Problem 26 - Chemistry: An Atoms-Focused Approach

Question

How many protons, neutrons, and electrons are there in the following atoms? (a) \(^{11} \mathrm{B} ;\) (b) \(^{19} \mathrm{F} ;\) (c) \(^{131} \mathrm{I}\); (d) \(^{222} \mathrm{Rn}\)

Step-by-Step Solution

Answer

Question: Determine the number of protons, neutrons, and electrons for the given elements: \(^{11} \mathrm{B}\), \(^{19} \mathrm{F}\), \(^{131} \mathrm{I}\), and \(^{222} \mathrm{Rn}\). Answer: \(^{11} \mathrm{B}\) has 5 protons, 6 neutrons, and 5 electrons. \(^{19} \mathrm{F}\) has 9 protons, 10 neutrons, and 9 electrons. \(^{131} \mathrm{I}\) has 53 protons, 78 neutrons, and 53 electrons. \(^{222} \mathrm{Rn}\) has 86 protons, 136 neutrons, and 86 electrons.

Step 1: Identify atomic numbers

First, identify the atomic number (number of protons) for each given element by checking the periodic table of elements. - B (Boron) has an atomic number of 5 - F (Fluorine) has an atomic number of 9 - I (Iodine) has an atomic number of 53 - Rn (Radon) has an atomic number of 86 Since the number of electrons equals the number of protons in an atom, we can note the number of electrons for each atom as well.

Step 2: Calculate the number of neutrons

Now, use the given mass numbers of each atom and their atomic numbers to find the number of neutrons: For an element X, Neutrons = Mass number - Atomic number (a) For \(^{11} \mathrm{B}\): - Number of protons: 5 - Number of electrons: 5 - Number of neutrons: 11 - 5 = 6 (b) For \(^{19} \mathrm{F}\): - Number of protons: 9 - Number of electrons: 9 - Number of neutrons: 19 - 9 = 10 (c) For \(^{131} \mathrm{I}\): - Number of protons: 53 - Number of electrons: 53 - Number of neutrons: 131 - 53 = 78 (d) For \(^{222} \mathrm{Rn}\): - Number of protons: 86 - Number of electrons: 86 - Number of neutrons: 222 - 86 = 136

Step 3: Summary

The protons, neutrons, and electrons in the given atoms are: (a) \(^{11} \mathrm{B}\) has 5 protons, 6 neutrons, and 5 electrons. (b) \(^{19} \mathrm{F}\) has 9 protons, 10 neutrons, and 9 electrons. (c) \(^{131} \mathrm{I}\) has 53 protons, 78 neutrons, and 53 electrons. (d) \(^{222} \mathrm{Rn}\) has 86 protons, 136 neutrons, and 86 electrons.

Key Concepts

Atomic Number

The atomic number is a fundamental characteristic of an element that tells us the number of protons within an atom's nucleus. Protons are positively charged particles, and they define the identity of the element. For example, with an atomic number of 5, Boron always contains 5 protons. This number is specific to each element. You can conveniently locate it on the periodic table, typically found as a small whole number. This number also matches the number of electrons in a neutral atom, ensuring the atom has no overall charge. It's a unique identifier for each element you encounter in chemistry.

Mass Number

The mass number of an atom provides important insight into its overall mass. It is determined by the sum of protons and neutrons in the nucleus of the atom.
For example, for Boron (\(^{11} \text{B}\)), the mass number is 11. Mass number isn't listed on the periodic table and can vary for different isotopes of an element. Isotopes are atoms with the same number of protons but different numbers of neutrons. Despite minor differences in the nucleus, isotopes maintain the elemental identity because of their constant number of protons.

Protons, Neutrons, and Electrons

To understand atoms, it's vital to comprehend their subatomic particles: protons, neutrons, and electrons.

• **Protons** are positively charged particles located in the nucleus, influencing the element's identity as shown by the atomic number.
• **Neutrons** are neutral particles also residing in the nucleus. The number of neutrons affects the atom’s mass and stability but not its elemental identity.
• **Electrons** are negatively charged particles orbiting the nucleus, balancing the positive charge of the protons in a neutral atom.

In the examples you studied, these particles add up to make up the unique identities and properties of various atoms.

Periodic Table

The periodic table is a crucial tool in chemistry that organizes all known elements based on their atomic number, electron configurations, and recurring chemical properties. Elements are arranged in order of increasing atomic number, starting from Hydrogen.
Each element has its unique place on this table. This arrangement reveals trends and allows predictions of element behavior, chemical reactions, and bonds. For example, the table helps us instantly identify that Boron is group 13, period 2, indicating its similarities with other elements in the same group or family.
It is an invaluable resource for identifying atomic numbers, determining element properties, and understanding the relationships between different elements.