Because first electron affinities are typically negative, the elements with a higher electron affinity will have more negative values. Electron affinity decreases down a group because the electrons are placed in higher energy levels in higher valence shells. This decreases the attraction of the nucleus on valence electrons via shielding. Less energy is released by the addition of an electron to caesium. This is because as caesium is larger, it has greater shielding, and a decreased pull of the nucleus on valence electrons.
Across a period from left to right in the periodic table, the electron affinity increases. This is because from left to right in a period, while shielding remains constant, the number of protons in the nucleus increases, increasing the nuclear charge and the influence of the nucleus on the outer electrons.
Ions of Elements. Nuclear Charge of Atoms. Ionisation Energies. Electronegativity of the Elements. Nathan's subject matter ranges from general chemistry and organic chemistry.
Nathan also created the curriculum on Breaking Atom in the course page. Corpuscularism was a theory proposed by Descartes that all matter was composed of tiny particles. Rene Descartes was a famous mathematician and philosopher of the 16th century who hypothesised the theory of corpuscularism about the atom. Semi conductors is a term to describe metalloids that are able to conduct a current when electrical energy is applied due to the movement of electrons but the conductivity measurements are not as high as metals due to fewer electrons to carry a charge or a less ordered structure.
An ionic compound is a bond that forms between metals and non metals to form a large ionic lattice. Nuclear fusion is a process which occurs in. Hydrogen atoms under a lot of heat and pressure are forced together to make a larger atom of helium. Where by if the exact position of the electron is known the momentum will be uncertain.
Werner Heisenberg was a German physicist who was a pioneer in the field of quantum mechanics. He devised the principle of uncertainty relating to the momentum and position of an electron. Lobes refers to the shape of electron waves and the area of highest probability of where that electron as a particle would be found. The Pauli Exclusion refers to the theory that each electron can only have a unique set of the 4 quantum numbers and no two electrons can have the same quantum numbers.
Quantum numbers is a term used to describe the assigning of numbers to electrons as a mathematical function to describe their momentum and energy. The term quantum mechanics refers to energy levels and the theoretical area of physics and chemistry where mathematics is used to explain the behaviour of subatomic particles. Vibrational modes is a term used to describe the constant motion in a molecule. Usually these are vibrations, rotations and translations.
Erwin Schrodinger was an Austrian physicist who used mathematical models to enhance the Bohr model of the electron and created an equation to predicted the likelihood of finding an electron in a given position.
The alkali metals, found in group 1 of the periodic table formally known as group IA , are so reactive that they are generally found in nature combined with other elements. The alkali metals are shiny, soft, highly reactive metals at standard temperature and pressure. Alkaline earth metals is the second most reactive group of elements in the periodic table. They are found in group 2 of the periodic table formally known as group IIA. Unknown elements or transactinides are the heaviest elements of the periodic table.
These are meitnerium Mt, atomic number , darmstadtium Ds, atomic number , roentgenium Rg, atomic number , nihonium Nh, atomic number , moscovium Mc, atomic number , livermorium Lv, atomic number and tennessine Ts, atomic number The post-transition metals are the ones found between the transition metals to the left and the metalloids to the right. Oganesson Og is a radioactive element that has the atomic number in the periodic table, its appearance is not fully known due to the minuscule amounts produced of it.
It is in Group It has the symbol Og. Tennessine Ts is a radioactive element that has the atomic number in the periodic table, its appearance is not fully known due to the minuscule amounts produced of it. It has the symbol Ts. Livermorium Lv is a radioactive element that has the atomic number in the periodic table, its appearance is not fully known due to the minuscule amounts produced of it.
It has the symbol Lv. Moscovium Mc is a radioactive metal that has the atomic number in the periodic table, its appearance is not fully known due to the minuscule amounts produced of it. It has the symbol Mc. Flerovium Fl is a radioactive metal that has the atomic number in the periodic table, its appearance is not fully known due to the minuscule amounts produced of it. It has the symbol Fl. Nihonium Nh is a radioactive metal that has the atomic number in the periodic table, its appearance is not fully known due to the minuscule amounts produced of it.
It has the symbol Nh. Copernicium Cr is a radioactive metal that has the atomic number in the periodic table, its appearance is not fully known due to the minuscule amounts produced of it.
It is a Transition metal in Group It has the symbol Rg. Roentgenium Rg is a radioactive metal that has the atomic number in the periodic table, its appearance is not fully known due to the minuscule amounts produced of it. Darmstadtium Ds is a radioactive metal that has the atomic number in the periodic table, its appearance is not fully known due to the minuscule amounts produced of it.
It has the symbol Ds. Meitnerium Mt is a radioactive metal that has the atomic number in the periodic table, its appearance is not fully known due to the minuscule amounts produced of it.
It is a Transition metal in Group 9. It has the symbol Mt. Hassium Hs is a radioactive metal that has the atomic number in the periodic table, its appearance is not fully known due to the minuscule amounts produced of it. It is a Transition metal in Group 8. It has the symbol Hs.
Bohrium Bh is a radioactive metal that has the atomic number in the periodic table, its appearance is not fully known due to the minuscule amounts produced of it. It is a Transition metal in Group 7. It has the symbol Bh. Seaborgium Sg is a radioactive metal that has the atomic number in the periodic table, its appearance is not fully known due to the minuscule amounts produced of it.
It is a Transition metal in Group 6. It has the symbol Sg. Dubnium Db is a radioactive metal that has the atomic number in the periodic table, its appearance is not fully known due to the minuscule amounts produced of it.
It is a Transition metal in Group 5. It has the symbol Db. Rutherfordium Rf is a radioactive metal that has the atomic number in the periodic table, its appearance is not fully known due to the minuscule amounts produced of it. It is a Transition metal in Group 4. It has the symbol Rf. Lawrencium Lr is a silvery-white colored radioactive metal that has the atomic number in the periodic table.
It is an Actinoid Metal with the symbol Lr. Nobelium No is a radioactive metal that has the atomic number in the periodic table, its appearance is not fully known due to the minuscule amounts produced of it. It is an Actinoid Metal with the symbol No. Mendelevium Md is a radioactive metal that has the atomic number in the periodic table, its appearance is not fully known due to the minuscule amounts produced of it. It is an Actinoid Metal with the symbol Md. Fermium Fm is a silvery-white colored radioactive metal that has the atomic number in the periodic table.
It is an Actinoid Metal with the symbol Fm. Einsteinium Es is a silvery-white colored radioactive metal that has the atomic number 99 in the periodic table. It is an Actinoid Metal with the symbol Es.
Californium Cf is a silvery-white colored radioactive metal that has the atomic number 98 in the periodic table. It is an Actinoid Metal with the symbol Cf. Berkelium Bk is a silvery colored radioactive metal that has the atomic number 97 in the periodic table. It is an Actinoid Metal with the symbol Bk.
Curium Cm is a silvery-white colored radioactive metal that has the atomic number 96 in the periodic table. It is an Actinoid Metal with the symbol Cm. Americium Am is a silvery colored radioactive metal that has the atomic number 95 in the periodic table. It is an Actinoid Metal with the symbol Am.
Plutonium Pu is a silvery colored radioactive metal that has the atomic number 94 in the periodic table. It is an Actinoid Metal with the symbol Pu. Neptunium Np is a silvery colored radioactive metal that has the atomic number 93 in the periodic table. It is an Actinoid Metal with the symbol Np.
Protactinium Pa is a shiny silver colored radioactive metal that has the atomic number 91 in the periodic table. It is an Actinoid Metal with the symbol Pa. Thorium Th is a silvery-white colored radioactive metal that has the atomic number 90 in the periodic table. It is an Actinoid Metal with the symbol Th. Actinium Ac is a silvery colored radioactive metal that has the atomic number 89 in the periodic table. It is an Actinoid Metal with the symbol Ac. Radium Ra is a silvery-white colored metal that has the atomic number 88 in the periodic table.
It is an Alkaline earth Metal with the symbol Ra and is located in Group 2 of the periodic table. Francium Fr is thought to be a gray colored metal that has the atomic number 87 in the periodic table. It is an Alkali Metal with the symbol Fr and is located in Group 1 of the periodic table. Radon Rn is a colourless, odourless, radioactive gas non-metal that has the atomic number 86 in the periodic table in Group It has the symbol Rn.
Astatine At is a radioactive non-metal that has the atomic number 85 in the periodic table in Group It has the symbol At. Polonium Po is a silvery-gray metal that has the atomic number 84 in the periodic table in Group It has the symbol Po.
Bismuth Bi is a hard steel-gray metal that has the atomic number 83 in the periodic table in Group It has the symbol Bi. Lead Pb is a soft gray metal that has the atomic number 82 in the periodic table in Group Periodic Properties.
Search for:. Electron Affinity. Learning Objective Recognize the general periodic trends for electron affinity. Key Points The electron affinity of an atom or molecule is the propensity for that particle to gain an electron. This is an exothermic process for all non-noble gas elements. There are general trends in electron affinity across and down the periodic table of elements.
Electron affinity generally increases across a period in the periodic table and sometimes decreases down a group. These trends are not necessarily universal. The chemical rationale for changes in electron affinity across the periodic table is the increased effective nuclear charge across a period and up a group. Show Sources Boundless vets and curates high-quality, openly licensed content from around the Internet.
Licenses and Attributions. However, comparing chlorine and bromine, say, makes things seem more difficult because of the more complicated electronic structures involved. What we have said so far is perfectly true and applies to the fluorine-chlorine case as much as to anything else in the group, but there's another factor which operates as well which we haven't considered yet - and that over-rides the effect of distance in the case of fluorine.
The incoming electron is going to be closer to the nucleus in fluorine than in any other of these elements, so you would expect a high value of electron affinity.
However, because fluorine is such a small atom, you are putting the new electron into a region of space already crowded with electrons and there is a significant amount of repulsion. This repulsion lessens the attraction the incoming electron feels and so lessens the electron affinity.
A similar reversal of the expected trend happens between oxygen and sulphur in Group 6. The first electron affinity of oxygen kJ mol -1 is smaller than that of sulphur kJ mol -1 for exactly the same reason that fluorine's is smaller than chlorine's. As you might have noticed, the first electron affinity of oxygen kJ mol -1 is less than that of fluorine kJ mol Similarly sulphur's kJ mol -1 is less than chlorine's kJ mol It's simply that the Group 6 element has 1 less proton in the nucleus than its next door neighbour in Group 7.
The amount of screening is the same in both. That means that the net pull from the nucleus is less in Group 6 than in Group 7, and so the electron affinities are less. The reactivity of the elements in group 7 falls as you go down the group - fluorine is the most reactive and iodine the least. Often in their reactions these elements form their negative ions.
At GCSE the impression is sometimes given that the fall in reactivity is because the incoming electron is held less strongly as you go down the group and so the negative ion is less likely to form. That explanation looks reasonable until you include fluorine!
An overall reaction will be made up of lots of different steps all involving energy changes, and you cannot safely try to explain a trend in terms of just one of those steps. Fluorine is much more reactive than chlorine despite the lower electron affinity because the energy released in other steps in its reactions more than makes up for the lower amount of energy released as electron affinity.
You are only ever likely to meet this with respect to the group 6 elements oxygen and sulphur which both form 2- ions. The second electron affinity is the energy required to add an electron to each ion in 1 mole of gaseous 1- ions to produce 1 mole of gaseous 2- ions. The positive sign shows that you have to put in energy to perform this change.
The second electron affinity of oxygen is particularly high because the electron is being forced into a small, very electron-dense space.
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