and Chemical Symbol for Each Element

First, let us identify the atomic number (Z), mass number (A), and chemical symbols for each element given in the question. 1) \({ }^{14} \mathrm{~N}\): Here, the chemical symbol is N (Nitrogen) with mass number (A) = 14. The atomic number is not given, so we will need to find the atomic number of Nitrogen from the periodic table, which is 7. 2) \(\frac{24}{12} \mathrm{Mg}\): Here, the chemical symbol is Mg (Magnesium), atomic number (Z) = 12, and mass number (A) = 24. 3) \({ }_{11}^{23} \mathrm{Na}\): Here, the chemical symbol is Na (Sodium), atomic number (Z) = 11, and mass number (A) = 23. 4) \({ }^{59} \mathrm{Fe}\): Here, the chemical symbol is Fe (Iron), with mass number (A) = 59. The atomic number is not given, so we will need to find the atomic number of Iron from the periodic table, which is 26.

Step 2: Fill in the Table

Now that we have identified the atomic number, mass number, and chemical symbol for each element, we can fill in the table. $$ \begin{array}{lcccc} & { }^{14} \mathrm{~N} & \frac{24}{12} \mathrm{Mg} & { }_{11}^{23} \mathrm{Na} & { }^{59} \mathrm{Fe} \\\ \hline \text { Mass number } & 14 & 24 & 23 & 59 \\\ \text { Atomic number } & 7 & 12 & 11 & 26 \\\ \text { Number of protons } & 7 & 12 & 11 & 26 \\\ \text { Number of neutrons } & 7 & 12 & 12 & 33 \\\ \text { Number of electrons } & 7 & 12 & 11 & 26 \\\ \hline \end{array} $$ Remember that the number of neutrons can be calculated by subtracting the atomic number from the mass number (A - Z). Similarly, the number of electrons is equal to the number of protons (Z) for a neutral element.

Key Concepts

Isotopes

Isotopes are variations of the same chemical element that have the same number of protons but different numbers of neutrons. This results in a different mass number for each isotope while retaining the same atomic number and chemical properties. For example, Carbon can exist as Carbon-12, Carbon-13, and Carbon-14, with 6 protons in each but varying in the number of neutrons. Knowing about isotopes is important because:

• They help in radiocarbon dating to determine the age of ancient artifacts.
• Some isotopes are used in medical diagnostics and treatments, like radioactive iodine for thyroid issues.

To learn about specific isotopes, chemists use diagrams and tables that display their differences in neutron count and mass number.

Atomic Number

The atomic number, denoted by the symbol \( Z \), is fundamental in determining the identity of an element. It is the number of protons found in the nucleus of an atom. The atomic number is unique for each element and can be found in the periodic table. For instance:

• Nitrogen has an atomic number of 7, meaning it has 7 protons.
• Magnesium's atomic number is 12, so it contains 12 protons.
• Sodium has 11 protons, as indicated by its atomic number.

The atomic number also affects the element's electronic configuration, dictating how electrons are distributed around the nucleus.

Mass Number

Mass number, or \( A \), is the sum of the number of protons and neutrons in the atomic nucleus. Unlike the atomic number, it is not unique and can vary among isotopes of a single element. It is a whole number and important to remember that:

• It determines the isotope's mass and thus its atomic weight.
• Helps in identifying specific isotopes, for example, \( ^{14}\text{C} \) for Carbon-14.
• For elements like Iron with mass number 59, we deduce that there are 26 protons and use \( A-Z \) to calculate that there are 33 neutrons.

An easy formula to remember: \( A = Z + N \), where \( N \) is the number of neutrons.

Neutrons

Neutrons are subatomic particles found in the atomic nucleus. Unlike protons, they carry no charge and contribute to the atom's mass. To find the number of neutrons in an atom, subtract the atomic number \( Z \) from the mass number \( A \). Neutrons are significant because they:

• Stabilize the nucleus, balancing the repulsive forces between protons.
• Contribute to the mass of an atom significantly.
• Play a role in nuclear reactions and fission processes in energy generation.

For instance, Oxygen (\( A = 16, Z = 8 \)) has 8 neutrons.

Protons

Protons are positively charged particles located in an atom's nucleus. They define the identity of an element through their count equal to the atomic number \( Z \). Each element has a specific number of protons, for example:

• Helium, with an atomic number of 2, has 2 protons.
• Iron's 26 protons give it its place on the periodic table.

Protons are crucial as they:

• Determine the chemical properties and reactions of the element.
• Affect the elements Electronic structure causing changes in chemical behavior.

They are bound within the nucleus through strong nuclear forces, combating the repulsion caused by their positive charges.

Electrons

Electrons are tiny, negatively charged subatomic particles that orbit an atom's nucleus. Their arrangement around the nucleus defines the atom's electron configuration and influences the chemical behavior of an element. Key points about electrons include:

• In a neutral atom, the number of electrons equals the number of protons, balancing its charge.
• They occupy energy levels or shells, filling from lower to higher energies.
• Responsible for the atom's interactions in forming chemical bonds such as ionic or covalent bonds.

Understanding electrons helps clarify why certain elements are reactive, like Sodium, whereas others, such as Neon, are inert.