Isotopes
Isotopes are atoms of the same element that contain different numbers of neutrons. For these species, the number of electrons and protons remain constant. This difference in neutron amount affects the atomic mass (A) but not the atomic number (Z). In a chemical laboratory, isotopes of an element appear and react the same. For this reason, it is difficult to distinguish between an atom's isotopes. In contrast, nuclear scientists can identify and separate different types of atomic nuclei. The technology required for this process is more sophisticated that what could be found in a typical chemical laboratory.
Isotopes are: atoms of the same element that have the same number of neutrons. Atoms of the same element that have different number of protons. Atoms of the same element that have different number of electrons. Atoms of the same element that have different number of neutrons. None of the above. Isotopes are atoms of the same element with different numbers of neutrons. Option a cannot be correct because differences in electron numbers describes ions, not isotopes. Options b, d, and e all.
Scanner utilities for mac. The element carbon ((ce{C})) has an atomic number of 6, which means that all neutral carbon atoms contain 6 protons and 6 electrons. In a typical sample of carbon-containing material, 98.89% of the carbon atoms also contain 6 neutrons, so each has a mass number of 12. An isotope of any element can be uniquely represented as ({}_Z^{A}X) where X is the atomic symbol of the element. The isotope of carbon that has 6 neutrons is therefore (ce{_6^{12}C}) The subscript indicating the atomic number is actually redundant because the atomic symbol already uniquely specifies Z. Consequently, it is more often written as (ce{^{12}C}), which is read as “carbon-12.” Nevertheless, the value of (Z) is commonly included in the notation for nuclear reactions because these reactions involve changes in (Z).
Most elements on the periodic table have at least two stable isotopes. For example, in addition to (ce{^{12}C}), a typical sample of carbon contains 1.11% (ce{_6^{13}C}), with 7 neutrons and 6 protons, and a trace of (ce{_6^{14}C}), with 8 neutrons and 6 protons. The nucleus of (ce{_6^{14}C}) is not stable, however, but undergoes a slow radioactive decay that is the basis of the carbon-14 dating technique used in archeology. Many elements other than carbon have more than one stable isotope; tin, for example, has 10 isotopes. There are about twenty elements that exist in only one isotopic form (sodium and fluorine are examples of these).
An important series of isotopes is found with hydrogen atoms. Most hydrogen atoms have a nucleus with only a single proton. About 1 in 10,000 hydrogen nuclei, however, also has a neutron; this particular isotope is called deuterium. An extremely rare hydrogen isotope, tritium, has 1 proton and 2 neutrons in its nucleus. Figure (PageIndex{1}) compares the three isotopes of hydrogen.
There are currently over 3,500 isotopes known for all the elements. When scientists discuss individual isotopes, they need an efficient way to specify the number of neutrons in any particular nucleus. A/Z and symbol-mass formats can be used to display periodic table information. When viewing either of these two notations, isotopic differences can be obtained.
The discovery of isotopes required a minor change in Dalton’s atomic theory. Dalton thought that all atoms of the same element were exactly the same.
Look at the A/Z formats for the three isotopes of hydrogen in Table (PageIndex{1}). Note how the atomic number (bottom value) remains the same while the atomic masses (top number) are varied. All isotopes of a particular element will vary in neutrons and mass. This variance in mass will be visible in the symbol-mass format of same isotopes as well.
| Common Name | A/Z formats | symbol-mass format | Expanded Name |
|---|---|---|---|
| Hydrogen | (mathrm{^{1}_{1}H}) | (text{H-1}) | hydrogen-1 |
| Deuterium | (mathrm{^{2}_{1}H}) | (text{H-2}) | hydrogen-2 |
| Tritium | (mathrm{^{3}_{1}H}) | (text{H-3}) | hydrogen 3 |
Both A/Z or symbol-mass formats can be utilized to determine the amount of subatomic particles (protons, neutrons, and electrons) contained inside an isotope. When given either format, these mass values should be used to calculate the number of neutrons in the nucleus.
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
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: Amplitube 2 for mac.
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
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.
Isotopes Of All Elements
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 Are Atoms Of The Same Element That Have Different *
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