is wo2 ionic or covalent
There are five lone pairs of electrons in the molecule of SO. There is/are _3_ hydrogen atom/s present in this chemical formula NH3. Thus, the compound formed from sodium and chlorine will be ionic (a metal and a non-metal). As it is such an important molecule, we need to study its molecular structure and bonding behavior. The formation of ionic bonds corresponds to the distinct electronegativities of participating atoms so that atoms with higher electronegativity are strong enough to attract the valence electrons of atoms with lower electronegativity. To add one thing to the discussion on molecular geometries, a single, unpaired electron counts just like a lone pair of electrons (at a first approximation). In 5e D&D and Grim Hollow, how does the Specter transformation affect a human PC in regards to the 'undead' characteristics and spells? Write the molecular formula for each compound. Binary molecular ( covalent) compounds are formed as the result of a reaction between two nonmetals. Even if each B-F bond is polar, the net dipole moment iszerobecause adding the bond vectors cancels everything out.Check the full article hereIs BF3 polar or nonpolar?. Any compound made up of non-metals will form a covalent bond, while compounds made of a metal and non-metal form an ionic bond. The name of a simple covalent compound can be determined from its chemical formula. Because sodium is a metal and we recognize the formula for the phosphate ion, we know that this compound is ionic. So according to me, it should be ionic. To produce a strong covalent bond, both the participating atoms need to have high ionization energy which is the case of the oxygen atom. Furthermore, whereas ionic compounds are good conductors of electricity when dissolved in water, most covalent compounds, being electrically neutral, are poor conductors of electricity in any state. Silicon dioxide is formed when isolated silicon is exposed to an abundant amount of oxygen. Connect and share knowledge within a single location that is structured and easy to search. The sharing means that the bond will be considered covalent/molecular.---Helpful ResourcesMetals, Non-Metals on the P- Table: https://youtu.be/OoooStZQHdAIonic, Covalent, \u0026 Polar Covalent: https://youtu.be/OHFGXfWB_r4Electronegativity for each element: https://en.wikipedia.org/wiki/Electronegativity---Because we have a combination of a non-metal and non-metal SO2 (Sulfur dioxide) is considered an covalent/molecular compound.In general, covalent compounds compounds:- have low melting points and boiling points.- have low enthalpies of fusion and vaporization.- do not conduct electricity when dissolved in water.For more chemistry help, see http://www.Breslyn.org. Use MathJax to format equations. (Read full article SO2 lewis structure). Due to this, it becomes tough for the valence electrons to easily bond with other electrons preferring shared format, that is, covalent bond. Carbon and oxygen are non-metals, thus we know carbon dioxide is a covalent compounds Another method is by calculating the difference in electronegative, we can determine the polarity of molecule. _____ are either positively charged or negatively charged species in which the number of protons and electrons are not equal. 3. There is a table on that page that says the PbO is "ionic". My aim is to uncover unknown scientific facts and sharing my findings with everyone who has an interest in Science. Which formulas represent ionic compounds and which represent covalent compounds? Classify each as ionic or covalent and name each compound. Save my name, email, and website in this browser for the next time I comment. As for shapes, you need to first draw a lewis dot structure (LDS) for the molecule. Several examples are found in Table 3.3.1. It can be studied very well with the help of the Lewis structure that says a double covalent bond exists between the oxygen atoms. Nitrogen monoxide (NO) will be a covalently bound molecule (two non-metals), silicon dioxide (SiO 2) will be a covalently bound molecule (a semi-metal and a non-metal) and MgCl 2 will be ionic (a metal and a non-metal). Table \(\PageIndex{1}\) lists these numerical prefixes. of 'neutral atoms' are considered and not of them with their oxidation states. Ionic vs. Covalent Compounds Airplane. By definition, an ionic bond is between a metal and a nonmetal, and a covalent bond is between 2 nonmetals. Ionization energy is another property that is responsible for the oxygen forming a covalent bond. Example: When 1M solution of NaOH and 1M solution of HCl are mixed, then product will be as follows; NoOH + HCl NaCl + H2O. Some of these properties are: At normal room conditions, ionic compounds stay in a solid state only, while covalent compounds can be present in a solid, liquid, or in the gas state. xcolor: How to get the complementary color. A covalent bond is formed when the electronegativity difference between two elements ranges between 0 (two of the same element bonding together) and 1.69 (almost ionic bonding). You can use determine the difference in electronegativty. Im a mother of two crazy kids and a science lover with a passion for sharing the wonders of our universe. For example, Na is 0.9 and Cl is 3.0 Then subtract to find the difference (3.0-0.9 = 2.1) Using this method, you can determine the value of each bond. If the LDS has 3 single bonds (or 2 single/1 double) and NO lone dot pairs, it's trigonal planar. Although there are no ions in these compounds, they are named in a similar manner to binary ionic compounds. Moreover, the double bond forming between two oxygen atoms consists of one sigma bond and one pi bond providing the stability to the oxygen molecule. Making statements based on opinion; back them up with references or personal experience. An electronegativity difference of anything from 0 (two of the same element bonding together) to 1.69 (a bond that is ALMOST ionic) will result in . If the difference is between 0.0-0.3: The bond is nonpolar covalent, If the difference is between 0.4-1.7 (Some books say 1.9): The bond is polar covalent. W O X 2 and W O X 3 have a covalent characteristic, and thus lower melting point than the metal. The atomic number of the oxygen is 8 by which its electronic configuration is 1s2 2s2 2p4. The ionic compound LiBrO is named: lithium bromide lithium bromate lithium bromite lithium (II) bromate The "lithium" part of this name is easy, but if you missed this question, you may want to review when to end a name with -ide, -ite, and -ate. Fundamentals of metallurgy Related titles: New developments in advanced welding (ISBN-13: 978-1-85573-970-3; ISBN-10: 1-85573-970-4) The elements in \(\ce{Na_2O}\) are a metal and a nonmetal, which form ionic bonds. Experts are tested by Chegg as specialists in their subject area. Therefore, the atoms form covalent bonds. The Beilstein Journal of Organic Chemistry is a peer-reviewed Open Access journal with no fees for authors. Normally, no prefix is added to the first elements name if there is only one atom of the first element in a molecule. Chemistry Stack Exchange is a question and answer site for scientists, academics, teachers, and students in the field of chemistry. Samantha T. George C. With this lets answer the question: So, Is O2 ionic or covalent? By definition, it is clear that electronegativity is directly proportional to the atomic size. If the chemical bond (electrostatic attraction) between them is ionic, the compound is called an ionic compound. Also, oxygen in liquid and solid form is pale blue in color which changes to orange, black, or red at low temperature and very high pressure. Containers may burst violently if exposed to fire or heat for a lengthy period of time. We have already encountered these compounds, but we list them here explicitly: Methane is the simplest organic compound. H-Cl bond, EN is 0.9, so the bond is polar covalent. which unfortunately I can't get at the moment, but I think the example in this link (, @Mithoron Obviously, that was too ignorant of me! Nitrogen trifluoride (NF3) is an odorless, colorless gas. Write a suitable formula for the following compounds. We learned that silicon dioxide causes no harm when consumed orally but is extremely hazardous if inhaled in large amounts. When we have a non-metal and. When dissolved in water, ionic compounds can conduct electricity due to the presence of free ions. Sulfur dioxide (SO2) is a covalent molecule. To determine whether a bond is Covalent or Ionic, you must know the difference in electronegativity (a fancy word for describing how good a job a particular element does at attracting new electrons). The molar mass of S =32.066 g/mol.O2 molar mass = 16.00 x 2 = 32.00 g/mol.Molar mass of SO2 = 64.066g/mol, Sulfur or iron pyrites are burnt in the air to produce SO2.S + O2 (gas) > SO2 (gas)4FeS2 + 11O2 > 2Fe2O3 (solid) + 8SO2 (gas). Earths crust is made up of around 59% silicon dioxide. Is a highly oxidized element more electropositive than a lesser oxidized counterpart? Identify the ion with the given number of protons and electrons. If the electronegativity difference is less than 2.00, the bond is ionic; If the electronegativity difference is between 0.4 and 2.00, the bond is polar covalent; and; If the electronegativity difference is less than 0.4, the bond is covalent. It is transparent to grey in color in its crystalline or amorphous powdered form. Differences in physical properties of covalent and ionic compounds. Oxygen is a colorless, tasteless, and odorless gas that is usually purified with the help of fractional distillation of the liquefied air. In IIT-JAM 2018, There was one question: "which one of the following oxides are ionic?" If you have any questions, feel free to comment or send an email to [email protected], There are two double bonds between the sulfur and oxygen atoms in the sulfur dioxide molecular geometry. Because sulfur and oxygen are both non-metals, the formation of sulfur dioxide is a covalent bonding process. Techiescientist is a Science Blog for students, parents, and teachers. what are the characteristics of ionic compounds high melting point, brittle, crystals, conductive, and disovlable. Be sure to answer all parts. document.getElementById( "ak_js_1" ).setAttribute( "value", ( new Date() ).getTime() ); Your email address will not be published. Depending on the types of elements interacting or bonding with each other, the type of chemical bond formed can be; ionic, covalent, hydrogen bond, or Vander Waal bond. See for ex. With one calculation you might get, say 47% of ionic character, with another mayyybe 53%, who knows? In band theory, a hole is generally regarded as an electron missing from the top of the valence band. Now, putting the values we will get the % ionic character of $\ce{PbO}$ to be 33.75%, which, unfortunately for you and me (I also appeared in this year IIT-JAM and submitted $\ce{PbO}$ to be ionic),indicates that $\ce{PbO}$ is predominantly covalent in character. Silicon dioxide is usually an amorphous crystalline solid as the arrangement and orientation of atoms are random in the network. As for shapes, you need to first draw a lewis dot structure (LDS) for the molecule. With this, the smaller the size of an atom, the less reactive it will be and will be closer to the positively charged nucleus. You'll get a detailed solution from a subject matter expert that helps you learn core concepts. Your email address will not be published. The bond is covalent and nonpolar when the difference is extremely tiny or nil. 5. Which reference should I send to them? answered 03/04/13. The two most basic types of bonds are characterized as either ionic or covalent. Covalent compound: CSF Cs C2H40 WO2 PCI3 NH4+ Nazo SO43- lonic compound: C6H5N CdBr2 N2 Cao This problem has been solved! When these two ions approach one another, they are attracted to each other. Also, the difference of electronegativity between nitrogen (N) and oxygen (O) atoms on the Pauling scale is not big enough to make an ionic bond in the NO2 compound. And what difference it would make? This difference results in an electron(s) being shared between the non-metals. Compounds that contain covalent bonds (also called molecular compounds) exhibit different physical properties than ionic compounds. Covalent and Ionic Virtual lab 2021-2022 worksheet activity University Doane University Course Organic Chemistry (CHM 203) 14 Documents Academic year:2021/2022 Uploaded byMarcia Murillo Helpful? The sigma bond of this double bond is responsible for providing a strong stable structure to the molecule. To learn more, see our tips on writing great answers. of $\ce{O}$ = 3.44. Pauling's e. value is much lower for Pb (+2), 1,87 according to, @Mithoron Yes, but in Hannay Smith equation, the e.n. Silicon dioxide is an odorless and tasteless compound. So you usually just look at the periodic table and determine whether your compound is made of a metal/nonmetal or is just 2 nonmetals. Although I know this distinction between ionic and covalent isn't defined sharply. Contents show What are ionic and covalent bonds? In alignment with this, atomic size is another property that promotes the formation of a strong covalent bond. Naming binary (two-element) covalent compounds is similar to naming simple ionic compounds. The only pure covalent bonds occur between identical atoms. Get a free answer to a quick problem. Does the oxygen molecule have a polar or nonpolar covalent bond? No packages or subscriptions, pay only for the time you need. The best answers are voted up and rise to the top, Not the answer you're looking for? Let us practice by naming the compound whose molecular formula is CCl4. Covalent bonds have transferred electrons and and stronger bonds *if the electronegativity is less than 1.67 it is usually considered covalent, and if greater, then ionic ** The farther apart the elements on the periodic table, the larger the electronegativity difference, the more ionic the bond, the more polar the bond and the stronger the bond. Such bonds are formed between a nonmetal and metal, where metal acts as electron donor and nonmetal acts as electron acceptor. So when they combine, it forms a covalent compound. Compounds Naming Reaction Equations and . This is a value that rates how attracted an electron is to a particular atom. For each of the following, stat whether it has covalent or ionic bonding. This value is often stated in a chart or on the periodic table. If it has 3 single bonds and one pair of lone dots, the shape is trigonal pyramidal. Together, they comprise a single ion with a 1+ charge and a formula of NH4+. a bond between atoms that transfers electrons to one another. However, workers and laborers working in mines and caves are prone to silica dust. I know many of you wonder if silicon melts. The formula of the carbonate ion is CO32. My answer to this question is to get a better textbook when one is available. high melting point, brittle, crystals, conductive, and disovlable. > Well, molarity is temperature-dependent, so I will assume #25^@ "C"# and #"1 atm"# and I got #~~# #"1 M"#, because you have only allowed yourself one significant figure And at these conditions, #rho_(H_2O) = "0.9970749 g/mL"#, so that, #400 cancel("g H"_2"O") xx "1 mL"/(0.9970749 cancel"g")#, #"M" = "mols solute"/"L solution"# (and NOT solvent! _________ ion is an example of a polyatomic anion. by Lzika. When the difference in electronegativity between the anion and the cation is between 0.4 and 1.7, such bonds occur.Check the full article hereIs SiCl4 polar or nonpolar?. a) HS bond in H2 S d) NO bond in NO2 b) SO bond in SO2 e) CCl bond in CCl4 c) MgBr bond in MgBr2 4. On the other hand, ionic bonds are non-directional for which the properties shown by covalent molecules do not hold any validity. I don't understand the purpose or the advantage of using an empirical equation, which is itself based on another empirical property (electronegativity), to try to obtain a precise quantification of percent ionic character. \[\text{moles solute} = \text{M} \times \text{L}\nonumber \]. As a result of the small variation in electronegativity between the two atoms, electron bonds are shared, producing covalent bonds. The oxygen molecule is covalently bonded where an equal number of valence electrons are shared by both the atoms. To meet this need, each oxygen atom shares two of its electrons with the other oxygen forming a strong oxygen-oxygen double shared covalent bond. Moreover, the oxygen molecule never catches fire and is not flammable being a strong oxidizer. Bonds can show much greater ionic character than would be expected from the electronegativity differential. As neither of both is strong enough to attract the shared pair of electrons towards itself. The definition above is fairly simplistic, but works much of the time. The balance of oxygen is maintained because it is exhaled by plants and inhaled by human beings and animals. Here is the article that I wrote on. 2. Moreover, oxygen is also an important part of various atmospheric cycles on the earth. However, within the polyatomic phosphate ion, the atoms are held together by covalent bonds, so this compound contains both ionic and covalent bonds. Short story about swapping bodies as a job; the person who hires the main character misuses his body. Kids often eat sand and soil while playing, which mostly consists of silica, but they do not cause any harm to their health. For a compound to be ionic, this difference should be greater than 2.0. In each bond, nitrogen is more electronegative than hydrogen. For instance, sodium chloride consists of sodium ions (positively charged) and chloride ions (negatively charged). BF3 is a non-polar compound. _______ are positively charged ions with more ______ than _________. A polyatomic ion is an ion composed of two or more atoms that have a charge as a group (poly = many). I just got carried away with this (. Both O and S have the same outer electric configuration of ns2 and np4. In order to form a covalent bond, the electronegativity value of the participating atoms must be high while the difference must be low which will make the molecule nonpolar. Different teachers and different books will use different terminology. Naturally, silicon dioxide is present in sand and rocks, which are extracted by mining. Whereas in the case of heteronuclear molecules, there will be some electronegativity difference, so they will form a polar covalent bond. Page Contents show m is the mass of KHP in grams. Whereas, covalent compounds do not conduct electricity in any state. Ionic: CdBr2, CaO, CsF, Na2O, WO2. De ce fait, la comprehension des processus biologiques qui s'operent au CHCl3, there may be bond "strain" and not all angles are equal, due to. Im a mother of two crazy kids and a science lover with a passion for sharing the wonders of our universe. Techiescientist is a Science Blog for students, parents, and teachers. The nomenclature of binary covalent compounds follows these rules: Inhaling fine particles of silica dust may lead to bronchitis, silicosis, and even lung cancer in cases of prolonged exposure. Na2Si3O7 + H2SO4 > 3SiO2 + Na2SO4 + H2O. By clicking Post Your Answer, you agree to our terms of service, privacy policy and cookie policy. Because of its bulky size and giant covalent structure, silicon dioxide is almost insoluble in water. The structural formula of NO3 is NO3-. What should I follow, if two altimeters show different altitudes? CHaCl ionic CaCk ionic & Covalent Study. In a CO2 molecule, between C and O, the difference is around 0.89, so we can call this a covalently bonded molecule. The compounds in each group below have similar looking formulas but they have very different names. CO2 (Carbon dioxide) is a covalent (nonpolar covalent) compound because when one nonmetal combines with another nonmetal, it usually forms a covalent compound. Sulfur and oxygen atoms with identical electronegativity try to link together. CO2 convalent to Naming Comp. The author has an hindex of 59, co-authored 274 publication(s) receiving 14531 citation(s). SO2 is a covalent molecule. This is a major reason why ionic bonding is only applicable to the solid-state. When we have a non-metal and a non-metal the compound is considered non-polar covalent.Because we have a non-metal and non-metal in N2 there will be no difference in electronegativity between the non-metal and non-metal. townhomes for rent in pg county. 3. O2 is a covalent molecule because each oxygen atom needs two valence electrons to complete its octet. By clicking Accept all cookies, you agree Stack Exchange can store cookies on your device and disclose information in accordance with our Cookie Policy. Required fields are marked *. Below is the molecular formula of ammonia, NH3. This makes SO2 a polar covalent molecule.In addition, the unbonded electrons on the sulfur and oxygen create repulsion between atoms.This is another cause of the polarity of the sulfur dioxide molecule. And if the LDS has 2 double bonds and NO lone dot pairs, or is just 2 atoms, the shape is linear. Hence, silica behaves like a covalent compound. For some simple covalent compounds, we use common names rather than systematic names. Why does the narrative change back and forth between "Isabella" and "Mrs. John Knightley" to refer to Emma's sister? These can be electron affinity, atomic size, ionization energy, and electronegativity. the difference in size between the terminal atoms. It is available in three forms: gaseous monomer, crystalline trimer, and solid polymer. Silicon dioxide is formed when isolated silicon is exposed to an abundant amount of oxygen. ab- Sugar and S. Ionic compounds g and Writing F. 7. CF4 makes 109.5 angle between any two F atoms and C. Due to symmetry all bond angles are equal. Ionic compounds -ionic 1.7+ Covalent compounds If the LDS has 4 surrounding atoms/4 single bonds and no lone dots on the central atom, the shape is tetrahedral. If the difference is between 1.7 and 2.0, the compound is polar covalent because there is slight charge domination in one of the atoms. Site design / logo 2023 Stack Exchange Inc; user contributions licensed under CC BY-SA. When the magnesium atom loses two electrons to create the Mg2+ ion and each chlorine receives one electron to form the Cl ion, an ionic bond is formed between the magnesium and chlorine atoms.Check Is MgCl2 ionic or covalent?. In this article we studied the types of elements, types of bonds that form covalent compounds and ionic compounds, then we formulated them on the basis of electronegativity differences between atoms. It is important to understand that sodium chloride is formed because of ionization. Silicone dioxide constitutes around 59% of the earths crust. The chemical formulas for covalent compounds are referred to as molecular formulas because these compounds exist as separate, discrete molecules. The difference in electronegativity between sulfur (S) and oxygen (O) atoms on the Pauling scale is not big enough to make an ionic bond in the SO2 compound. Decide if the following formulas represent Ionic or Covalent compounds. The portion of the molecule that contains both oxygen atoms is somewhat negatively charged. Here, it is important to know that only a shared covalent bond is formed in the molecule having two similar atoms. That is why wearing specialized masks with respirators is of utmost necessity for workers working in mines. The bond is polar covalent or ionic when it is big. While reacting with nonmetals, both form covalent compounds, for instance, H2O. As a result, SO2 is a covalent compound and slightly polar as well. The higher the electron affinity, the higher will be the affinity of the atom to accept the electrons. rev2023.5.1.43405. Whereas, on the other hand, nonpolar molecules are exactly opposite where no difference in electronegativity values exists creating the net dipole moment zero. Polar covalent bonds are those where the difference in electronegativity values exists. what is an ionic bond? As a general rule of thumb, compounds that involve a metal binding with either a non-metal or a semi-metal will display ionic bonding. In many cases, a strong ionic bonding character is driven by molecular-orbital structure rather than electronegativity. 35,000 worksheets, games, and lesson plans, Marketplace for millions of educator-created resources, Spanish-English dictionary, translator, and learning, Diccionario ingls-espaol, traductor y sitio de aprendizaje, a Question What elements make covalent bonds? The attraction between molecules (called intermolecular forces) will be discussed in more detail in Section 8.1. If the difference is between 0.0-0.3: The bond is nonpolar covalent. The reaction is depicted below where trisilicate and sulphuric acid are being used. it is a bond that results from 2 metals sharing electrons what is an alloy? Silicon dioxide is used as a fining agent in the beverage industry for manufacturing juices, beer, and wine. In BF3, the central boron atom has sp2 hybridized orbitals, resulting in an unfilled p orbital on the Bron atom and trigonal planar molecular geometry. The attraction between two particles is generally called a bond, Shape can mean two completely different things to two different teachers or textbooks. The total number of SO2 valence electrons is12. As far as question is concerned, there shouldn't be such option as this isn't clear case, but I'm afraid that you're wrong and they're right. + 3.5 ($ \Delta\ $E.N. whereas the portion that has the sulfur atom has a slightly positive charge. What is the molar mass for sulfur dioxide? This is due to the very strong attractions between the ionsin ionic compounds, the attractions between full charges are (much) larger than those . Making educational experiences better for everyone. Covalent: C6h5N, C2h4O, PCI3. Which formulas represent ionic compounds and which represent covalent compounds? Ionic Solids. By introducing the light element C atoms into the transition metal Mo to form a 'covalent metal' structure, the hardness and mechanical properties of the superconducting material can be . Even $\ce{PbCl2}$ is considered as Ionic according to many books, where chlorine is less electronegative and much bigger in size as compared to oxygen, So at least $\ce{PbO}$ should have more ionic character than $\ce{PbCl2}$ according to the Fazan's rule. Learn more about Stack Overflow the company, and our products. Sulfur hexafluoride (SF6) is a non-toxic gas that is used in a variety of applications due to its inert properties. To tell if N2 is ionic or covalent (also called molecular) we look at the Periodic Table that and see that N2 is made up of two non-metals. Sulfur dioxide (SO2) is a covalent molecule. There are mainly three types of elements present in the periodic table, these are; metals, nonmetals, and metalloids. An example problem on the paper is carbon tetrafluoride. This difference results in an electron(s) being shared between the non-metal atoms.. ---Helpful ResourcesMetals, Non-Metals on the P- Table: https://youtu.be/OoooStZQHdAIonic, Covalent, \u0026 Polar Covalent: https://youtu.be/OHFGXfWB_r4Electronegativity for each element: https://en.wikipedia.org/wiki/Electronegativity---Because we have a combination of a non-metal and non-metal N2 is considered a non-polar covalent compound.For more chemistry help, see http://www.Breslyn.org. In light of the same, each oxygen atom will try to accept the valence electrons because of which two oxygen atoms will share the valence electrons to complete their octet. It does not conduct electricity because it is a covalent compound. Thus a metal cation M2 could be regarded as a metal atom plus two localized holes (M 2 h). You'll get a detailed solution from a subject matter expert that helps you learn core concepts. But, is silicon dioxide ionic or covalent? Identify the ion with the given number of protons and electrons. Edit the PDF for free by using this toolbar. The two main types of chemical bonds are ionic and covalent bonds. W, 2 - 1/2 07 sp + vTv ) 3.37ft2 5-- = 11.0 eV . Two MacBook Pro with same model number (A1286) but different year. A system of numerical prefixes is used to specify the number of atoms in a molecule. 11 Uses of Platinum Laboratory, Commercial, and Miscellaneous, CH3Br Lewis Structure, Geometry, Hybridization, and Polarity. On sulfur, there is also a single pair of electrons.Between sulfur and each oxygen atom, one sigma and one pi bond are formed between sulfur and each oxygen atom. This difference creates an overall net dipole moment on the molecule by which separation of electric charges occurs, making two separates positively and negatively charged ends. To determine whether a bond is covalent or ionic, we must understand the difference in electronegativity. It is one of the metals widely used in making solar panels due to its conductivity. For example, both hydrogen and oxygen are nonmetals, and when they combine to make water, they do so by forming covalent bonds. Silicon dioxide finds its uses in abundant fields, ranging from natural to industrial.
