Problem 7 - Chemistry and Chemical Reactivity

Question

How many electrons, protons, and neutrons are there in each of the following atoms? (a) magnesium- \(24,^{24} \mathrm{Mg}\) (b) tin- \(119,^{119} \mathrm{Sn}\) (c) thorium-232, \(^{232} \mathrm{Th}\) (d) carbon- \(13,^{13} \mathrm{C}\) (e) copper-63, \(^{63} \mathrm{Cu}\) (f) bismuth- \(205,^{205} \mathrm{Bi}\)

Step-by-Step Solution

Answer

Magnesium: 12p, 12n, 12e; Tin: 50p, 69n, 50e; Thorium: 90p, 142n, 90e; Carbon: 6p, 7n, 6e; Copper: 29p, 34n, 29e; Bismuth: 83p, 122n, 83e.

Step 1: Understand Atomic Composition

Atoms consist of protons, neutrons, and electrons. The number of protons defines the element and equals the atomic number. The number of electrons equals the number of protons for neutral atoms. Neutrons can be found by subtracting the atomic number from the mass number.

Step 2: Determine Protons and Electrons

For each element: (a) Magnesium ( ^{24} ext{Mg} ) has 12 protons (atomic number 12). (b) Tin ( ^{119} ext{Sn} ) has 50 protons (atomic number 50). (c) Thorium ( ^{232} ext{Th} ) has 90 protons (atomic number 90). (d) Carbon ( ^{13} ext{C} ) has 6 protons (atomic number 6). (e) Copper ( ^{63} ext{Cu} ) has 29 protons (atomic number 29). (f) Bismuth ( ^{205} ext{Bi} ) has 83 protons (atomic number 83). The number of electrons equals the number of protons for each element because they are neutral atoms.

Step 3: Calculate Neutrons

Subtract the atomic number (protons) from the atomic mass number for each element to find the neutrons: (a) Magnesium: 24 - 12 = 12 neutrons (b) Tin: 119 - 50 = 69 neutrons (c) Thorium: 232 - 90 = 142 neutrons (d) Carbon: 13 - 6 = 7 neutrons (e) Copper: 63 - 29 = 34 neutrons (f) Bismuth: 205 - 83 = 122 neutrons.

Step 4: Summary of Particles

Summarize the number of protons, neutrons, and electrons: (a) Magnesium-24: 12 protons, 12 neutrons, 12 electrons (b) Tin-119: 50 protons, 69 neutrons, 50 electrons (c) Thorium-232: 90 protons, 142 neutrons, 90 electrons (d) Carbon-13: 6 protons, 7 neutrons, 6 electrons (e) Copper-63: 29 protons, 34 neutrons, 29 electrons (f) Bismuth-205: 83 protons, 122 neutrons, 83 electrons.

Key Concepts

Protons

Protons are positively charged particles found in the nucleus of an atom. Each element on the periodic table has a unique number of protons. This number is known as the atomic number. The atomic number is essential because it determines the identity of the element. For example, every atom of magnesium has 12 protons, which is why its atomic number is 12. This is true for all elements:

• Tin has 50 protons, giving it the atomic number 50.
• Thorium has 90 protons, leading to an atomic number of 90.
• Carbon contains 6 protons, corresponding to an atomic number of 6.
• Copper has an atomic number of 29 due to its 29 protons.
• Bismuth features 83 protons, resulting in an atomic number of 83.

Protons play a crucial role in the stability and chemistry of an atom. They determine the element's properties and participate in nuclear forces, which bind the nucleus together. Understanding the number of protons helps in identifying the element and predicting its chemical behavior.

Neutrons

Neutrons are neutral particles, meaning they have no electric charge and reside in the atom's nucleus alongside protons. Neutrons, together with protons, make up almost all of an atom's mass. While protons define the element, neutrons can vary in number without changing the type of element. This can lead to the existence of isotopes.

• To find the number of neutrons, subtract the atomic number (protons) from the mass number.
• For example, magnesium-24 means the mass number is 24. Subtract 12 protons (the atomic number) and you get 12 neutrons.
• Similarly, tin-119 has 50 protons and 69 neutrons (119-50).
• Thorium-232 is composed of 90 protons and 142 neutrons (232-90).
• In carbon-13, 6 protons are accompanied by 7 neutrons (13-6).
• Copper-63 comprises 29 protons and 34 neutrons (63-29).
• Bismuth-205 contains 83 protons and 122 neutrons (205-83).

These isotopes hold distinctive properties. They can affect the atom's stability and participate in nuclear reactions, like those used in medicine or energy production.

Electrons

Electrons are tiny, negatively charged particles orbiting the atom's nucleus. In a neutral atom, the number of electrons equals the number of protons, ensuring the electrical neutrality of the atom. The electron configuration greatly influences the chemical properties and reactions of the element.

• Each element in its neutral state has the same number of electrons as its protons.
• For magnesium with 12 protons, there are 12 electrons.
• Tin’s 50 electrons match its 50 protons.
• Thorium has 90 electrons orbiting around its nucleus of 90 protons.
• Carbon features 6 electrons for its 6 protons.
• Copper displays 29 electrons and thus 29 protons.
• Bismuth mirrors its 83 protons with 83 electrons.

Electrons are pivotal to the formation of chemical bonds. They are involved in various interactions, such as ionic and covalent bonding, dictating how atoms combine to form molecules. Their arrangement, or electron configuration, determines how atoms bond with each other, dictating the element's chemical nature.