Question

How many protons, neutrons, and electrons are in each of the following atoms or ions? a. \(_{12}^{24} \mathrm{Mg}\) b. \(_{12}^{24} \mathrm{Mg}^{2+}\) c. \(_{27}^{59} \mathrm{Co}^{2+}\) d. \(_{27}^{59} \mathrm{Co}^{3+}\) e. \(_{2}^{59} \mathrm{Co}\) f. \(_{34}^{79} \mathrm{Se}\) g. \(_{34}^{79} \mathrm{Se}^{2-}\) h. \(_{28}^{63} \mathrm{Ni}\) i. \(_{28}^{59} \mathrm{Ni}^{2+}\)

Short answer

a. \(_{12}^{24} \mathrm{Mg}\): 12 protons, 12 neutrons, 12 electrons b. \(_{12}^{24} \mathrm{Mg}^{2+}\): 12 protons, 12 neutrons, 10 electrons c. \(_{27}^{59} \mathrm{Co}^{2+}\): 27 protons, 32 neutrons, 25 electrons d. \(_{27}^{59} \mathrm{Co}^{3+}\): 27 protons, 32 neutrons, 24 electrons e. \(_{2}^{59} \mathrm{Co}\): Incorrect atom notation f. \(_{34}^{79} \mathrm{Se}\): 34 protons, 45 neutrons, 34 electrons g. \(_{34}^{79} \mathrm{Se}^{2-}\): 34 protons, 45 neutrons, 36 electrons h. \(_{28}^{63} \mathrm{Ni}\): 28 protons, 35 neutrons, 28 electrons i. \(_{28}^{59} \mathrm{Ni}^{2+}\): 28 protons, 31 neutrons, 26 electrons

Step-by-step solution

1. Determine Protons for Each Atom or Ion#a.

Protons are equal to the atomic number (Z) for each given atom or ion. Protons do not change when there's a charge. a. Protons in \(_{12}^{24} \mathrm{Mg}\): Z = 12 b. Protons in \(_{12}^{24} \mathrm{Mg}^{2+}\): Z = 12 c. Protons in \(_{27}^{59} \mathrm{Co}^{2+}\): Z = 27 d. Protons in \(_{27}^{59} \mathrm{Co}^{3+}\): Z = 27 e. Protons in \(_{2}^{59} \mathrm{Co}\): Z = 2 (Note: this atom is incorrect, the atomic number should match cobalt's 27) f. Protons in \(_{34}^{79} \mathrm{Se}\): Z = 34 g. Protons in \(_{34}^{79} \mathrm{Se}^{2-}\): Z = 34 h. Protons in \(_{28}^{63} \mathrm{Ni}\): Z = 28 i. Protons in \(_{28}^{59} \mathrm{Ni}^{2+}\): Z = 28

2. Determine Neutrons for Each Atom or Ion#a.

Neutrons are calculated by subtracting the atomic number (Z) from the mass number (A). a. Neutrons in \(_{12}^{24} \mathrm{Mg}\): A - Z = 24 - 12 = 12 b. Neutrons in \(_{12}^{24} \mathrm{Mg}^{2+}\): A - Z = 24 - 12 = 12 c. Neutrons in \(_{27}^{59} \mathrm{Co}^{2+}\): A - Z = 59 - 27 = 32 d. Neutrons in \(_{27}^{59} \mathrm{Co}^{3+}\): A - Z = 59 - 27 = 32 e. Neutrons in \(_{2}^{59} \mathrm{Co}\): A - Z = 59 - 2 = 57 (Note: this atom is incorrect, as the atomic number should match cobalt's 27) f. Neutrons in \(_{34}^{79} \mathrm{Se}\): A - Z = 79 - 34 = 45 g. Neutrons in \(_{34}^{79} \mathrm{Se}^{2-}\): A - Z = 79 - 34 = 45 h. Neutrons in \(_{28}^{63} \mathrm{Ni}\): A - Z = 63 - 28 = 35 i. Neutrons in \(_{28}^{59} \mathrm{Ni}^{2+}\): A - Z = 59 - 28 = 31

3. Determine Electrons for Each Atom or Ion#a.

Electrons equal the number of protons, and when there's a charge, this number will change by the value of the charge. a. Electrons in \(_{12}^{24} \mathrm{Mg}\): Z = 12 b. Electrons in \(_{12}^{24} \mathrm{Mg}^{2+}\): Z - Charge = 12 - 2 = 10 c. Electrons in \(_{27}^{59} \mathrm{Co}^{2+}\): Z - Charge = 27 - 2 = 25 d. Electrons in \(_{27}^{59} \mathrm{Co}^{3+}\): Z - Charge = 27 - 3 = 24 e. Electrons in \(_{2}^{59} \mathrm{Co}\): Z = 2 (Note: this atom is incorrect, as the atomic number should match cobalt's 27) f. Electrons in \(_{34}^{79} \mathrm{Se}\): Z = 34 g. Electrons in \(_{34}^{79} \mathrm{Se}^{2-}\): Z + Charge = 34 + 2 = 36 h. Electrons in \(_{28}^{63} \mathrm{Ni}\): Z = 28 i. Electrons in \(_{28}^{59} \mathrm{Ni}^{2+}\): Z - Charge = 28 - 2 = 26

Key concepts

Protons

Protons are positively charged particles found in the nucleus of an atom. Each element is defined by the number of protons it has, which is known as the atomic number (Z). This number is unique to each element. For example, magnesium (Mg) always has 12 protons, while cobalt (Co) has 27. Protons play a crucial role in the identity of an element, and they remain constant in both neutral atoms and ions. When determining the number of protons, we simply look at the atomic number, without considering whether the species is an atom or ion.

Neutrons

Neutrons are neutral particles that also reside in an atom's nucleus. Unlike protons, neutrons do not have a charge. They serve to add mass to the atom and influence the stability of the nucleus. To find the number of neutrons in an atom or ion, you subtract the atomic number (Z) from the mass number (A), as shown in the formula: \( ext{Neutrons} = A - Z \). The mass number is the total of protons and neutrons in the nucleus. Neutrons can vary in number among atoms of the same element, resulting in isotopes.

Electrons

Electrons are negatively charged particles that orbit the nucleus in various energy levels or shells. In a neutral atom, the number of electrons is equal to the number of protons, balancing the overall charge. For ions, however, this balance changes. Ions are formed when an atom gains or loses electrons:

• Cations are positively charged ions formed by losing electrons.
• Anions are negatively charged ions formed by gaining electrons.

The total count of electrons in an ion is adjusted from the neutral count by the amount of charge it possesses. For example, a \( ext{Mg}^{2+} \) ion has lost two electrons, thus having 10 electrons instead of 12.

Atoms and Ions

Atoms are the basic units of matter, consisting of a nucleus of protons and neutrons, surrounded by electrons. Atoms can exist on their own or combine to form molecules. Ions, on the other hand, are atoms that have gained or lost electrons. This results in a net positive or negative charge.

• Positive ions, or cations, are created when an atom loses one or more electrons.
• Negative ions, or anions, are formed when an atom gains electrons.

The formation of ions is key in chemical reactions, influencing how substances interact, form compounds, and conduct electricity. Understanding the difference between atoms and ions helps us predict and explain the behavior of elements during chemical bonding.