Problem 24 - Chemistry: The Central Science in SI Units, Global Edition

Question

Consider an atom of \({ }^{58} \mathrm{Ni}\). (a) How many protons, neutrons, and electrons does this atom contain? (b) What is the symbol of the ion obtained by removing two electrons from \({ }^{58} \mathrm{Ni}\) ? (c) What is the symbol for the isotope of \({ }^{58} \mathrm{Ni}\) that possesses 33 neutrons?

Step-by-Step Solution

Answer

(a) The \({ }^{58}\mathrm{Ni}\) atom contains 28 protons, 30 neutrons, and 28 electrons. (b) The symbol of the ion obtained by removing two electrons from \({ }^{58}\mathrm{Ni}\) is \(\mathrm{Ni}^{2+}\). (c) The symbol for the isotope of \({ }^{58}\mathrm{Ni}\) that possesses 33 neutrons is \({ }^{61}\mathrm{Ni}\).

Step 1: (a) Determine atomic number and mass number

Find the atomic number (Z) and the mass number (A) for Nickel (Ni) atom. We are given the mass number, which is denoted as the superscript in the given atom \({ }^{58}\mathrm{Ni}\). The atomic number (number of protons) can be found by looking at the periodic table.

Step 2: (a) Look up Nickel on the periodic table

Identify the element Nickel (Ni) on the periodic table. Its atomic number (Z) is 28.

Step 3: (a) Calculate the number of protons, neutrons, and electrons

Using the atomic number and mass number, we can determine the number of protons, neutrons, and electrons in the Nickel atom. - The number of protons is equal to the atomic number (Z) which is 28. - The number of neutrons can be calculated as the mass number (A) minus the atomic number (Z): \(58 - 28 = 30\). - In a neutral atom, the number of electrons equals the number of protons, so the number of electrons is also 28.

Step 4: (b) Determine the ion obtained after removing two electrons

When two electrons are removed from the atom, it becomes positively charged as the number of protons (28) remains the same but the number of electrons becomes 28-2=26. The charge of this ion will be +2, as two electrons have been removed. So the symbol for the ion is: \(\mathrm{Ni}^{2+}\).

Step 5: (c) Determine the isotope with 33 neutrons

To find the symbol of the isotope with 33 neutrons, we use the previously determined atomic number (Z=28) and the given number of neutrons (N=33) to find the mass number of this isotope. The mass number (A) can be calculated as the sum of the atomic number (Z) and the number of neutrons (N): \(28 + 33 = 61\). The symbol for this isotope is: \({ }^{61}\mathrm{Ni}\).

Key Concepts

Isotopes

Isotopes are various forms of the same element that differ in the number of neutrons they have. All isotopes of an element have the same number of protons but different numbers of neutrons, resulting in different mass numbers. This difference in mass does not significantly affect the chemical properties, but rather the isotopic mass.

• Isotopes are denoted by a notation that includes the element's symbol, the atomic number, and the mass number. For example, \(^{58}\mathrm{Ni}\) and \(^{61}\mathrm{Ni}\) are isotopes of Nickel.
• The atomic number (protons) remains constant for a given element, while the mass number changes due to the different neutron count.

Understanding isotopes is crucial in fields such as climate science and archaeology, where they are used for dating materials like ice cores and fossils. They also play a role in nuclear medicine and energy.

Periodic Table

The periodic table organizes all known elements systematically, based mainly on their atomic numbers. The atomic number indicates the number of protons found in the nucleus of an atom and determines an element's identity.

• Elements are arranged in order of increasing atomic number from left to right and top to bottom across the table.
• The table is divided into periods (horizontal rows) and groups (vertical columns) that share similar chemical properties.
• Understanding the position of elements on the periodic table helps predict their behavior and gain insights into electron configurations.

Nickel (Ni), for example, is located in the middle of the table, in group 10 and period 4. Its atomic number of 28 indicates 28 protons. The periodic table assists in determining the electron arrangement, where Nickel has an electron configuration of \([Ar] 3d^8 4s^2\). This configuration is essential when evaluating Nickel's chemical reactivity and forming compounds.

Ions

Ions are atoms or molecules that have gained or lost one or more electrons, giving them a net electrical charge. They form when an atom's electron balance is disturbed either by losing or gaining electrons.

• Cations are positively charged ions formed by losing electrons, resulting in more protons than electrons.
• Anions are negatively charged ions formed by gaining electrons, giving more electrons than protons.
• The charge of an ion can be determined by subtracting the number of electrons from the number of protons.

In our example, removing two electrons from \(^{58}\mathrm{Ni}\) results in a cation with a charge of +2, represented as \(\mathrm{Ni}^{2+}\). Because the number of protons remains constant, this shift in balance results in an electrically charged ion. Understanding ions is essential in fields like chemistry and biochemistry as they explain how substances interact, dissolve, and conduct electricity.