Problem 92 - Chemistry The Central Science In Si Units

Question

Identify the element represented by each of the following symbols and give the number of protons and neutrons in each: \((\mathbf{a}){ }_{5}^{11} \mathrm{X}(\mathbf{b}){ }_{33}^{75} \mathrm{X}(\mathbf{c}) \frac{86}{36} \mathrm{X}(\mathbf{d}){ }_{30}^{67} \mathrm{X}\).

Step-by-Step Solution

Answer

(a) Boron: 5 protons, 6 neutrons; (b) Arsenic: 33 protons, 42 neutrons; (c) Krypton: 36 protons, 50 neutrons; (d) Zinc: 30 protons, 37 neutrons.

Step 1: Analyze Element Symbol (a)

The symbol given is \( (a) \ {}^{11}_5 X \). The number at the bottom left, 5, is the atomic number, indicating the number of protons. The atomic number 5 corresponds to the element Boron (B). To find the number of neutrons, subtract the atomic number from the mass number: \( 11 - 5 = 6 \). Therefore, element (a) is Boron with 5 protons and 6 neutrons.

Step 2: Analyze Element Symbol (b)

The symbol given is \( (b) \ {}^{75}_{33} X \). The atomic number is 33, which means it has 33 protons and corresponds to the element Arsenic (As). To find the number of neutrons, subtract the atomic number from the mass number: \( 75 - 33 = 42 \). So element (b) is Arsenic with 33 protons and 42 neutrons.

Step 3: Analyze Element Symbol (c)

The symbol given is \( (c) \ \frac{86}{36} X \). The atomic number at the bottom left is 36, indicating 36 protons, which corresponds to the element Krypton (Kr). The mass number is 86, so the neutrons are calculated as \( 86 - 36 = 50 \). Thus, element (c) is Krypton with 36 protons and 50 neutrons.

Step 4: Analyze Element Symbol (d)

The symbol given is \( (d) \ {}^{67}_{30} X \). With an atomic number of 30, the element is Zinc (Zn), having 30 protons. The neutron count is found by subtracting the atomic number from the mass number: \( 67 - 30 = 37 \). Therefore, element (d) is Zinc with 30 protons and 37 neutrons.

Key Concepts

Atomic Number

The atomic number is a fundamental concept in chemistry and atomic physics. It represents the number of protons found in the nucleus of an atom. This key characteristic not only defines the identity of the element but also helps in determining its place on the periodic table.
For instance, when we say that Boron has an atomic number of 5, we are indicating that every Boron atom contains 5 protons. This is crucial because the atomic number gives us a clear identity of the chemical element.

• The atomic number is symbolized as \( Z \).
• Each element has a unique atomic number.
• The sequence of atomic numbers defines the order of elements in the periodic table.

By understanding atomic numbers, students can easily identify elements based on their position on the periodic table.

Mass Number

Mass number is a vital term that refers to the total number of protons and neutrons in an atom's nucleus. It gives a rough estimate of an atom’s mass, because electrons have negligible mass.
Consider the expression \( ^{11}_5 X \), where 11 is the mass number. This tells us that the atom comprises 11 protons and neutrons combined.

• The mass number is represented typically by the symbol \( A \).
• The mass number is always a whole number.
• It is used to calculate the number of neutrons in an atom by the formula: Neutrons = Mass Number - Atomic Number.

Understanding the mass number allows us to differentiate between various isotopes of the same element, which have identical atomic numbers but different mass numbers.

Protons and Neutrons

Protons and neutrons form the central part of an atom, known as the nucleus, and are thus called nucleons. They are crucial for defining the properties and stability of the atom.
Protons carry a positive charge, while neutrons are neutral, meaning they have no charge. Together, they contribute to the bulk of the atom's mass.

• Protons dictate the chemical behavior and reactivity of an element.
• Neutrons stabilize the atomic nucleus by offsetting the repulsive forces between protons.
• The number of neutrons can vary in atoms of the same element, leading to isotopes.

By knowing the number of protons and neutrons, students can explain various properties such as isotopic variations and understand the stability of elements.