Problem 68 - Chemistry Matter and Change

Question

Mercury An isotope of mercury has 80 protons and 120 neutrons. What is the mass number of this isotope?

Step-by-Step Solution

Answer

The mass number of the mercury isotope is 200.

Step 1: Understanding the Mass Number

The mass number of an isotope is determined by the sum of its protons and neutrons. Since protons and neutrons are the primary contributors to the mass of an atom, we will use this information to find the mass number.

Step 2: Identifying Protons and Neutrons

For this isotope of mercury, we know there are 80 protons and 120 neutrons.

Step 3: Calculating the Mass Number

To find the mass number, we add the number of protons (80) to the number of neutrons (120):\[Mass\ Number = Number\ of\ Protons + Number\ of\ Neutrons = 80 + 120\]

Step 4: Result of the Calculation

By performing the addition, we find:\[Mass\ Number = 80 + 120 = 200\]Thus, the mass number of this mercury isotope is 200.

Key Concepts

Protons and Neutrons

Protons and neutrons are fundamental particles found in the nucleus of an atom. They are often referred to as nucleons.

• Protons carry a positive charge, while neutrons are neutral, having no charge at all.
• The number of protons in an atom determines the element's chemical identity and is known as the atomic number.
• Neutrons, although uncharged, play a crucial role in providing the nuclear stability, especially in larger atoms.

Together, protons and neutrons account for almost all of the atom's mass. This is why the mass number is the sum of these nucleons. In our example of the mercury isotope, knowing it has 80 protons and 120 neutrons makes it easy to understand how its mass number is calculated.

Isotopes

Isotopes are variants of a particular chemical element that have the same number of protons but a different number of neutrons.

• This means they have different mass numbers due to the variance in neutron count.
• Isotopes maintain the chemical properties of their element because they have the same number of protons.
• However, isotopes can differ in terms of stability, with some being radioactive.

For example, the different isotopes of mercury have the same number of protons (80) but can have different numbers of neutrons. The particular isotope in question contains 120 neutrons, leading to a mass number of 200.

Atomic Structure

Understanding atomic structure is key to grasping basic chemistry concepts. An atom consists of electrons, protons, and neutrons.

• Electrons move in a cloud around the nucleus and are negatively charged.
• The nucleus, at the atom's center, is made up of positively charged protons and neutral neutrons.
• The majority of an atom's mass resides in its nucleus since protons and neutrons are much heavier than electrons.

The atomic structure not only defines the element's identity but also influences how it interacts with other atoms. With atomic number and mass considered together, scientists can predict an atom's behavior. The isotope of mercury discussed here displays how element variations exist within the same atomic structure framework.

Nuclear Composition

Nuclear composition refers to the configuration and quantity of particles within the nucleus of an atom. Understanding this helps in calculating the mass number.

• The nucleus comprises protons and neutrons, which determine not only the element's identity but also its isotope.
• By adding up the protons and neutrons, one can determine the attributable mass number of the atom.
• This sum is crucial as it affects the atomic weight and reflects the stability and radioactivity of the isotopes.

The isotope discussed here has a nuclear composition of 80 protons and 120 neutrons, making it clear why its mass number is 200. The insight into nuclear composition allows for a deeper understanding of the nuanced differences between isotopes of the same element.