Log in JeremyBalec 3 months agoPosted 3 months ago. Direct link to JeremyBalec's post “Why is the periodic table...” Why is the periodic table of elements broken into two parts? • (5 votes) B L Ø Ø ᑐ | Я ᕮ ᑐ | Γ Λ L L 2 months agoPosted 2 months ago. Direct link to B L Ø Ø ᑐ | Я ᕮ ᑐ | Γ Λ L L's post “Anyone who is saying ther...” Anyone who is saying there is no reason is wrong, there is always a reason for everything in science. Here are the reasons (took me half an hour to finish writing this, I hope you enjoy it :) ): (13 votes) William Crye 2 months agoPosted 2 months ago. Direct link to William Crye's post “so If I have a potassium ...” so If I have a potassium (K) and add a proton, it is no longer a potassium, it's a calcium (Ca) right? • (6 votes) FreeRadical 2 months agoPosted 2 months ago. Direct link to FreeRadical's post “Yes, if you add a proton ...” Yes, if you add a proton to potassium you get calcium. (7 votes) Ilearnmath 4 months agoPosted 4 months ago. Direct link to Ilearnmath's post “How did each element get ...” How did each element get their name? Like who came up with the names? • (4 votes) PinklePrin 3 months agoPosted 3 months ago. Direct link to PinklePrin's post “Currently the Internation...” Currently the International Union of Pure and Applied Chemistry (IUPAC) decides elements' names. A lot of elements are named after famous scientists, places, planets, or mythological figures. Other times, their names are associated with their properties or even other elements. Hope this helps! :) (6 votes) ayesha.tanzeem 2 months agoPosted 2 months ago. Direct link to ayesha.tanzeem's post “How come protons neutrons...” How come protons neutrons and electrons aren't the smallest particles on earth, since they're INSIDE the atom? • (3 votes) Limbo 2 months agoPosted 2 months ago. Direct link to Limbo's post “They aren't the smallest ...” They aren't the smallest because they are made of quarks, which are the new smallest thing since atoms (6 votes) laura_gabbard 2 months agoPosted 2 months ago. Direct link to laura_gabbard's post “How did each element get ...” How did each element get their name? Like who came up with the names? • (2 votes) FreeRadical 2 months agoPosted 2 months ago. Direct link to FreeRadical's post “The names of the elements...” The names of the elements are usually given by the people who discovered them. Or the places where they were found. Others have names based on mythology, and still others for their appearance. (6 votes) AdelEye a month agoPosted a month ago. Direct link to AdelEye's post “Wait so if I'm getting th...” Wait so if I'm getting this right, elements are atoms? So they're basically different names for the same things? Or are they different? • (3 votes) TDJ a month agoPosted a month ago. Direct link to TDJ's post “An element is a pure subs...” An element is a pure substance made entirely of one type of atom. (3 votes) laura_gabbard a month agoPosted a month ago. Direct link to laura_gabbard's post “Why is the periodic table...” Why is the periodic table of elements broken into two parts? • (2 votes) Zayan 19 days agoPosted 19 days ago. Direct link to Zayan's post “For practicality. The lan...” For practicality. The lanthanides (the top row of the bottom block) usually fits between barium (56) and hafnium (72). The actinides are normally right below the lanthanides, between radium (88) and rutherfordium (104). These two groups are separated from the main body to save space, because the normal way make the table extremely long (14 extra boxes wide). (5 votes) GraceM 2 months agoPosted 2 months ago. Direct link to GraceM's post “is gold and crystals are ...” is gold and crystals are made of current atoms? • (3 votes) Limbo a month agoPosted a month ago. Direct link to Limbo's post “Yup, gold is an element a...” Yup, gold is an element and crystals are made of various elements depending on what kind of crystal it is. (3 votes) Dragonmaster 3 months agoPosted 3 months ago. Direct link to Dragonmaster's post “What is Og and when was i...” What is Og and when was it discovered? • (2 votes) Good ol' David 2 months agoPosted 2 months ago. Direct link to Good ol' David's post “According to google Og = ...” According to google Og = Oganesson and it was discovered in 2002. It wasn't named Oganesson at he time it used to be called Ununoctium. (4 votes) Volcannon1752 13 days agoPosted 13 days ago. Direct link to Volcannon1752's post “Why is the periodic table...” Why is the periodic table organized how it is? Why is there a large gap at the top? • (3 votes) TheReal3A 6 days agoPosted 6 days ago. Direct link to TheReal3A's post “(Simplifcation)It has to...” (Simplifcation) The gaps on period The even larger hydrogen-helium gap though? The rightmost group is reserved for the noble gases - elements with a completely filled valence shell. Helium has I hope this helps? (3 votes)Want to join the conversation?
The second part of the periodic table contains 2 parts, the Lanthanide series and the Actinide series. There are 3 main reasons why scientists have taken this series out of the main body of the periodic table.
For starters, you have to understand first what electron shells and atomic orbitals are. These are ways scientist have been able to roughly predict the placement of different energy level electrons around the atomic core, in the form of orbits (If you've already taken AP Chem then skip this part). Though more precisely speaking this is just a calculated estimate of the most likely placement for the same level electrons as the form of possibility clouds by using the Schrodinger equation, an orbit is much easier to understand, so we'll go with that. There are 7 lines (excluding the two series outside the table) of the periodic table as you might have noticed, and there is a big chunk missing from the middle of the top. There are also 7 electron shells, KLMNOPQ, and 7 atomic orbitals, spdfghi. In fact, each line of the periodic table matches up with a corresponding electron shell, for example, the first line containing only Hydrogen and Helium contains elements that only have electrons in the K shell; The second line contains 8 elements, from Lithium to Neon, which all only have electrons in the K and L shell; The third line is KLM, the fourth KMLN, the fifth KLMNO and so on. As for atomic orbitals, they are sort of the shell in shell, which means that they are a new division in the electron shell, since electrons of the same shell don't all have the same energy, but they are also not distinct from each other. To categorize them, Bohr used atomic orbitals, which divides different energy electrons in the same shell into different orbitals. the nth shell contains n number of orbitals, and the orbitals with the same symbol but in different shells is differed by a number before them, which is n, the bigger the number, the higher the energy. This means that K only contains the 1s orbital, L contains 2s and 2p, M contains 3s 3p and 3d, N contains 4s 4p 4d and 4f etc.. There are always the same maximum number of electrons in orbitals with the same symbol, even if they are from different shells, s always maxes out at 2, p at 6, d at 10, f at 14 etc., each increasing by 4. Following the Lowest Energy Principle, electrons will always go into the lower energy atomic orbitals first. The energy of the same shell orbitals increase as the symbols increase, s<p<d<f<g<h<i, and the higher n is for the same symbol, the more energy the orbital contains. Now it is easy to treat the first few orbitals, you just put electrons in as the orbitals and shells increase, 2 for 1s, 2 for 2s, 6 for 2p, 2 for 3s, 6 for 3p. But as we reach the last orbital of the M shell, things change. We now face the choice of putting the electron into 4s or 3d. You might think that 4s being in the N shell it will have higher energy, but the fact is, 3d is the d orbital, which itself contains more energy than the s orbital. The fact is from here on we apply the Aufbau principle, which basically tells AP Chem students to memorize the following: after 3p it is: 4s - 3d - 4p - 5s - 4d - 5p - 6s - 4f - 5d - 6p... Here is a link for a detailed description of the Aufbau principle visually from wikipedia: https://en.wikipedia.org/wiki/Aufbau_principle#/media/File:Aufbau_Principle-en.svg
So now it might be dawning on you, as the lines of the periodic table increase, we are getting more and more atoms since the number of electrons in each shell increases, thus we have more atoms to deal with. This is why there is a big chunk missing, cuz the upper few lines only have that many elements. But there is the opposite problem for the 6th and 7th line: They contain more than 18 elements. This is the First reason why the Actinide and Lanthanide series are written separately from the main body part, to make the whole table look much clearer than if they wrote everything out as one.
The second reason has to do with the valence electron shell. The valence electron shell is the part of the electron shell that is responsible for giving the atom its most common ionic charge, or more simply speaking, it is the most outer electron shell of the atom. According to which atomic orbital these electrons are in, chemists assigned names to different parts of the periodic table, with each part containing elements of the same valence orbital type. The IA group to the IIA group are known as the s block, with ns as the valence orbitals; the IIIB group to the VIII group are known as the d block, with (n-1)d^(1-9)ns as the valence orbitals; the IB group to the IIB group are known as the ds block, with (n-1)d^(10)ns as the valence orbitals; the IIIA group to the 0th group are known as the p block, with nsnd^(1-6) as the valence orbitals, the only exception being Helium, which has no p orbitals. Now the Actinide and Lanthanide series are in and are the only elements in the f block, which means their valence orbitals are (n-2)f(n-1)dns. This is the reason why chemists decided to isolate this particular set of elements, and not any other set.
The third reason is because the elements in the Lanthanide and Actinide series have special characteristics that no other set of or lone element(s) have. (Note that these elements have similar characteristics as well, and that in mines of any of these elements, all or many of the elements of the same series stick to each other in the mine, making it hard to separate them.) For example, the Lanthanide series has a famous characteristic called the Lanthanide contraction phenomenon. It states that although the elements in the series like any of the other periods have decreasing atomic radii as the atomic number increases, the rate of decrease in the Lanthanide series is much slower than any other periods. It is the same thing with the Actinide series, the phenomenon is known as Actinide contraction. Other patterns in both include the three plus cations in the series' ionic color change in a pattern of "colorless -> colored -> colorless", and that most of the elements in both series tend to be a good source of electromagnetic material.
Alright, I'm done, I hope this helps :D
It has to do with the capacity of each electron shell.
The row of an element on the periodic table is known as the 'period'. The period tells us the number of electron shells that are occupied.
The column of an element on the periodic table is known as the 'group'. The group tells us the number of valence electrons (electrons on the outermost shell).
Going up the elements, protons increase by 1 and electrons also increase by 1.
- Shell 1 can only hold a maximum of 2 electrons.
- Shell 2 can hold up to 8 electrons.
- The third shell can hold 8 electrons initially. In period 4, shell 4 gains 2 electrons before further filling shell 3 to up to 18 electrons in the period 4 transition metals.
So most transition metals have 2 valence electrons.2 and 3 are formed this way to accommodate for the transition metals.2 electrons, completely filling shell 1.
Video transcript
- [Instructor] We know thateverything in the universe is composed of atoms, but not all atoms are the same. There are many different typesof atoms called elements, each with a unique set ofphysical and chemical properties. Many elements areprobably familiar to you. Oxygen and carbon, forexample, are elements, and so is gold. Others may be less familiar such as bismuth, xenon, and osmium. A particular element is identified by the number of protons in its atoms. And the number of protonsin the nucleus of an atom is its atomic number,represented by the symbol Z. For example, helium hasan atomic number of two. That means that everyhelium atom has two protons. And here's another example, iron, its atomic number is 26, so every iron atom has 26 protons. An element's atomicnumber can also tell us the number of electrons in aneutral atom of an element. Remember, equal and oppositecharges cancel each other out so to be neutral, an atom must have anequal number of protons, which have a charge of 1+, and electrons, which have a charge of 1-. This means that our heliumatom must have two electrons and our iron atom must have 26 electrons. All of the known elements are organized accordingto their atomic numbers in the periodic table. The periodic table lists the elements in order of increasing atomic number as you go from left to rightand from top to bottom. The elements are furtherorganized into columns based on their properties. Elements in the same column tend to have similar physicaland chemical properties. Every element is representedby a chemical symbol, a unique one or two letter abbreviation that appears below theelement's atomic number on the periodic table. Many chemical symbols are based on the Englishname for an element. For example, the symbol for hydrogen is H, and the symbol for aluminum is Al. But some chemical symbols are based on the Latinname for the element. For example, the symbol for lead is Pb, which actually comes fromits Latin name plumbum. Notice that whenever the chemical symbol for an element has two letters, the second letter is written in lowercase. All of this information is contained inside of each element'sbox on the periodic table. For example, here's the boxfor the element nitrogen. At the top of the box is nitrogen's atomicnumber, which is seven. Remember that this is equal to the number of protonsin each atom of nitrogen as well as the number of electrons. Below that is nitrogen'schemical symbol, N, followed by its name. Often, you'll also see another number listed at the bottom of an elements box, which has to do with atomic mass. We'll cover details aboutthis and another video. What's neat about having all of this information in one place is that if we know onedetail about an element, either it's atomic number,chemical symbol, or a name, we can often use the periodic table to find out the other details. Let's take a look at a few examples. Say we have the element phosphorus, what is its atomic numberand chemical symbol? Looking through the periodic table, we can find phosphorus and see that its atomic number is 15 and its chemical symbol is P. Let's do another example. Say we know the chemical symbol Hg, what is this element's name and how many protons does it have? Here is the symbol Hgon the periodic table. Its name is mercury, and its atomic number is 80 so it has 80 protons. Let's reveal. The universe is made up of different types ofatoms called elements, and these elements areorganized by atomic number in the periodic table. So, the next time that youstare up at the starry sky, you know that everything outthere is made up of elements.
