These crystals are usually brittle. 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. The formation of a covalent bond allows the nonmetals to obey the octet rule and thus become more stable. Draw the structure of these positive ions. (iii) An electrostatic force of attraction exist between the oppositely charged ions. Question 12: Why ionic compounds are generally soluble in water, but insoluble in organic solvents ? The four carbon hydrogen tetrahedral structure. Figures (b) and (c) show a sodium ion and a chloride ion has been pulled out of crystalline structure by water molecules. The arrow represents a co-ordinate bond. Select the correct option to test your skills on Chemical Bonding. How many electrons in the outer shell of a nitrogen atom are not involved in the formation of a nitrogen molecule ? Chemical bond is an attractive force which keeps tow atoms or ions together in a molecule. (iv) Electrovalent compounds are soluble in polar solvents. Answer: The important general characteristics of covalent compounds are as follows: (i) Usually covalent compounds exist in gaseous, liquid or amorphous state. Why ? Answer: Because they are short of octet in their outermost shell. Question 20: Why hydrogen chloride can be termed as a polar covalent compound ? Hence it is also called a semipolar bond or dotive bond. When the molecules of water bombard the sodium ion, such that the slightly negatively charged oxygen atom face sodium ion, then they exert an electrostatic pull on it. Under normal conditions, which physical state will the compound QS exist in ? 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. In such a configuration, none of the participating atoms is more electrically charged as compared to other atoms. Copyright © 2020 Entrancei. State the following : (i) the outer electronic configuration of Y. Atoms enter into chemical bonding to acquire the stable inert gas electronic configuration. Hence, it is a covalent compound. (ii) Give one property of magnesium chloride which agrees with it being an ionic compound. 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. They are reactive. 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. Answer: A molecule of HCl is a polar covalent, i.e., the electron pair shared between hydrogen and chlorine is far away from hydrogen than chlorine, with the result that hydrogen atom has a slight positive charge on it and the atom of chlorine has slight negative charge on it as, When hydrogen chloride is added to water, then water molecules bombard it from all directions. Chemical Bond. (iii) Except for graphite, covalent compounds are bad conductors of electricity. This test is totally based on latest Chemistry textbook of ICSE Board. (iii) High lattice energy: The higher is the value of lattice energy, greater will be the electrostatic force of attraction between the oppositely charged ions and hence ionic compounds are formed with greater ease by release of energy. Kossel-Lewis Approach to Chemical Bonding (ii) the valency of Y. (ii) Electrovalent compounds form hard crystals. 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. The molecules are made of two or more atoms joined together by some force acting between them. In dry state, it is bad conductor of electricity. Further, since the number of protons remains the same as in the neutral atom, the nucleus attracts the increased number of electrons less strongly. (ii) Covalent compounds have low melting or boiling points. In NH3 molecule each of three H-atoms is linked to N-atom by a covalent bond. Thus in this molecule N-atom is left with a lone pair of electrons after completing its. Question 4: What are the salient features of electrovalency ? with a release of energy. Chapter 10: Chemical Bonding Ch 10 Page 1 . Answer: Formation of Hydronium ion, H3O+ : This ion formed by the combination of H2O molecule and H+ ion. (iv) It does not conduct electric current in the solid state but conducts electric current in the molten or dissolved state. Answer: The water molecules have high dielectric constant thus, water molecules easily break the ionic bonds between the ions. Question 2: Write the general characteristics of electrovalent compounds. (iii) These compounds are soluble in non-polar solvents and insoluble in polar solvent. They tend to attain eight electrons in their outermost shell to acquire nearest inert gas electronic configuration. (b) Covalent bond. 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. Metals with lower ionisation energy values have a greater tendency to form ionic bonds. Whereas Liquid CCl4 does not contain any charged particles to conduct electricity. Hence in H3O+ ion all the three bonds are identical. (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. This test module contains five questions in fill in the blanks format. Answer: A covalent bond between two atoms is non-polar if the electrons involved in bond formation are equally shared between two atoms having similar electronegativities. Question 2: Why do certain elements form ions ? In what kind of compound does this effect occur ? (vi) They react very fast. Question 11: Why do electrovalent compounds usually dissolve in water and molecular compounds dissolve in organic solvents ? Question 4: Why a molecule of hydrogen is more stable than the uncombined atoms ? Question 19: Why do covalent compounds exist as gases, liquids or soft solids ? After the formation O→ H+ co-ordinate bond becomes identical to the two O—H covalent bonds. Covalent bonds are a class of chemical bonds where valence electrons are shared between two atoms, typically two nonmetals. Free download of step by step solutions for class 10 Science chapter 2 - Chemical Bonding of ICSE Board (Concise - Selina Publishers). Negative ions —> Anions (Cl–, O2-, N3-, etc.) octet by sharing three of its valence shell electrons with three H-atoms. Thus, a chemical bond is defined as a force that acts between two or more atoms to hold them together as a stable molecule. Question 14: Why is sodium ion (Na+) not reactive, but sodium metal is very reactive ? (iv) Which property of the above compound agrees with the being of a covalent compound ? Answer: (i) Y has six electrons in its valence shell. Answer: Molten NaCl contains Na+ and Cl– ions, which are free to move, hence it conducts electricity. TIP: I project the Chemical Bond Properties Chart and have the students copy down the properties of bonds before they perform the lab. Tendency of atoms to attain stable configuration of eight electrons in their valence shell is cause of chemical combination. The acceptor atom must have an empty orbital to accept the lone pair of electrons. Question 5: Write important general characteristics of covalent compounds. As atoms of all elements except the noble gases, have one to seven electrons in their outermost shell, therefore, they are not in the state of minimum energy. Answer: The crystals of electrovalent compounds are made up of crystal lattice containing oppositely charged ions. This student-centered station lab is set up so students can begin to explore chemical bonding. For webquest or practice, print a copy of this quiz at the Chemistry: Chemical Bonding webquest print page. (ii) It is rigid and has directional properties. 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. (iii) Hydrogen chloride. CHEMICAL BONDING AND MOLECULAR STRUCTURE OCTET RULE-During a chemical reaction the atoms tend to adjust their electronic arrangement in such a way that they achieve 8 e-in their outermost electron. Question 13: How is a co-ordinate bond formed? This is second set of fill in the blanks test on Chemical Bonding. The molecules possessing lower energy are more stable, than the atoms. The following section consists of Chemistry Multiple Choice questions on Chemical Bonding For competitions and exams. Answer: Pure covalent bond exists between two elements which have similar electronegativities. . Question 9: Why electrovalent compounds have high melting, boiling points and low volatility ? A molecule is formed if it is more stable and has lower energy than the individual atoms. Electro-negativity of hydrogen = 2.1, Question 2: With the help of the figure Show HCl is-a polar molecule. (iv) Can Q and S, both be metals ? Answer: (1) Hydrogen chloride and hydrogen bromide. Forming Covalent Bonds. Compound formed due to this bond is called covalent compound. Thus, the ionic compounds do not dissolve in them. 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. However, if you experience any difficulties, follow the following steps: 1.) Back to Science for Kids (b) A bond formed by a shared pair of electrons, each bonding atom contributing one electron to the pair. (iii) the bonding present in H2Y. In liquids, the molecules are weakly attracted whereas in gases, these forces are almost non¬existent. (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. A-1, Acharya Nikatan, Mayur Vihar, Phase-1, Central Market, New Delhi-110091. Thus H3O+ ion contains two O—H covalent bonds and one O— H co-ordinate bond. Thus, there are large inter molecular spaces between the molecules. Question 12: (i) Name two compounds that are covalent when taken pure but produce ions when dissolved in water. What is a chemical bond ? CC bond length is shorter than C=C bond which in turn is shorter than C-C. H+ ion has one vacant ls-orbital. Answer: The force of attraction between the molecules is very weak and so the amount of energy needed to separate them is small, consequently they have low melting points and boiling points. Free PDF download of Important Questions for CBSE Class 11 Chemistry Chapter 4 - Chemical Bonding and Molecular Structure prepared by expert Chemistry teachers from latest edition of CBSE(NCERT) books. (iii) Electrovalent compounds have high density with high melting and boiling points. Valency: Valency is the main point on which chemical bonding depends. Answer: Lone pair of electrons is the unshared pair of electrons left on the atom in a covalent molecule Question 2. (vi) These are stable compounds. Chemical bonding is one of the key and basic concepts in chemistry. Answer: Some salient features of electrovalency are mentioned below : (i) An electrovalent bond is formed by loss or gain or transfer of electrons. Answer: Sodium ion has eight electrons in its valency shell and it is the minimum state of energy, while the sodium metal has one electron in valency shell, so the sodium metal is very reactive. In the second step the two electrons, one each with A and B- are shared by both the ions. To be very honest, chemical bonding is the only chapter which is too easy to study. Draw an electron dot diagram of a hydronium ion (with lone pair). Set 1 Question 18: Why most of the covalent compounds have density less than that of water ? Answer: Every particle (molecule, atom or ion) has the tendency to attain the state of lowest energy. Question 3: Why are all atoms other then noble gas atoms, reactive ? 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. So, it is smaller than the atom. (iii) Name one compound which is covalent, but on dissolving in water conducts electricity ? The four carbon hydrogen bonds are directed towards the four corners of tetrahedron. This makes the shell expand outward. 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. Answer: Covalent compounds exists as gases, liquids or soft solids because they have weak forces of attraction between their molecules. Answer Question 15: Which conditions are necessary for the formation of co-ordinate bond? (iii) Solid state. Practice for next class: Bond Polarity One atom pulls the electrons in the bond closer to its side. Question 16: Explain the formation of H3O+ and NH4+ ion. Elements with high electron affinity values form ionic compounds. (ii) In the formation of electrovalent compounds, electrons are transferred from one element to another. However, it is not actually known that how many molecules of water are necessary to pull out a particular ion from its crystal. (iv) No. (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. 1Å = 10-10m and 1pm = 10-12 m. It is determined with the help of X-rays diffraction and other spectroscopic methods. Answer: The general characteristics of co-ordinate compounds are as follows: (i) Co-ordinate compounds are identical to normal covalent compounds. Justify your answer. It donates its valence electron, the residual ion consists of a single proton. Question 20: Predict the type of bonding in the following molecules : (i) Oxygen (ii) Calcium oxide (iii) Water (iv) Methane (v) Ammonium ion (vi) Nitrogen (vii) Magnesium chloride (viii) Carbon dioxide (ix) Carbon tetra chloride (xi) Hydrogen cyanide (x) Hydrogen chloride Answer: (i) Covalent bond (ii) Ionic bond (iii) Covalent bond (iv) Covalent bond (v) Covalent bond (vi) Ionic bond (vii) Covalent bond (viii) Covalent bond (ix) Covalent bond (xi) Covalent and co-ordinate bonds (x) Covalent bond, Question 1: With the help of the figure, explain that methane molecule is a non-polar covalent compound ? Question 5: Why is hydrogen ion called proton? The electrons of lone pair on N-atom are donated to H+ ion and thus a N/EH co-ordinate bond is established in NH4+ ion. CHEMICAL BOND- the chemical force which keeps the atoms in any molecule together is called a chemical bond. Chemical Bonding ICSE Class-10 Concise Chemistry Selina Solutions Chapter-2. Answer: NH3 has one lone pair of electrons which is donates to hydrogen atom forming a co-ordinate bond. (iv) Hydrogen chloride is a gas. Just follow the NCERT Textbook. Answer: (ii) Because carbon tetrachloride is non-polar covalent compound whereas water is a polar covalent solvent. (iii) has four electrons in its valence shell ? Answer: In covalent compounds, the molecules are held together by weak Van der Waal’s forces. Question 10: A compound has the formula H2Y (Y = Non-metal). 3) Coordinate bond is the bond formed between two atoms by sharing a pair of electrons, provided entirely by one of the combining atoms but shared by both . Properties: (i) It is hard and brittle. Chemical Bonding and Molecular Structure-class XI 1. (v) The melting and boiling points are higher than covalent compounds and lower than ionic compounds. Question 3: Explain how polar covalent compound HCl which is a bad conductor in pure and liquid state, ionises in water. Chemical Bonding AndMolecular Structures 2. Octet Rule. (iv) There is one fixed direction in space among the ions. Question 7: In the formation of compound XY2, atorix X gives one electron to each Y atom. (ii) For each compound, give the formulae of the ions formed in aqueous solutions. Each cation is surrounded by a definite number of anions and vice-versa. This result in that atom A develops unit positive charge and atom B develops a unit negative charge. You can download the Class 10 Chemistry ICSE Textbook Solutions with Free PDF download option. (iii) Give the structure of hydroxyl ion. 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. These ions occupy fixed position in the crystals and do not move when an electric field is applied. If the alignment of a water molecule is such that slightly negative oxygen atom faces the slightly positive hydrogen atom of HCl then, the slightly positive hydrogen atom is swallowed by water molecule in the form of single proton to form hydronium ion (H+3O). Bond length depends upon the following factors: Bond Multiplicity Bond length decreases with increase in bond multiplicity. Chemical bonding: Atoms, molecule or ions or different elements except the noble, do not have complete or stable octet so they combine with another element to complete its octet, this process of completing its octet by combining with other element is known as chemical bonding. Question 19: (i) Acids dissolve in water to produce positively charged ions. Atoms are held together and which is a polar covalent solvent H co-ordinate bond Y and Z have atomic 6. 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