Question

Draw a diagram of the arrangement of protons, neutrons, and electrons in an atom of each of the following isotopes: (a) \({ }_{3}^{7} \mathrm{Li}\) (b) \({ }_{6}^{13} \mathrm{C}\) (c) \({ }_{8}^{16} \mathrm{O}\) (d) \({ }_{10}^{20} \mathrm{Ne}\)

Short answer

Draw nucleus with protons and neutrons; electrons go in shells: Li has 2+1, C 2+4, O 2+6, Ne 2+8.

Step-by-step solution

Understanding Isotopic Notation

The isotopic notation \( _{Z}^{A}X \) provides information about the atom:- \( Z \) is the atomic number, showing the number of protons.- \( A \) is the mass number, which equals the sum of protons and neutrons.- \( X \) is the chemical symbol of the element.- Number of electrons in a neutral atom equals the number of protons.

Determine Protons, Neutrons, and Electrons for (a) \( _{3}^{7} ext{Li} \)

For lithium with isotopic notation \( _{3}^{7} ext{Li} \):- The atomic number \( Z = 3 \) provides 3 protons.- The mass number \( A = 7 \) gives total of 7 - 3 = 4 neutrons.- A neutral atom has 3 electrons.

Diagram Arrangement for (a) \( _{3}^{7} ext{Li} \)

Based on the numbers: - The nucleus contains 3 protons and 4 neutrons. - Arrange the electrons (3) around the nucleus, typically with 2 in the first shell and 1 in the second.

Determine Protons, Neutrons, and Electrons for (b) \( _{6}^{13} ext{C} \)

For carbon with isotopic notation \( _{6}^{13} ext{C} \):- The atomic number \( Z = 6 \) provides 6 protons.- The mass number \( A = 13 \) gives total of 13 - 6 = 7 neutrons.- A neutral atom has 6 electrons.

Diagram Arrangement for (b) \( _{6}^{13} ext{C} \)

Based on the numbers: - The nucleus contains 6 protons and 7 neutrons. - Arrange the electrons (6) around the nucleus with 2 in the first shell and 4 in the second.

Determine Protons, Neutrons, and Electrons for (c) \( _{8}^{16} ext{O} \)

For oxygen with isotopic notation \( _{8}^{16} ext{O} \):- The atomic number \( Z = 8 \) provides 8 protons.- The mass number \( A = 16 \) gives total of 16 - 8 = 8 neutrons.- A neutral atom has 8 electrons.

Diagram Arrangement for (c) \( _{8}^{16} ext{O} \)

Based on the numbers: - The nucleus contains 8 protons and 8 neutrons. - Arrange the electrons (8) around the nucleus with 2 in the first shell and 6 in the second.

Determine Protons, Neutrons, and Electrons for (d) \( _{10}^{20} ext{Ne} \)

For neon with isotopic notation \( _{10}^{20} ext{Ne} \):- The atomic number \( Z = 10 \) provides 10 protons.- The mass number \( A = 20 \) gives total of 20 - 10 = 10 neutrons.- A neutral atom has 10 electrons.

Diagram Arrangement for (d) \( _{10}^{20} ext{Ne} \)

Based on the numbers: - The nucleus contains 10 protons and 10 neutrons. - Arrange the electrons (10) around the nucleus with 2 in the first shell and 8 in the second.

Key concepts

Isotopes

Atoms of the same element can have different numbers of neutrons, leading to variations called isotopes. Isotopes share the same number of protons but differ in their mass numbers due to the different number of neutrons.
Think of isotopes as siblings within the same family. They have similar features, like the same element or chemical properties because they have the same number of protons, but they differ in weight due to the varying neutron counts.
For instance, let's consider lithium, represented by the isotopic notation \( _{3}^{7}\text{Li} \):

• This tells us it has 3 protons, making it lithium's version.
• It contains 4 neutrons, calculated by subtracting the atomic number from the mass number \((7 - 3)\).
• Thus, even with the same element identity, isotopes bring about subtle differences, often crucial in scientific experiments and applications, like carbon dating.

Protons

Protons are a fundamental component of an atom's nucleus. They are positively charged and significantly determine the identity of an element, being equal to the atomic number.
Every element on the periodic table has a unique number of protons. For example, hydrogen always contains one proton, no matter which isotope you encounter.

• Protons have a charge of +1 and a relative mass of 1 atomic mass unit (amu).
• They are found in the nucleus alongside neutrons, adding to the atom's mass.
• In isotopic notation, the number of protons is represented by \( Z \), the atomic number.
• For lithium \( _{3}^{7}\text{Li} \), the number 3 indicates there are 3 protons present.

The stability of an atom, its interactions, and its placement in the periodic table start with this fundamental particle.

Neutrons

Neutrons play an essential role in the nucleus of an atom, providing stability and contributing to the atom's mass without affecting its charge, since they are neutral.
While protons define the element's identity, neutrons impact the mass of the element and can create various isotopes for the same element. A variation in the number of neutrons leads to different isotopes.

• Neutrons have a relative mass roughly equal to protons, about 1 amu.
• They do not carry any charge, hence they contribute to the stability of the atom by preventing protons, which repel each other due to like charges, from flying apart.
• The difference in neutron number among isotopes can elucidate features like radioactivity or stability.
• For example, in the isotope \( _{6}^{13}\text{C} \), carbon has 7 neutrons \((13 - 6)\).

Electrons

Electrons are the lightweight, negatively charged particles that orbit the nucleus of an atom in areas called electron shells. These little particles play a crucial role in chemical bonding and reactions.
Each electron has a charge of \(-1\) and contributes practically no mass compared to protons and neutrons. Since atoms are typically neutral, a hydrogen atom with one proton will also have one electron.

• Electrons are vital in the formation of chemical bonds and define the chemical reactivity of substances.
• Each shell can hold a specific number of electrons. For low atomic numbers, the first shell can hold up to 2 electrons, and the second can accommodate up to 8 electrons.
• In lithium \( _{3}^{7}\text{Li} \), there are 3 electrons arranged as 2 in the first shell and 1 in the second shell.
• The arrangement of electrons in shells relates to an atom's energy states and plays a substantial role in determining an element's chemical properties.

Isotopic Notation

Isotopic notation offers a clear and concise way to represent isotopes of elements, encapsulating critical information about an atom's subatomic structure. It is formatted as \( _{Z}^{A}X \), where each symbol has a specific meaning.
This notation helps scientists, educators, and students quickly identify and differentiate isotopes within the same element family.

• \( Z \): The atomic number, representing the number of protons in the nucleus of an atom, and defines what element it is.
• \( A \): The mass number, which is the sum of protons and neutrons, giving insight into the isotope's composition.
• \( X \): The chemical symbol of the element, typically found on the periodic table and commonly known by its alphabetic label, such as \(\text{Li}\) for lithium.
• Using isotopic notation allows quick calculation of the number of neutrons by subtracting \(Z\) from \(A\).

Understanding isotopic notation is crucial in fields such as nuclear physics, chemistry, and environmental science.