- Identify the atomic number (\(Z\)) as the number of protons: \(Z = 19\).
- Calculate the mass number (\(A\)) as the sum of protons and neutrons: \(A = 19 + 20 = 39\).
- Use the standard isotope notation \({}_{Z}^{A}X\) to represent the element as \({}_{19}^{39} K\).
- The final answer for the mass number and the isotope notation is \(\boxed{{}_{19}^{39} K}\).
Explanation
- Identify the element and its atomic number
The provided information states that the element has 19 protons (\(p^+\)), 19 electrons (\(e^-\)), and 20 neutrons (\(n^0\)). The identity of an element is determined by the number of protons in its nucleus, which is the atomic number (\(Z\)). Since there are 19 protons, the atomic number is \(Z = 19\). Looking at the periodic table, the element with atomic number 19 is Potassium, represented by the symbol \(K\).
- Calculate the mass number
The mass number (\(A\)) of an atom is defined as the sum of the number of protons and the number of neutrons in its nucleus. Using the given values, we calculate the mass number as:
\[A = \text{number of protons} + \text{number of neutrons} = 19 + 20 = 39\]
Thus, the mass number for this specific isotope of potassium is 39.
- Determine the isotope notation
The isotope notation is conventionally written in the form \({}_{Z}^{A}X\), where \(X\) is the chemical symbol, \(A\) is the mass number, and \(Z\) is the atomic number. Having identified \(X = K\), \(A = 39\), and \(Z = 19\), the isotope notation is \({}_{19}^{39} K\). Comparing this to the target format \({ }_{19}^{[?]} K\), the value that replaces the placeholder is 39.
- Final Answer
The mass number of the given element is 39, and the complete isotope notation is \(\boxed{{}_{19}^{39} K}\).
Examples
Isotope notation is essential in fields like medicine and geology. For instance, doctors use radioactive isotopes, such as Technetium-99m, for medical imaging to diagnose diseases. By knowing the mass number (\(A\)) and atomic number (\(Z\)), scientists can track how these isotopes decay and behave, which allows for safe and precise treatments in healthcare settings. Understanding these notations helps you grasp how different forms of the same element interact with the world around us.