Ca electron configuration - AboutTranscript. Electron configurations describe where electrons are located around the nucleus of an atom. For example, the electron configuration of lithium, 1s²2s¹, tells us that lithium has two electrons in the 1s subshell and one electron in the 2s subshell. Created by Sal Khan.

 
Revision notes on 1.1.5 Electron Configuration for the AQA A Level Chemistry syllabus, written by the Chemistry experts at Save My Exams. ... Calcium has 20 electrons so the full electronic configuration is: 1s 2 2s 2 2p 6 3s 2 3p 6 4s 2. The 4s orbital is lower in energy than the 3d subshell and is therefore filled first;. Buybuybaby store

So that's the electron configuration for silicon. Now, we can write it out using noble gas notation. And compare, so, the noble gas immediately preceding silicon, if we go up a row and then move over, we see that it's neon. So we write neon in brackets. And then, the other electrons are the ones that come after neon. Jul 3, 2019 · Video: Cr, Cr2+, and Cr3+ Electron Configuration Notation. In writing the electron configuration for Chromium the first two electrons will go in the 1s orbital. Since 1s can only hold two electrons the next 2 electrons for Chromium go in the 2s orbital. The next six electrons will go in the 2p orbital. The p orbital can hold up to six electrons.Electron configuration. In atomic physics and quantum chemistry, the electron configuration is the distribution of electrons of an atom or molecule (or other physical structure) in atomic or molecular orbitals. [1] For example, the electron configuration of the neon atom is 1s2 2s2 2p6, meaning that the 1s, 2s, and 2p subshells are occupied by ... How to write calcium electron configuration. The electronic configuration of Ca is 1s2 2s2 2p6 3s2 3p6 4s2 which is written using the following steps-. S orbit can …The gallium atom donates three electrons in the last shell to form a gallium ion (Ga 3+ ). Ga – 3e – → Ga 3+. Here, the electron configuration of gallium ion (Ga 3+) is 1s 2 2s 2 2p 6 3s 2 3p 6 3d 10. Gallium atom exhibits +3 oxidation state. The oxidation state of the element changes depending on the bond formation.The electron configuration shows the distribution of electrons into subshells. This list of electron configurations of elements contains all the elements in increasing order of atomic number.. To save room, the configurations are in noble gas shorthand.This means part of the electron configuration has been replaced with the …Apr 29, 2022 · The full electron configuration of titanium is 1s2 2s2 2p6 3s2 3p6 4s2 3d2 and the abbreviated electron configuration is [Ar]3d24s2. With the Electron configuration of each element, it is possible to specify how the electrons are structured in the atoms of this element. In the case of titanium, its average radius is 140 pm, its covalent radius ...Benefits of Electronic Payment - The main benefit of electronic payment is the convenience it provides to consumers. Learn more about electronic payment at HowStuffWorks. Advertise...How to write calcium electron configuration. The electronic configuration of Ca is 1s2 2s2 2p6 3s2 3p6 4s2 which is written using the following steps-. S orbit can hold maximum 2 electrons. P orbit can hold maximum 6 electrons. D orbit can hold maximum 10 electrons and. F orbit can hold maximum 14 electrons. Each orbital can fill certain number ...Jul 27, 2021 · Write the noble gas configuration by writing the noble gas core, followed by the valence electrons. A noble gas core is the noble gas element symbol enclosed in brackets: [He], [Ne], [Ar], [Kr], [Xe], or [Rn]. The valence electrons are “leftover” electrons that don’t fill a shell or satisfy the octet rule (except for noble gases) or 18 ... In this case, the calcium atom carries a positive charge. Ca – 2e – → Ca 2+. Here, the electron configuration of calcium ion (Ca 2+) is 1s 2 2s 2 2p 6 3s 2 3p 6. This positive calcium ion (Ca 2+) has twenty protons, twenty neutrons, and eighteen electrons. Calcium ion. Electron configuration through orbitals follows different principles. For example Aufbau principle, Hund’s principle, and Pauli’s exclusion principle. Electron configuration of Beryllium through orbit. Scientist Niels Bohr was the first to give an idea of the atom’s orbit. He provided a model of the atom in 1913.The electron configuration for selenium is 1s22s22p63s23p64s23d104p4. This configuration is also written as [Ar] 4s23d104p4, according to Dr. Anne Marie Helmenstine, a contributor ...What she was doing was writing the electron configuration of silicon. Written in full this is 1s2 2s2 2s6 3s2 3p2. However, the first part of this long expression, 1s2 2s2 2s6, is the electron configuration of neon. Therefore, to shorten the configuration for silicon she …In this case, 2+2+6+2+6+2+10+6+2+1= 39 and Z=39, so the answer is correct. A slightly more complicated example is the electron configuration of bismuth (symbolized Bi, with …Calcium, the 20 th element, has two further electrons that go in the fourth shell. In the shorthand notation for electron configuration, the number of electrons in each shell can be written rather than drawn. Each shell is separated by a full stop or a comma. For nitrogen this would be 2.5 or 2,5 and for calcium this would be 2.8.8.2 or 2,8,8,2.Nov 30, 2021 · To write the orbital diagram for the Calcium atom (Ca) first we need to write the electron configuration for just Ca. To do that we need to find the number o... Philips Electronics News: This is the News-site for the company Philips Electronics on Markets Insider Indices Commodities Currencies StocksCa – 2e – → Ca 2+ The electron configuration of calcium ion(Ca 2+) is 1s 2 2s 2 2p 6 3s 2 3p 6. The electron configuration of calcium ion(Ca 2+) shows that calcium ion has three shells and the last shell has eight electrons(3s 2 3p 6). This electron configuration shows that the calcium atom has acquired the electron configuration of argon ... Referring to either Figure 2.6.3 2.6. 3 or 2.6.4 2.6. 4, we would expect to find the electron in the 1 s orbital. By convention, the ms = +1 2 m s = + 1 2 value is usually filled first. The electron configuration and the orbital diagram are: Following hydrogen is the noble gas helium, which has an atomic number of 2. So that's the electron configuration for silicon. Now, we can write it out using noble gas notation. And compare, so, the noble gas immediately preceding silicon, if we go up a row and then move over, we see that it's neon. So we write neon in brackets. And then, the other electrons are the ones that come after neon. The electron configuration for selenium is 1s22s22p63s23p64s23d104p4. This configuration is also written as [Ar] 4s23d104p4, according to Dr. Anne Marie Helmenstine, a contributor ...In this video we will write the electron configuration for Ca2+, the Calcium ion. We’ll also look at why Calcium forms a 2+ ion and how the electron configur...AboutTranscript. Electron configurations describe where electrons are located around the nucleus of an atom. For example, the electron configuration of lithium, 1s²2s¹, tells us that lithium has two electrons in the 1s subshell and one electron in the 2s subshell. Created by Sal Khan. Friedrich Hund. Richard Wilhelm Heinrich Abegg. electronic configuration, the arrangement of electrons in orbitals around an atomic nucleus. The electronic configuration of an atom in the quantum-mechanical model is stated by listing the occupied orbitals, in order of filling, with the number of electrons in each orbital indicated by superscript.Are you planning a getaway to Napa, CA? If so, finding the perfect vacation rental is essential for a memorable and enjoyable trip. Napa is home to several neighborhoods that offer...For example, sodium (Na), which has a single electron in its outer 3s orbital, can lose that electron to attain the electron configuration of neon. Chlorine, with seven valence electrons, can gain one electron to attain the configuration of argon. When two different elements have the same electron configuration, they are called isoelectronic.Similarity of valence shell electron configuration implies that we can determine the electron configuration of an atom solely by its position on the periodic table. ... the UC Davis Library, the California State University Affordable Learning Solutions Program, and Merlot. We also acknowledge previous National Science Foundation support under ...Feign is a declarative web service client. It makes writing web service clients easier. To use Feign, create an interface and annotate it. It has pluggable annotation support inclu...Jan 21, 2021 · What is the Electron Configuration of Calcium. Calcium’s atomic number is 20 which means that in a neutral calcium atom, in its nucleus there are 20 protons. The electron configuration of a Ca ion is 1s^2 2s^2 2p^6 3s^2 3p^6 4s^2. Calcium Electron Configuration (Ca) with Calcium Orbital Diagram and its symbol are present here. Jun 27, 2022 · The valence electron configuration for aluminum is 3s 2 3p 1. So it would have three dots around the symbol for aluminum, two of them paired to represent the 3s electrons: \[\dot{Al:} onumber onumber \] The valence electron configuration for selenium is 4s 2 4p 4. In the highest-numbered shell, the n = 4 shell, there are six electrons. Its ... According to Hund's rule, the sixth electron enters the second of those p orbitals and has the same spin as the fifth electron. 2.7: Electron Configurations is shared under a CC BY-NC-SA 3.0 license and was authored, remixed, and/or curated by LibreTexts. There are a set of general rules that are used to figure out the electron configuration of ...So that's the electron configuration for silicon. Now, we can write it out using noble gas notation. And compare, so, the noble gas immediately preceding silicon, if we go up a row and then move over, we see that it's neon. So we write neon in brackets. And then, the other electrons are the ones that come after neon. That is, magnesium is a cation element. Mg – 2e – → Mg 2+. The electron configuration of magnesium ion (Mg +2) is 1s 2 2s 2 2p 6. This electron configuration shows that magnesium ion (Mg +2) has acquired the electron configuration of neon and it achieves an octave full stable electron configuration. Calcium. (Ca) Calcium is a chemical element of the periodic table with chemical symbol Ca and atomic number 20 with an atomic weight of 40.0784 u and is classed as alkaline earth metal and is part of group 3 (scandium group). Calcium is solid at room temperature. Potassium Periodic table Scandium. The periodic table can be a powerful tool in predicting the electron configuration of an element. However, we do find exceptions to the order of filling of orbitals that are shown in Figure 4.1.3 or Figure 4.1.4.For instance, the electron configurations (shown in Figure 4.1.6) of the transition metals chromium ([latex]\ce{Cr}[/latex]; atomic number 24) and …So, lose two electrons, and when calcium loses two electrons, it becomes the calcium 2-plus cation. And then we can write the electron configuration really short, or it'll be really short because we know it's going to lose these two valence electrons and then, it will have the electron configuration which is just the same as argon.Nov 18, 2013 · A step-by-step description of how to write the electron configuration for Calcium (Ca). In order to write the Ca electron configuration we first need to kno... Aug 11, 2023 · Now the atomic number of calcium (Ca) is 20. Hence the electron arrangement in calcium is 2, 8, 8, 2. And the electron configuration of calcium is 1s 2 2s 2 2p 6 3s 2 3p 6 4s 2. This electron arrangement and electron configuration indicates that the outermost orbit (i.e orbit number 4) of calcium element has 2 electrons. Hence, it lies in group 2. The easiest way to create electron configurations is using an electron configuration table, which is a way of writing down the various orbitals available to electrons. This table is easy to remember, and it makes it possible to generate the electron configuration table for any given element. It looks something like this. See full list on valenceelectrons.com Many Periodic Table chart available on homapage. Ground State Electron Configuration for Calcium While writing the configuration we put all 20 electrons in orbitals around the calcium’s nucleus atom. So …Jun 16, 2016 · The complete electron for a neutral arsenic atom is: "1s"^2"2s"^2"2p"^6"3s"^2"3p"^6"3d"^(10)"4s"^2"4p"^3 Its shorthand electron configuration is: ["Ar"]"3d"^(10)"4s"^2"4p"^3 As is the chemical symbol for the element arsenic. Its atomic number is 33, which is the number of protons in the nuclei of its atoms. In a neutral atom, …Referring to either Figure 2.6.3 2.6. 3 or 2.6.4 2.6. 4, we would expect to find the electron in the 1 s orbital. By convention, the ms = +1 2 m s = + 1 2 value is usually filled first. The electron configuration and the orbital diagram are: Following hydrogen is the noble gas helium, which has an atomic number of 2.Nov 2, 2015 · The electron configuration of a neutral calcium atom is 1s22s22p63s23p64s2. A calcium 2 + ion has lost its two valence electrons, and now has 18 electrons. The electron configuration of a Ca2+ ion is 1s22s22p63s23p6, which is isoelectronic with the noble gas argon. The electron configuration of a "Ca"^ (2+)" ion is "1s"^2"2s"^2"2p"^6"3s"^2"3p"^6".Oct 12, 2020 · In several cases, the ground state electron configurations are different from those predicted by Figure 7.8.1 7.8. 1. Some of these anomalies occur as the 3 d orbitals are filled. For example, the observed ground state electron configuration of chromium is [Ar]4 s1 3 d5 rather than the predicted [Ar]4 s2 3 d4. Jul 3, 2019 · When we write the configuration we'll put all 17 electrons in orbitals around the nucleus of the Chlorine atom. In writing the electron configuration for Chlorine the first two electrons will go in the 1s orbital. Since 1s can only hold two electrons the next 2 electrons for Chlorine go in the 2s orbital. The next six electrons will go in the ...Based on the above rules, The electronic configuration of Calcium is given by. 1s 2 , 2s 2, 2p 6,3s 2,3p 6,4s 2. or. 2, 8,8,2. So it is not like 2,8,10 or 2,8,9,1 as you might think. we can write the electron configuration in the orbital diagram as below. Sometimes, we can write the electron configuration in short form as [Ar] 4s 2Benefits of Electronic Payment - The main benefit of electronic payment is the convenience it provides to consumers. Learn more about electronic payment at HowStuffWorks. Advertise...The gallium atom donates three electrons in the last shell to form a gallium ion (Ga 3+ ). Ga – 3e – → Ga 3+. Here, the electron configuration of gallium ion (Ga 3+) is 1s 2 2s 2 2p 6 3s 2 3p 6 3d 10. Gallium atom exhibits +3 oxidation state. The oxidation state of the element changes depending on the bond formation.Electronic banking takes several forms. Using a debit card, visiting an automated teller machine and banking by cellphone are all types of electronic banking. If you set up an onli...Jul 17, 2023 ... I understand the explanation of 4s2 being ionized first because 3d becomes lower in energy after 2 electrons. But shouldn't Ca be [Ar]3d2, ...So that's the electron configuration for silicon. Now, we can write it out using noble gas notation. And compare, so, the noble gas immediately preceding silicon, if we go up a row and then move over, we see that it's neon. So we write neon in brackets. And then, the other electrons are the ones that come after neon. OK, here we go: (Part 1:) A single (isolated) Mg or Ca atom in its electronic ground state is diamagnetic, as you would predict from its ground-state electron configuration of (1s)2(2s)2(2p)6(3s)2. (Part 2:) However, a chunk of Mg or Ca metal contains a lot of Mg (or Ca) atoms. You haven't yet learnt about how the atomic orbitals (AOs) on one ...The electron configuration and the orbital diagram are: Following hydrogen is the noble gas helium, which has an atomic number of 2. The helium atom contains two protons and two electrons. The first electron has the same four quantum numbers as the hydrogen atom electron ( n = 1, l = 0, ml = 0, ms = +½). 4.6 Electronic configuration (ESABE) The energy of electrons (ESABF). The electrons of an atom all have the same charge and the same mass, but each electron has a different amount of energy.Electrons that have the lowest energy are found closest to the nucleus (where the attractive force of the positively charged nucleus is the greatest) and the …Revision notes on 1.1.5 Electron Configuration for the AQA A Level Chemistry syllabus, written by the Chemistry experts at Save My Exams. ... Calcium has 20 electrons so the full electronic configuration is: 1s 2 2s 2 2p 6 3s 2 3p 6 4s 2. The 4s orbital is lower in energy than the 3d subshell and is therefore filled first;This electron configuration calculator will instantly show you the distribution of electrons in the orbitals of any periodic element you choose. Typically, you need at …Friedrich Hund. Richard Wilhelm Heinrich Abegg. electronic configuration, the arrangement of electrons in orbitals around an atomic nucleus. The electronic configuration of an atom in the quantum-mechanical model is stated by listing the occupied orbitals, in order of filling, with the number of electrons in each orbital indicated by superscript.So now let's think about what the electron configuration of the scandium would be. Pause this video and think about that. Well scandium has one more proton than calcium. It …Dec 3, 2020 ... Receive Comprehensive Mathematics Practice Papers Weekly for FREE Click this link to get: ▶️▶️▶️ https://iitutor.com/email-list/ ...The electron configuration and the orbital diagram are: Following hydrogen is the noble gas helium, which has an atomic number of 2. The helium atom contains two protons and two electrons. The first electron has the same four quantum numbers as the hydrogen atom electron ( n = 1, l = 0, ml = 0, ms = +½).That is, magnesium is a cation element. Mg – 2e – → Mg 2+. The electron configuration of magnesium ion (Mg +2) is 1s 2 2s 2 2p 6. This electron configuration shows that magnesium ion (Mg +2) has acquired the electron configuration of neon and it achieves an octave full stable electron configuration. If we lose two electrons, we have a net deposited two charge. We form the calcium to ion. The two electrons that we would lose to form the calcium two plus ion are these. These two electrons right here in the 4s orbital. The electron configuration for calcium two plus would be the same as the electron configuration for the noble gas argon here. Jan 15, 2024 · According to Hund's rule, the sixth electron enters the second of those p orbitals and has the same spin as the fifth electron. 2.8: Electron Configurations is shared under a CC BY-NC-SA 3.0 license and was authored, remixed, and/or curated by LibreTexts. There are a set of general rules that are used to figure out the electron configuration of ... Jul 3, 2019 · When we write the configuration we'll put all 17 electrons in orbitals around the nucleus of the Chlorine atom. In writing the electron configuration for Chlorine the first two electrons will go in the 1s orbital. Since 1s can only hold two electrons the next 2 electrons for Chlorine go in the 2s orbital. The next six electrons will go in the ...We expect that its electron configuration should end with s 2. Calcium’s electron configuration is [Ar]4s 2. Sn is located in the second column of the p block, so we expect that its electron configuration would end in p 2. …Calcium's electron configuration, which was first determined in Exercise 2.6.1, is shown below. 1 s 2 2 s 2 2 p 6 3 s 2 3 p 6 4 s 2 Calcium has 2 valence electrons, as determined either by totaling the electrons found within the orbitals in the highest occupied energy level, which, in this case, is the 4 s orbital, or by identifying the "A/B ... The periodic table can be a powerful tool in predicting the electron configuration of an element. However, we do find exceptions to the order of filling of orbitals that are shown in Figure 4.1.3 or Figure 4.1.4.For instance, the electron configurations (shown in Figure 4.1.6) of the transition metals chromium ([latex]\ce{Cr}[/latex]; atomic number 24) and copper …RetroPie is our favorite image for turning your Raspberry Pi into a retro video game station, and today it gets a bunch of great features. RetroPie is our favorite image for turnin...Friedrich Hund. Richard Wilhelm Heinrich Abegg. electronic configuration, the arrangement of electrons in orbitals around an atomic nucleus. The electronic configuration of an atom in the quantum-mechanical model is stated by listing the occupied orbitals, in order of filling, with the number of electrons in each orbital indicated by superscript.Jul 3, 2019 · How to Write the Electron Configuration for Beryllium. Beryllium is the fourth element with a total of 4 electrons. In writing the electron configuration for beryllium the first two electrons will go in the 1s orbital. Since 1s can only hold two electrons the remaining 2 electrons for Be go in the 2s orbital.Calcium's symbol is “Ca” and atomic number is “20.” Free calcium hardly exists in nature, as it is highly reactive. Calcium is produced usually in supernova ...Jan 18, 2024 · Let us return to the electron configuration of nitrogen and write it again: Find the atomic number of nitrogen (7) and use this electron configuration calculator to get a complete electron configuration. Otherwise, write the order of the energy levels with electron configuration chart: 1 s 2 2 s 2 2 p 3 \rm 1s^22s^22p^3 1 s 2 2 s 2 2 p 3. Feb 1, 2014 · The total electron configuration is: 1s22s22p63s23p64s2 or [Kr]4s2. The valence electrons are found in the highest energy level of the electron configuration in the 's' and 'p' orbitals. In the case of calcium this is 4s2. This gives calcium an 's' orbital with a pair of electrons in its valence shell. I hope this was helpful. The electron configurations of a few elements are provided with illustrations in this subsection. Electron Configuration of Hydrogen. The atomic number of hydrogen is 1. Therefore, a hydrogen atom contains 1 electron, which will be placed in the s subshell of the first shell/orbit. The electron configuration of hydrogen is 1s 1, as illustrated ... The shorthand electron configuration for Calcium is [Ar] 4s 2. The electron configuration for Calcium ion (Ca 2+) is 1s 2 2s 2 2p 6 3s 2 3p 6. The number of valence electrons available for the Calcium atom is 2. Calcium is situated in Group 2nd and has an atomic number of 20.Referring to either Figure 2.6.3 2.6. 3 or 2.6.4 2.6. 4, we would expect to find the electron in the 1 s orbital. By convention, the ms = +1 2 m s = + 1 2 value is usually filled first. The electron configuration and the orbital diagram are: Following hydrogen is the noble gas helium, which has an atomic number of 2. Here's your inside look at JSX's new E145s with a 1-1 seating configuration. Editor’s note: JSX provided behind-the-scenes access and a complimentary flight to TPG. The opinions ex...

The periodic table can be a powerful tool in predicting the electron configuration of an element. However, we do find exceptions to the order of filling of orbitals that are shown in Figure 4.1.3 or Figure 4.1.4.For instance, the electron configurations (shown in Figure 4.1.6) of the transition metals chromium ([latex]\ce{Cr}[/latex]; atomic number 24) and …. White ferrari

ca electron configuration

Are you having trouble activating CTV.ca on your device? Don’t worry, you’re not alone. Many users experience issues when trying to activate their CTV.ca account, but with a little...Jul 27, 2018 · Abbreviated ground state electron configuration: [Ne]3s23p5. Answer link. full ground state electron configuration: 1s^2 2s^2 2p^6 3s^2 3p^5 abbreviated: " [Ne]" 3s^2 3p^5 Chlorine has an atomic number of 17, which means it has 17 protons and therefore 17 electrons in its atomic form. We'll need to know how many sublevel is present in each ...The electronic configuration for Ca is 1 s 2 2 s 2 2 p 6 3 s 2 3 p 6 4 s 2. The calcium atom loses two electrons for the formation of Ca 2 +. So, two electrons are removed from the 4s orbital for the formation of Ca 2 +. Hence, the electronic configuration of Ca 2 + is 1 s 2 2 s 2 2 p 6 3 s 2 3 p 6. Suggest Corrections. 10. Similar questions.The Order of Filling Orbitals. The aufbau principle explains how electrons fill low energy orbitals (closer to the nucleus) before they fill higher energy ones. Where there is a choice between orbitals of equal energy, they fill the orbitals singly as far as possible (Hunds rules).The diagram (not to scale) summarizes the energies of the orbitals up to the 4p level.Mar 23, 2023The total electron configuration is: 1s22s22p63s23p64s2 or [Kr]4s2. The valence electrons are found in the highest energy level of the electron configuration in the 's' and 'p' orbitals. In the case of calcium this is 4s2. This gives calcium an 's' orbital with a pair of electrons in its valence shell. I hope this was helpful.2 days ago · Hund’s Rule. However, one can write the electronic configuration just by understanding the Aufbau principle. It states that, in the ground state, the electrons occupy the atomic orbitals in their order of increasing energies, which is given by n+l rule. Higher the value of n+l for the orbital, higher is the energy.A p orbital in the fourth shell and we have one electron so we can write 4p1. And so this is one way to represent the electron configuration for gallium using noble gas notation. So argon 4s2 3d10 4p1. Sometimes you might see the 3d10 and the 4s switched in terms of their orders. You might see 3d10, 4s2, 4p1. Jul 27, 2018 · Abbreviated ground state electron configuration: [Ne]3s23p5. Answer link. full ground state electron configuration: 1s^2 2s^2 2p^6 3s^2 3p^5 abbreviated: " [Ne]" 3s^2 3p^5 Chlorine has an atomic number of 17, which means it has 17 protons and therefore 17 electrons in its atomic form. We'll need to know how many sublevel is present in each ...The complete electron configuration of calcium is 1s2 2s2 2p6 3s2 3p6 4s2. Calcium have 2 valence electrons around the nucleus and the atomic number is 20. The distribution of electrons are as 2 electrons in 1s subshell, 2 electrons in 2s subshell, 6 electrons in 2p subshell, 2 electrons in 3s subshell , 6 electrons in 3p subshell and remaining ... May 15, 2020 · What’s the electron configuration of a Ca 2 ion Weegy? A calcium 2+ ion has lost its two valence electrons, and now has 18 electrons. The electron configuration of a Ca2+ ion is 1s22s22p63s23p6 , which is isoelectronic with the noble gas argon. What is the electronic configuration of calcium Class 9? The number of electrons for the Ca atom is 20.A review of Virgin Atlantic's leisure configured Airbus A350 aircraft from Manchester to Orlando featuring 'The Booth' social space. How many business class seats should an airline....

Popular Topics