Question

Explain what we mean when we say that a particular element consists of several isotopes.

Short answer

When we say that a particular element consists of several isotopes, we mean that there are different forms of the same element having the same number of protons but varying numbers of neutrons. These isotopes have almost identical chemical properties due to their similar electron configurations, but their different neutron numbers result in varying mass numbers and, consequently, different physical properties. For example, Carbon (C) has three naturally occurring isotopes: ${}^{12}\text{C}$, ${}^{13}\text{C}$, and ${}^{14}\text{C}$, with 6, 7, and 8 neutrons in their nuclei, respectively.

Step-by-step solution

Understanding Elements

Elements are pure substances that cannot be broken down into simpler substances by ordinary chemical means. They are composed of atoms that have the same number of protons in their nucleus, which is represented by the atomic number (Z). However, atoms of an element can have different numbers of neutrons in their nucleus. This variation leads to the existence of isotopes.

Defining Isotopes

Isotopes are atoms of the same element with the same number of protons but different numbers of neutrons in their nuclei. In other words, they have the same atomic number (Z), but different mass numbers (A) due to the variation in the number of neutrons.

Isotopes of an Element

When we say that a particular element consists of several isotopes, we mean that there are different forms of the same element having the same number of protons but varying numbers of neutrons. These isotopes have almost identical chemical properties because their electron configurations are the same. However, the different neutron numbers result in varying mass numbers and, consequently, different physical properties. For example, the element Carbon (C) has three naturally occurring isotopes: Carbon-12 (${}^{12}\text{C}$), Carbon-13 (${}^{13}\text{C}$), and Carbon-14 (${}^{14}\text{C}$). All these isotopes have six protons (as their atomic number is 6) but have 6, 7, and 8 neutrons respectively in their nuclei, resulting in different mass numbers (12, 13, and 14). In summary, when we say that a particular element consists of several isotopes, we refer to the existence of various forms of the same element that have the same number of protons but different numbers of neutrons, leading to distinct mass numbers and physical properties.

Key concepts

Atomic Number

Imagine the atomic number as a unique identifier for each element on the periodic table. Like your social security number is exclusive to you, the atomic number is exclusive to an element. Specifically, it tells us the number of protons found in the nucleus of an atom. Because the atomic number defines the type of element, all atoms with the same atomic number are considered the same element. For example, every atom of hydrogen has an atomic number of 1, meaning each possesses one proton in its nucleus.

No two different elements share the same atomic number, which helps scientists keep the elements organized and identifiable. So, when you're looking at the periodic table, the atomic number is what you'll find at the top of each element's square – it's their elemental 'name tag.'

Mass Number

The mass number of an atom might remind you of someone's total weight; it represents the total number of protons and neutrons in an atom's nucleus. However, unlike weight that can fluctuate, an atom's mass number is constant (unless the atom undergoes nuclear reactions or decay).

The mass number is important because it tells scientists about the 'heaviness' of different atoms. You won't find this number on the periodic table, as it isn't a fixed characteristic of an element due to the presence of isotopes. Speaking of which, let's clarify this by considering our carbon example: Carbon-12 and Carbon-13 are both carbon atoms, but they weigh slightly differently – their mass numbers are 12 and 13, respectively, due to the differing number of neutrons.

Elements and Isotopes

Diving into the diversity of elements, isotopes emerge as the variations of the same element with different wardrobe options, so to speak. The number of protons in their nucleus is their 'essential outfit,' while the number of neutrons is like a changeable 'accessory' that can vary. This means that isotopes of an element have the same atomic number (just like how all shirts might be the same size) but have different mass numbers due to the differing amount of 'accessories' (neutrons).

For instance, picture helium with an atomic number of 2. Both isotopes Helium-3 and Helium-4 share this identity, revealing they comfortably fit into the 'helium category.' Yet they differ in mass; Helium-3 is a bit 'lighter' for having two protons and one neutron, while Helium-4 has a 'heavier feel' due to its two additional neutrons.

Neutron Variation in Isotopes

Every isotope is like a sibling in a large family; similar in many ways but with an individual twist. For isotopes, this twist is the neutron count. As isotopes of an element, they maintain the same number of protons; however, the neutron number can vary, giving each isotope its unique identity in terms of mass.

These variations in neutron counts don't affect an isotope's chemical behavior significantly, which is governed by electrons in most cases. Yet, they can lead to a variety of physical properties and even changes in stability among isotopes. As a result, some isotopes are stable and abundant in nature, while others are unstable, existing for only fleeting moments before transforming into other elements or isotopes.