The quest to identify an element based on its electronic and nuclear composition is a fundamental aspect of chemistry and physics. Understanding the structure of atoms, including the number of electrons, protons, and neutrons, is crucial for determining an element's properties and its position in the periodic table. In this context, we are tasked with finding an element that has exactly 19 electrons and 21 neutrons.
Atomic Structure Basics
To solve this, let’s first recall some basics of atomic structure. The number of electrons in a neutral atom equals the number of protons, which defines the element’s atomic number (Z). The total number of neutrons and protons in an atom’s nucleus gives us the mass number (A). The atomic number (number of protons) determines the element, while the mass number (protons + neutrons) can vary among isotopes of the same element.
Identifying the Element with 19 Electrons
An atom with 19 electrons has an atomic number of 19. According to the periodic table, the element with atomic number 19 is Potassium (K). Potassium is an alkali metal with various applications, including in fertilizers and as a critical component in certain types of glass.
Isotopes and Neutron Count
Now, let’s consider the neutron count. The most abundant isotope of Potassium has a mass number of 39 (19 protons and 20 neutrons). However, we are looking for an isotope with exactly 21 neutrons. To find the mass number of this specific isotope, we add the number of protons (19) to the number of neutrons (21), which gives us a mass number of 40.
Potassium-40: The Isotope with 19 Electrons and 21 Neutrons
The isotope of Potassium with a mass number of 40, denoted as Potassium-40 or 40K, has 19 protons, 21 neutrons, and 19 electrons in its neutral state. This isotope is one of the three naturally occurring isotopes of Potassium, alongside 39K and 41K. 40K is radioactive, undergoing beta decay with a half-life of approximately 1.25 billion years.
| Isotope | Protons | Neutrons | Electrons |
|---|---|---|---|
| 39K | 19 | 20 | 19 |
| 40 | 19 | 21 | 19 |
| 41K | 19 | 22 | 19 |
Key Points
- The element with 19 electrons is Potassium (K), which has an atomic number of 19.
- The isotope of Potassium with exactly 21 neutrons is 40K.
- 40K has 19 protons, 21 neutrons, and 19 electrons.
- This isotope is radioactive with a half-life of about 1.25 billion years.
- Potassium has several naturally occurring isotopes, including 39K, 40K, and 41K.
The identification of 40K as the isotope with 19 electrons and 21 neutrons illustrates the nuanced understanding required to navigate the complexities of atomic structure and isotopic variations. This knowledge is foundational to fields such as nuclear physics, chemistry, and geology.
What element has 19 electrons?
+The element with 19 electrons is Potassium (K). In its neutral state, Potassium has 19 protons, 19 electrons, and typically 20 neutrons in its most abundant isotope.
Which isotope of Potassium has 21 neutrons?
+The isotope of Potassium with 21 neutrons is 40K. This isotope has 19 protons and 21 neutrons, giving it a mass number of 40.
Is 40K stable?
+No, 40K is not stable. It is radioactive, undergoing beta decay with a half-life of approximately 1.25 billion years.