Forming Covalent Bonds. Due to these strong forces of attraction, ionic compounds have high melting and boiling points and low volatility. Question 18: (i) Which of the following is not a common characteristic of an electrovalent compound ? In other words the number of molecules per unit volume is less. (iii) Electrovalent compounds have high density with high melting and boiling points. Metals with lower ionisation energy values have a greater tendency to form ionic bonds. Thus, hydrogen chloride can be termed as a polar covalent compound. Metals can only lose electrons to provide +ve ions. Thus H3O+ ion contains two O—H covalent bonds and one O— H co-ordinate bond. Chemical Bond. Answer: The crystals of electrovalent compounds are made up of crystal lattice containing oppositely charged ions. Introduction to chemical bonding Chemical Bonding of Class 10. Choose […] two atoms are A and B—in the first step the donor atom A transfers one electron of its lone pair to the acceptor atom B. Question 10: Why electrovalent compounds in crystalline state do not conduct electricity ? Question 7: In the formation of compound XY2, atorix X gives one electron to each Y atom. Hence, they are generally liquids or gases. (ii) It is soluble in water. Octet Rule. Give two limiations of this rule. Question 8: By drawing an electron dot diagram, show the lone pair effect leading to the formation of ammonium ion from ammonia gas and hydrogen ion. (vi) They react very fast. Marks and answers are given immediately. You can download the Class 10 Chemistry ICSE Textbook Solutions with Free PDF download option. Answer: When the unshared pair of electrons around an atom in the middle of a molecule is completely shared by another atom or an ion, it is called lone pair effect. (ii) Give one property of magnesium chloride which agrees with it being an ionic compound. Similarly, if the molecules of water bombards the chloride ion, such that the slightly positively charged hydrogen atoms face chloride ion then they exert an electrostatic pull on it. Question 8: There are three elements E, F, G with atomic numbers 19, 8 and 17 respectively. Question 19: Why do covalent compounds exist as gases, liquids or soft solids ? Practice for next class: Bond Polarity One atom pulls the electrons in the bond closer to its side. Give four properties of XY2. Chemical Bonding and Molecular Structure-class XI 1. (iv) Can Q and S, both be metals ? Answer: A co-ordinate bond is a union of one electrovalent and one covalent bond, the volatility of these compounds lies between that of covalent and ionic compounds. State the following : (i) the outer electronic configuration of Y. Thus, there are large inter molecular spaces between the molecules. Atoms enter into chemical bonding to acquire the stable inert gas electronic configuration. Why ? Answer: Every particle (molecule, atom or ion) has the tendency to attain the state of lowest energy. It is on account of this fact, that hydrogen ion is called proton. (ii) It is rigid and has directional properties. Question 17: Why covalent compounds have low melting point and boiling point ? (ii) In the formation of electrovalent compounds, electrons are transferred from one element to another. Answer: (i) (d) (ii) (a) Co-ordinate bond. Draw the structure of these positive ions. For example: A fluorine atom has seven valence electrons. Question 4: What are the salient features of electrovalency ? Answer: There is a strong force of attraction among the oppositely charged ions in the crystals of electrovalent compounds. Chapter 10: Chemical Bonding Ch 10 Page 1 . (ii) the valency of Y. Question 5: Why is hydrogen ion called proton? (ii) Ions are formed during the formation of an electrovalent bond. Answer: (i) Y will form an anion (ii) Z forms a cation (iii) X has four electrons in its valence shell. What is a lone pair of electrons. For these reasons the anion is bigger than the parent atom. (iii) The electronic configuration of nitrogen is 2, 5. (iv) There is one fixed direction in space among the ions. (v) The melting and boiling points are higher than covalent compounds and lower than ionic compounds. During the formation of H3O+, one pair of lone pair from O-atom is donated to the vacant ls-orbital of H+ ion and O — H co-ordinate bond is formed. Answer: In the formation of a cation, the atom loses the electrons of its outer shell. Register online for Chemistry tuition on Vedantu.com to score more marks in your examination. Hence it is also called a semipolar bond or dotive bond. Answer: In covalent compounds, the molecules are held together by weak Van der Waal’s forces. (iv) In the formation of magnesium chloride (by direct combination between magnesium and chlorine), name the substance that is oxidised and the substance that is reduced. Set 1 Answer: The cause of chemical combination between atoms of the various elements is their tendency to acquire nearest stable noble gas configuration of octet of electrons and duplet of electrons in case of hydrogen atoms in their outermost shells. In such a configuration, none of the participating atoms is more electrically charged. Lone pair effect is shpwn by polar covalent compounds such as HCl and NH3. Explore the causes, effects, and solutions to ozone layer depletion only at BYJU'S. Question 1: Why atoms combine with one another ? Chemical Bonding ICSE Class-10 Concise Chemistry Selina Solutions Chapter-2. About this quiz: All the questions on this quiz are based on information that can be found at Chemistry: Chemical Bonding. (ii) Magnesium chloride in the molten state or in aqueous solution is a good conductor of electricity and therefore is an ionic compound. Chemical bonding is one of the key and basic concepts in chemistry. If sufficient number of water molecules strike a particular sodium ion in same fashion, then it can be pulled out of the crystal of sodium chloride to form free sodium ion. Most of the substances found in nature are in the form of clusters or aggregates of atoms. The three dimensional structure of methane molecule has the carbon atom at the centre of the tetrahedron and four hydrogen atoms are located at the corners of the tetrahedron. Here we have covered Important Questions on Chemical Bonding and Molecular Structure for Class 11 Chemistry subject.. Chemistry Important Questions Class 11 are given below. Question 9: Why electrovalent compounds have high melting, boiling points and low volatility ? CHEMICAL BOND- the chemical force which keeps the atoms in any molecule together is called a chemical bond. Answer: NH3 has one lone pair of electrons which is donates to hydrogen atom forming a co-ordinate bond. This test is totally based on latest Chemistry textbook of ICSE Board. Copyright © 2020 Entrancei. (iii) It has high melting and boiling point. Answer: The formation of co-ordinate bond between two atoms to occur in the following two steps: E.g. They tend to attain eight electrons in their outermost shell to acquire nearest inert gas electronic configuration. For webquest or practice, print a copy of this quiz at the Chemistry: Chemical Bonding webquest print page. Bond length depends upon the following factors: Bond Multiplicity Bond length decreases with increase in bond multiplicity. Lewis symbols : The electrons present in the outermost energy level of an atoms and known as valence electrons. In what kind of compound does this effect occur ? (ii) High electron affinity: Higher the value of electron affinity, greater will be the tendency of the atom to gain electron and form an anion. This test module contains five questions in fill in the blanks format. (i) Classify the elements as metals and non-metals. Chemical Bonding is a chapter of ICSE class 10 Chemistry textbook. Question 3: Explain how polar covalent compound HCl which is a bad conductor in pure and liquid state, ionises in water. One end of the bond … Question 14: Why is sodium ion (Na+) not reactive, but sodium metal is very reactive ? Question 13: Why molten NaCl conduct electricity but, CCl4 does not ? These crystals are usually brittle. Noble gases are considered stable because they do not react with other elements. This result in that atom A develops unit positive charge and atom B develops a unit negative charge. Valency: Valency is the main point on which chemical bonding depends. Electro-negativity of carbon = 2.5 . Figures (b) and (c) show a sodium ion and a chloride ion has been pulled out of crystalline structure by water molecules. Elements with high electron affinity values form ionic compounds. Answer: Pure covalent bond exists between two elements which have similar electronegativities. Answer: The water molecules have high dielectric constant thus, water molecules easily break the ionic bonds between the ions. All exercise questions are solved & explained by expert teacher and as per ICSE board guidelines. Answer: (1) Hydrogen chloride and hydrogen bromide. The molecules are made of two or more atoms joined together by some force acting between them. Why ? Question 18: Why most of the covalent compounds have density less than that of water ? (iii) Except for graphite, covalent compounds are bad conductors of electricity. Chemical Bonding and Bond Theories; Molecular Structures and Theories; Hydrogen Bonding; The attractive force which holds together the constituent particles (atoms or molecules) in chemical species is known as chemical bond. Four of the stations are considered input stations where students are learning new information about chemical bonding, and four of the stations are output stations where students will be demonstrating their mastery of the input stations. In the second step the two electrons, one each with A and B- are shared by both the ions. Draw the Lewis structures for the following molecules and ions: H2S, SiCl BeF2, C03, HCOOH. Answer: In HCl molecule the strong nuclear charge of chlorine atom attracts the electron of hydrogen far away from its nucleus, with the result the hydrogen atom develops a slight positive charge (d+) and chlorine atom develops a slight negative charge (d–). Pass out a copy of Chemical Bonds Lab to each student. Answer: Because they are short of octet in their outermost shell. Which are : (i) forms an anion (ii) forms a cation ? Hence methane molecule is a non polar covalent compound. Question 6: (i) Name the charged particles which attract one another to form electrovalent compounds. Bond forms to get the stability. Thus their melting and boiling points are higher than covalent compounds and lower than ionic compounds. Answer: (i) Cation and anion (ii) There is a mutual sharing of electrons (iii) 2 (iv) Magnesium is oxidised and chlorine is reduced. The four carbon hydrogen bonds are directed towards the four corners of tetrahedron. ; Assemble and test the electrical testing kit. Question 5: Write important general characteristics of covalent compounds. Kossel-Lewis Approach to Chemical Bonding Question 13: How is a co-ordinate bond formed? (ii) Electrovalent compounds form hard crystals. Tendency of atoms to attain stable configuration of eight electrons in their valence shell is cause of chemical combination. Answer: The general characteristics of co-ordinate compounds are as follows: (i) Co-ordinate compounds are identical to normal covalent compounds. Download Formulae Handbook For ICSE Class 9 and 10. Answer: The important general characteristics of covalent compounds are as follows: (i) Usually covalent compounds exist in gaseous, liquid or amorphous state. For example, in case of methane molecule, the four electron pairs shared between one carbon atom and four hydrogen atoms lie exactly in between one carbon atom and four hydrogen atoms and hence forms non-polar bonds. 2) Covalent Bond: The chemical bond formed between two combining atoms by mutual sharing of one or more pairs of electrons. Answer: Water is polar molecule.%It hydrates ions by its polar attraction and pulls the ions apart. Answer: It has been found that a methane molecule has a three dimensional tetrahedral structure. The molecules possessing lower energy are more stable, than the atoms. Answer: The bond in XY2 is ionic. Answer: When an atom forms an anion, it gets one or more electrons (from another atom) in its outer shell. Answer: The covalent compounds do not have positive or negative ions in their fused state. Question 20: Why hydrogen chloride can be termed as a polar covalent compound ? all rights reserved. Chemical Bonding AndMolecular Structures 2. 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Question 15: Why covalent compounds are generally liquids or gases ? Any such aggregation in which atoms are held together and which is electrically neutral is called a molecule. Here you can get Class 11 Important Questions Chemistry based on NCERT Text book for Class XI.Chemistry Class 11 Important Questions are very helpful to score high marks in board exams. (ii) 2 (iii) Covalent (iv). Answer: Electrovalent crystalline solids do not conduct electricity because the oppositely charged ions in them are held together by a strong electrostatic force of attraction. Question 12: (i) Name two compounds that are covalent when taken pure but produce ions when dissolved in water. This is called octet rule. This charge is known as formal charge. Question 5: Draw dot diagrams to illustrate the structure of the molecules of: (i) Ammonia (ii) Carbon dioxide (iii) Methane (iv) Water Answer: Question 6: Give the electron dot structures of: (i) NaCl (ii) MgCl2 (iii) CaO (iv) Cl2 (v) H2O (iv) NH3 Answer: Question 7: Draw an electron dot diagram to show the structure of hydronium ion. To begin, students: Complete the Chemical Bond Properties Chart - BLANK document. Question 6: A cation is smaller than the atom from which it is formed. Answer: Lone pair of electrons is the unshared pair of electrons left on the atom in a covalent molecule Question 2. The ions drift in water in all possible directions and hence, ionic compounds dissolve in water, while organic solvents are non-polar in nature and hence, cannot break the ionic bonds. However, it is not actually known that how many molecules of water are necessary to pull out a particular ion from its crystal. (vi) These are stable compounds. State the type of bonding present in it. In this process, they become charged particles or ions. Therefore, a large amount of energy is required to separate them. This is similar to the formation of covalent bond. (iv) Hydrogen chloride is a gas. (ii) It cannot explain the formation of molecules such as PF5, SF6 etc., in which central atom has more than eight electrons in its valence shell. RS Aggarwal Solutions for class 7 Math's, lakhmirsingh Solution for class 8 Science, PS Verma and VK Agarwal Biology class 9 solutions, Lakhmir Singh Chemistry Class 9 Solutions, CBSE Important Questions for Class 9 Math's pdf, MCQ Questions for class 9 Science with Answers, Important Questions for class 12 Chemistry, Important Questions CBSE Class 10 Science. Attraction and pulls the ions apart a methane molecule is a non polar solvents down the properties of bonds they! Y and Z have atomic number 6, 9 and 10, it gets one or pairs! In a molecule the key and basic concepts in Chemistry a great force. 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