Question

Indicate the number of protons and neutrons in the following nuclei: (a) \({ }_{53}^{129} \mathrm{I}\), (b) \({ }^{138} \mathrm{Ba}\), (c) neptunium-237.

Short answer

(a) Iodine-129: 53 protons, 76 neutrons; (b) Barium-138: 56 protons, 82 neutrons; (c) Neptunium-237: 93 protons, 144 neutrons.

Step-by-step solution

(Find atomic number for each element)

(Using the periodic table or your knowledge about elements, find the atomic number (number of protons) for iodine, barium, and neptunium, keeping in mind that the atomic number is given as a subscript in the notation.)

(Calculate the number of neutrons for each element)

(To find the number of neutrons in each element, subtract the atomic number (number of protons) from the mass number (given as a superscript or in the element's name).)

(a) Find the protons and neutrons in Iodine-129)

(We are given the notation \({}_{53}^{129} \mathrm{I}\). The atomic number is 53, so there are 53 protons. The mass number is 129, so to find the neutrons, we subtract the atomic number from the mass number: \(129 - 53 = 76\). Therefore, there are 76 neutrons in Iodine-129.)

(b) Find the protons and neutrons in Barium-138)

(For Barium-138, only the mass number is given, so we must find the atomic number from the periodic table. Barium has an atomic number of 56, which means it has 56 protons. Now subtract the atomic number from the mass number to find the neutrons: \(138 - 56 = 82\). Therefore, there are 82 neutrons in Barium-138.)

(c) Find the protons and neutrons in Neptunium-237)

(For Neptunium-237, only the mass number is given, so we must find the atomic number from the periodic table. Neptunium has an atomic number of 93, which means it has 93 protons. Now subtract the atomic number from the mass number to find the neutrons: \(237 - 93 = 144\). Therefore, there are 144 neutrons in Neptunium-237.)

Key concepts

Atomic Number

The atomic number is one of the most fundamental aspects of an element's identity in chemistry. It is denoted by the letter 'Z' and represents the number of protons found in the nucleus of an atom. Since protons carry a positive charge, the atomic number also determines the charge of the nucleus and ultimately the element itself. For example, when we look at an element such as iodine, represented as \( {}_{53}^{129} \mathrm{I} \), the atomic number is the subscript 53, which tells us that each iodine atom contains 53 protons.

Understanding the atomic number is not only crucial for identifying the element but also serves as a guide for locating elements in the periodic table, as they are arranged in increasing order of their atomic numbers. This straightforward yet vital concept lays the groundwork for exploring and comprehending the diversity of elements in the universe.

Neutrons Calculation

Calculating the number of neutrons in an atom's nucleus is a necessary skill for students delving into chemistry and atomic structure. Neutrons, along with protons, make up the mass of the nucleus and thus play a critical role in the overall mass of the atom. Unlike protons, the number of neutrons is not fixed for a given element and can vary, leading to the formation of isotopes.

To calculate the number of neutrons, you will need to know two things: the atomic number \(Z\) (number of protons) and the mass number \(A\) (total number of protons and neutrons). The neutron number \(N\) is the difference between the mass number and the atomic number:\[ N = A - Z \]. For instance, with iodine-129 (\( {}_{53}^{129} \mathrm{I} \)), we have 129 as the mass number and 53 as the atomic number. By subtracting, \(129 - 53 = 76\), we find out that there are 76 neutrons in the nucleus.

Periodic Table

The periodic table is the map of the elements, organizing them by increasing atomic number and grouping them into categories that share similar properties. Every element in the periodic table is arranged in a way that provides a wealth of information at a glance. Elements are listed in rows called periods and columns known as groups or families.

For instance, by locating barium on the periodic table, we can instantly find out that it's an alkaline earth metal, as it's in group 2, and has an atomic number of 56. This is extremely helpful when barium is represented as \( {}^{138}\mathrm{Ba} \), with no subscript - the periodic table lets us easily find that missing atomic number. Furthermore, the position of an element in the periodic table provides insights into its chemical behavior, reactivity, and the types of chemical bonds it can form. It's a powerful tool that transcends beyond mere classification, it's the chemist's best guide for predicting and understanding the elements and their interactions.