Isotopes are variants of a particular chemical element which differ in neutron number, and consequently in nucleon number. All isotopes of a given element have the same number of protons but different numbers of neutrons in each atom. Question: Isotopes are atoms of the same element with different numbers of neutrons the same element with different numbers of protons different elements with the same number of neutrons the same element with the same masses Strong forces between nucleons are forces of attraction holding the particles together o are independent of the charges of the particles are. Isotopes are variants of a particular chemical element which differ in neutron number, and consequently in nucleon number. All isotopes of a given element have the same number of protons but different numbers of neutrons in each atom.
- Isotopes Are Atoms Of The Same Element With Different Numbers Of Blank And Therefore Different Blank
- Isotopes Are Atoms Of The Same Element With Different Numbers Of Which Results In Different Numbers
- Isotopes Of An Atom Differ In Their
- Isotopes Of All Elements
GENERAL CHEMISTRY TOPICS
Isotopes
An isotope is made up of atoms of the same element that have the same atomic mass. Different isotopes of an element arise from atoms with differing numbers of neutrons. Uses of isotopes. Average atomic masses from natural abundances: The weighted-average calculation.
Atomic number, mass number and isotopes
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The atomic number of an element (symbolized as Z) is the number of protons in the nuclei of its atoms. The mass number (A) is the total number of nucleons (neutrons and protons). An isotope is made up of atoms of the same element (which by definition have a characteristic and fixed atomic number) that also have the same mass number. Different isotopes of an element arise from atoms with differing numbers of neutrons. Because of this, chemists need a way to represent specific isotopes of an element. Isotopes of an element have the same atomic number, but different mass numbers. The atomic number, when represented along with the symbol of an element, is shown as a leading subscript. The mass number is shown as a leading superscript. Since the element symbol implies an atomic number, the latter is often dropped, and an isotope as commonly represented textually with just the mass number and the element symbol (for example 14C or 18O).
In the periodic table, the elements, represented as their symbols, are arranged in a particular pattern that reflects (as we will see) a regularity, or periodicity in their properties. Typically in the table, the element symbol is contained within its own small box, along with other information including the atomic number and the average atomic mass. The average atomic mass of an element represents the averages of its naturally occurring isotopic masses weighted according to their natural abundance. The formula for calculation of average atomic mass and illustration of its use is presented below.
How do the isotopic forms of an element differ from one another, physically and chemically? Isotopes are defined by their subatomic particle composition, which we will think of as a physical property. The chemistry of an element is determined by, in a general sense, the number of valence electrons its atoms possess. The number of valence electrons associated with a neutral atom is in turn determined by the number protons in the nucleus. Thus, two atomic nuclei could have the same number of protons, but different numbers of neutrons. Yet since the atoms they are part of would still have the same number of valence electrons, these two atoms would be chemically indistinguishable.*
Uses of isotopes
There are a wide variety of applications of isotopes in nuclear chemistry, medicine, biochemistry, anthropology, paleontology, and geology. Many such uses are based on the phenomenon of radioactivity, shown by some of the isotopes of many of the elements. Such radioactive isotopes are unstable, undergoing spontaneous nuclear decay processes at a rate determined by the half-life of the isotope. One example is the use of 14C - the isotope of carbon with six protons and eight neutrons, which has a half-life of 5730 years - as a basis for dating of materials derived from living organisms that are many thousands of years old. This technique, called radiocarbon dating, is used widely in geosciences and anthropology.
Average atomic masses from natural abundances: The weighted-average calculation
The atomic masses given in the periodic table represent weighted averages based on the natural abundances of the isotopes of a given element. The formula for a weighted average is
Here the xi's are the masses of the individual isotopes, and the wi's are the fractional abundances corresponding to the isotopes. Note that the weights must sum to 1 (equivalently the percent abundances must sum to 100%).
For example, chlorine exists in two isotopic forms, 35Cl and 37Cl. The mass of the 35Cl isotope is 34.97 amu and that of 37Cl is 36.97 amu. The abundances are 75.77% and 24.23%, repectively. Therefore in this case, the weighted average becomes
wa = (0.7577)(34.97 amu) + (0.2423)(36.97 amu) = 35.45 amu
The result of this calculation is the atomic mass of chlorine that appears in the periodic table.
* Actually, since isotopes of an element differ in atomic mass, they can be subtly distinguished by differences in reaction rates, or in physical processes - such as rate of diffusion - affected by mass.
Isotopes Are Atoms Of The Same Element With Different Numbers Of Blank And Therefore Different Blank
Atoms are the smallest particle of an element that retains the characteristics of the element.
For Example: The gold nugget in the diagram is made up of individual gold atoms.
Gold Atom Diagram
The circle represents the nucleus of a gold atom. Outside the nucleus of the gold atom are 79 electrons (negative charges). Electrons move around the nucleus.
Inside the nucleus of the gold atom are 79 protons (positive charges).Only carbon atoms have 79 protons.
I repeat:ONLY GOLD ATOMS have 79 protons.
Atomic Number:
Every element has a different atomic number. The atomic number of an element is the number of protons that each atom of that element has. The atomic number of Gold is 79.
Every gold atom has 79 protons. Only gold atoms have 79 protons.
Each gold atom has 79 protons in its nucleus. Have you noticed that the number of protons for a gold atom is equal to the number of electrons that a gold atom has?
FACT: An atom has an equal number of protons and electrons. All gold atoms have the same number of protons and electrons. But all gold atoms are not exactly alike.
Mass Number
The mass number of an atom is the sum of the protons and neutrons in the nucleus of the atom.
Neutron: A particle found inside the nucleus of an atom. This particle does not have a charge.
The Mass Number for the gold atom in the diagram is 79 P + 118 N = 197
Isotopes Are Atoms Of The Same Element With Different Numbers Of Which Results In Different Numbers
Isotopes
Isotopes: Atoms of the same element that have different atomic masses.
Isotopes: Atoms of the same element that have the same number of protons, but a different number of neutrons.
Isotopes can be identified by writing their name or symbol and their mass number. For example:
Gold-197 or Au-197. This is the only natural isotope of gold. The mass number of this isotope is given after the elements name. The diagram for Au-197 contains 79 protons and 118 neutrons
Isotopes Of An Atom Differ In Their
Challenge:
1. What is the name of the gold isotope shown in the diagram to the left?
Answer:
Think!
1. You know it is a gold isotope because it has 79 protons.
2. The mass number of any atom is equal to the number of protons plus the number of neutrons in the atom’s nucleus.
3. The mass number for the diagram is: 79 protons + 119 neutrons = 198
4. The name of a specific isotope of an element is the:
elements name + mass number (gold-198)
symbol of the element + mass number (Au-198)
Isotopes Of All Elements
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