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Course: High school chemistry > Unit 1
Lesson 2: Isotopes and ionsIsotopes
Isotopes are atoms of the same element with different numbers of neutrons. Since isotopes of an element have different numbers of neutrons, they also have different masses. The sum of the number of neutrons and protons in an atom is called its mass number. Isotopes can be represented in writing using isotope notation. Created by Khan Academy.
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Do all elements have isotopes?(12 votes)
Yes, all elements have isotopes! But some are exceedingly rare.(26 votes)
- If an isotope is an atom with a different number of neutrons then electrons, how is carbon 12 an isotope if it has 6 protons and 6 neutrons?(4 votes)
Carbon-12 is an isotope because it is one of the possible forms of carbon atoms. An isotope is defined by the number of protons and neutrons in its nucleus, not by the number of electrons. Carbon atoms have 6 protons, but they can have different numbers of neutrons, such as 6, 7, or 8. These are called carbon-12, carbon-13, and carbon-14, respectively. They are all isotopes of carbon, but they have different masses and properties. Carbon-12 is the most abundant and stable isotope of carbon, accounting for 98.9% of element carbon on Earth(12 votes)
- why do isotopes exist?? what is the reason for different numbers of neutrons(3 votes)
That's a great question. Isotopes exist because of the very way elements are created. These are natural processes that involve primarily (but aren't limited to) nuclear reactions. You have probably heard people like Neal deGrasse Tyson, Brian Cox or Brian Greene talk about stars and nebulae, and how they are stellar nurseries.
Let's take Carbon as an example: in the core of stars (like our sun), there's this process called nuclear fusion, in which the pressure is so ridiculously great, hydrogen nuclei (protons) are forced to combine and form helium nuclei. As the temperature and pressure increase, helium nuclei can then fuse to form carbon nuclei (I am making this simple to get the message across, but you can google "triple-alpha process" for more information). Three helium nuclei then combine to form a carbon-12 nucleus. Here we have our first isotope. During this process, some of the carbon-12 nuclei can capture additional neutrons to form carbon-13. This whole process involding nuclear reactions to create carbon istopes is called stellar nucleosynthesis (again, you can google it for more info).
Carbon-14, on the other hand, is formed in the Earth's atmosphere. Out there in the universe, there are high-energy cosmic rays originating from sources even outside our solar system. These cosmic rays collide with nitrogen-14 nuclei found in our atmosphere, and this results in the production of carbon-14. This process is ongoing and maintains a constant level of carbon-14 in the atmosphere.
Because of that, the relative abundance of isotopes can vary. Carbon-12 is the most abundant isotope of carbon, accounting for about 98.9% of natural carbon. Carbon-13 makes up about 1.1% of natural carbon, and carbon-14 is present in trace amounts, but it is still detectable and useful for various applications, such as radiocarbon dating.
So, again, to answer your question, isotopes (like carbon-12, carbon-13, and carbon-14) are formed through processes such as stellar nucleosynthesis in stars and interactions between cosmic rays and atmospheric nuclei. These processes lead to variations in the number of neutrons in the carbon nuclei, resulting in different isotopes of the element, and therefore in different properties also (such as their rates of radioactive decay).(12 votes)
- To find a mass number we need to know the number of protons right?But we don't know the # of protons.How should we find # of protons.(2 votes)
the atomic number is the # of protons(12 votes)
- at1:42where did the second 6 come from?(2 votes)
she is telling the number of protons in carbon
hope you understood her meaning and found that she was talking about protons in carbon(2 votes)
- What is the rarest isotope?(2 votes)
- Tantalum (Ta-180)(2 votes)
- Do elements have many atoms?(2 votes)
It depends greatly. If you get a very small amount of the element, then it will obviously have rather few atoms. But if you get a larger amount of the element, then there will be more atoms.(1 vote)
- Why does proton define the chemiscal element? why could not be the neutron or eletron?(2 votes)
- The proton is crucial in defining chemical elements because it determines the identity of an atom. An atom's identity is determined by the number of protons in its nucleus, which is called the atomic number. For example, all atoms with one proton in their nucleus are hydrogen atoms, those with two protons are helium atoms, and so forth. This unique number of protons distinguishes one element from another in the periodic table.
While both neutrons and electrons are important components of an atom, they do not define the element itself. Neutrons contribute to the mass of the atom and help stabilize the nucleus, but they do not affect the atom's chemical properties. Electrons are involved in chemical reactions and bonding, but their number can vary within an element's atoms without changing its identity.
In summary, the proton defines the chemical element because it determines the atomic number, which is the fundamental characteristic that distinguishes one element from another.
hope it helped(1 vote)
1:42Video transcript
- [Instructor] Every element is defined by the number of protons in its atoms, which is called its atomic number. So for example, every atom
of potassium has 19 protons and every atom of cobalt has 27 protons. But what about neutrons? Well, an element doesn't
always have the same number of neutrons in its atoms. Atoms of the same element with
different numbers of neutrons are called isotopes. Because isotopes of an element have different numbers of neutrons, those isotopes also have different masses. Remember, most of the mass of an atom comes from the protons and
neutrons in its nucleus. In fact, the sum of the number of protons and neutrons in an atom
is called its mass number. We can write this in the form
of an equation as follows, mass number equals the number of protons, plus the number of neutrons. Next, let's dive into isotope notation, or how we represent isotopes in writing. When describing different isotopes, you'll often see this notation where X is the chemical symbol, which is an abbreviation
of the element's name, A is the mass number, the
number of protons plus neutrons, and Z is the atomic number,
the number of protons. Let's practice writing out the notation for different isotopes. We'll start with carbon, which has an atomic number of 6. In nature, carbon is mainly composed of two different isotopes. One of these isotopes has 6 neutrons and the other isotope has 7 neutrons. Let's start with the isotope that has 6 protons and 6 neutrons. With that information, we know that the mass number must be 12, which is the sum of the
protons and neutrons. So the notation for this isotope of carbon would look like this. We have the chemical symbol C with the mass number 12
written at its top-left, and the atomic number 6
written at its bottom-left. But for the isotope with
6 protons and 7 neutrons, the mass number would be 6 plus 7, or 13. So the notation for the carbon
isotope would be as follows. Here, we have the chemical symbol C with the mass number 13
written at its top-left, and the atomic number 6
written at its bottom-left. Notice that the chemical
symbol and atomic number share the same information,
the identity of the element, and are the same for both isotopes, but the mass number is
different for each isotope depending on the number of neutrons. Another notation that is used for isotopes is the chemical symbol
or the element's name, symbolized by X, followed by a hyphen, and the mass number,
symbolized by A, so X-A. Let's return to our
carbon isotopes example. For the carbon isotope that
has 6 protons and 6 neutrons, we write that as C-12 or carbon-12. For the carbon isotope with
6 protons and 7 neutrons, we write that as C-13 or carbon-13. Let's wrap up this video
with a quick recap. We know that elements are defined by the number of protons in their atoms, but atoms of the same element can have different numbers of neutrons. These are called isotopes. Because isotopes have
different numbers of neutrons, they also have different mass numbers, which are the sum of
the protons and neutrons in each isotope's atom. An atom's mass number can be
described by the equation, mass number equals the number of protons, plus the number of neutrons. And lastly, we can describe isotopes using a couple of different notations, which are shown below.