Problem 55 - Chemistry An Atoms First Approach

Question

Identify each of the following elements. Give the number of protons and neutrons in each nucleus. a. \({ }_{15}^{31} \mathrm{X}\) b. \({ }_{53}^{127} \mathrm{X}\) c. \({ }_{19}^{39} \mathrm{X}\) d. \({ }_{70}^{173} \mathrm{X}\)

Step-by-Step Solution

Answer

a. Phosphorus (P) with 15 protons and 16 neutrons. b. Iodine (I) with 53 protons and 74 neutrons. c. Potassium (K) with 19 protons and 20 neutrons. d. Ytterbium (Yb) with 70 protons and 103 neutrons.

Step 1: Element a: \({ }_{15}^{31} \mathrm{X}\)

The atomic number Z = 15, so we look for the element with 15 protons, which is Phosphorus (P). The mass number A = 31, so we have 31 nucleons in total (protons + neutrons). Since we already know there are 15 protons, we can calculate the number of neutrons as follows: Number of neutrons = A - Z = 31 - 15 = 16 Element a is Phosphorus with 15 protons and 16 neutrons.

Step 2: Element b: \({ }_{53}^{127} \mathrm{X}\)

The atomic number Z = 53, so we look for the element with 53 protons, which is Iodine (I). The mass number A = 127, so we have 127 nucleons in total (protons + neutrons). Since we already know there are 53 protons, we can calculate the number of neutrons as follows: Number of neutrons = A - Z = 127 - 53 = 74 Element b is Iodine with 53 protons and 74 neutrons.

Step 3: Element c: \({ }_{19}^{39} \mathrm{X}\)

The atomic number Z = 19, so we look for the element with 19 protons, which is Potassium (K). The mass number A = 39, so we have 39 nucleons in total (protons + neutrons). Since we already know there are 19 protons, we can calculate the number of neutrons as follows: Number of neutrons = A - Z = 39 - 19 = 20 Element c is Potassium with 19 protons and 20 neutrons.

Step 4: Element d: \({ }_{70}^{173} \mathrm{X}\)

The atomic number Z = 70, so we look for the element with 70 protons, which is Ytterbium (Yb). The mass number A = 173, so we have 173 nucleons in total (protons + neutrons). Since we already know there are 70 protons, we can calculate the number of neutrons as follows: Number of neutrons = A - Z = 173 - 70 = 103 Element d is Ytterbium with 70 protons and 103 neutrons.

Key Concepts

Atomic Number

The atomic number, often represented as

Mass Number

When you hear the term 'mass number', it is referring to the total count

Protons and Neutrons

Exploring deeper into the nucleus of an atom, we encounter two of

Element Identification

One of the fundamental skills in understanding chemistry is the ability