Unstable isotopes decay through various radioactive decay pathways, most commonly alpha decay, beta decay, or electron capture. Many other rare types of decay, such as spontaneous fission or neutron emission are known. It should be noted that all of these decay pathways may be accompanied by the subsequent emission of gamma radiation.
Pure alpha or beta decays are very rare. The periodic table is a tabular display of the chemical elements organized on the basis of their atomic numbers, electron configurations, and chemical properties. The electron configuration is the distribution of electrons of an atom or molecule or other physical structure in atomic or molecular orbitals.
Knowledge of the electron configuration of different atoms is useful in understanding the structure of the periodic table of elements. Every solid, liquid, gas, and plasma is composed of neutral or ionized atoms. The chemical properties of the atom are determined by the number of protons, in fact, by number and arrangement of electrons.
It is the Pauli exclusion principle that requires the electrons in an atom to occupy different energy levels instead of them all condensing in the ground state. This fact has key implications for the building up of the periodic table of elements. The first two columns on the left side of the periodic table are where the s subshells are being occupied. Because of this, the first two rows of the periodic table are labeled the s block.
Similarly, the p block are the right-most six columns of the periodic table, the d block is the middle 10 columns of the periodic table, while the f block is the column section that is normally depicted as detached from the main body of the periodic table. It could be part of the main body, but then the periodic table would be rather long and cumbersome.
For atoms with many electrons, this notation can become lengthy and so an abbreviated notation is used. The electron configuration can be visualized as the core electrons, equivalent to the noble gas of the preceding period, and the valence electrons e. Oxidation states are typically represented by integers which may be positive, zero, or negative. Most elements have more than one possible oxidation state.
It also has a pretty low density and under standard conditions, it is the least dense solid element. Lithium is the lightest of all metals and is named from the Greek work for stone lithos. It is the first member of the Alkali Metal family. It is less dense than water with which it reacts and forms a black oxide in contact with air. Being on the upper left side of the Periodic Table, lithium has a fairly low electronegativity and electron affinity as compared to the rest of the elements.
Also, lithium has high metallic character and subsequently lower nonmetallic character when compared with the other elements. Lithium has a higher atomic radius than most of the elements on the Periodic Table. In its pure form it is soft and silvery white and has a relatively low melting point oC. Lithium is part of the Group 1 Alkali Metals , which are highly reactive and are never found in their pure form in nature.
This is due to their electron configuration, in that they have a single valence electron Figure 1 which is very easily given up in order to create bonds and form compounds. When placed in contact with water, pure lithium reacts to form lithium hydroxide and hydrogen gas.
Out of all the group 1 metals, lithium reacts the least violently, slowly releasing the hydrogen gas which may create a bright orange flame only if a substantial amount of lithium is used. This occurs because lithium has the highest activation energy of its group - that is, it takes more energy to remove lithium's one valence electron than with other group 1 elements, because lithium's electron is closer to its nucleus.
Atoms with higher activation energies will react slower, although lithium will release more total heat through the entire process. These compounds give the normally the silver-white metal a black tarnish. Additionally, it will combust with oxygen as a red flame to form lithium oxide. Lithium is able to be used in the function of a Lithium battery in which the Lithium metal serves as the anode. Most questions answered within 4 hours.
Choose an expert and meet online. No packages or subscriptions, pay only for the time you need. Chemistry Mcat Teas. As a result, when he performed his measurements, he was actually observing the averaged properties of all the different isotopes in the sample. For most of our purposes in chemistry, we will do the same thing and deal with the average mass of the atoms.
Luckily, aside from having different masses, most other properties of different isotopes are similar. There are two main ways in which scientists frequently show the mass number of an atom they are interested in. It is important to note that the mass number is not given on the periodic table.
These two ways include writing a nuclear symbol or by giving the name of the element with the mass number written. To write a nuclear symbol , the mass number is placed at the upper left superscript of the chemical symbol and the atomic number is placed at the lower left subscript of the symbol.
The complete nuclear symbol for helium-4 is drawn below:. The following nuclear symbols are for a nickel nucleus with 31 neutrons and a uranium nucleus with neutrons.
In the nickel nucleus represented above, the atomic number 28 indicates that the nucleus contains 28 protons, and therefore, it must contain 31 neutrons in order to have a mass number of The uranium nucleus has 92 protons, as all uranium nuclei do; and this particular uranium nucleus has neutrons.
Another way of representing isotopes is by adding a hyphen and the mass number to the chemical name or symbol. Thus the two nuclei would be Nickel or Ni and Uranium or U, where 59 and are the mass numbers of the two atoms, respectively. Note that the mass numbers not the number of neutrons are given to the side of the name. This page was constructed from content via the following contributor s and edited topically or extensively by the LibreTexts development team to meet platform style, presentation, and quality:.
Learning Objectives Explain what isotopes are and how an isotope affects an element's atomic mass.
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