Question 1

Question 4Define each of the following terms -(a) electrovalent bond(b) electrovalent compound(c) covalent bond(d) covalent compoundwith suitable examples wherever required.

Accepted Answer

(a) The chemical bond formed between the two atoms by transfer of one or more electrons from the atom of a metallic element to an atom of a non-metallic element is called an electrovalent bond.(b) The chemical compound formed as a result of transfer of one or more electrons from the atom of a metallic element to an atom of a non-metallic element is called an electrovalent compound. e.g., NaCl, CaO(c) The chemical bond formed due to mutual sharing of electrons between the given pairs of atoms of non-metallic elements is called a covalent bond.(d) The chemical compound formed due to mutual sharing of electrons between the given pair of non-metallic elements is called a covalent compound. e.g., Chlorine molecule, Oxygen molecule.

Question 2

Question 6Sodium chloride is formed as a result of - transfer of electrons from metallic sodium atom to non-metallic chlorine atom. With the help of atomic orbit structure diagram - show the formation of sodium chloride [Atomic numbers: Na = 11, Cl = 17].

Accepted Answer

Atomic orbit structure diagram of the formation of sodium chloride by transfer of electrons from metallic sodium atom to non-metallic chlorine atom is shown below:

Question 3

Question 7Atomic number of calcium is 20 and of oxygen is 8. State the number of electrons - calcium loses and oxygen gains to attain stable electronic configuration of the nearest noble gas - during formation of electrovalent molecule, calcium oxide.

Accepted Answer

Calcium oxide is formed as a result of transfer of two valence electronsfrom metallic calcium atom 4020Ca; electronic configuration - 2,8,8,2 ; Nearest noble gas = Argon [2,8,8,]to non-metallic oxygen atom 168O - electronic configuration - 2,6 ; Nearest noble gas = Neon [2,8]calcium loses two electrons - from it's outer shell to attain stability of nearest noble gas - argon and becomes a calcium ion [cation] : Ca2+oxygen accepts two electrons - in outer shell to attain stability of nearest noble gas - neon and becomes an oxide ion [anion] : O2-

Question 4

Question 8Explain with the help of atomic orbit structure diagram the formation of calcium oxide.

Accepted Answer

Atomic orbit structure diagram of the formation of calcium oxide is shown below:Calcium oxide is formed as a result of transfer of two valence electronsfrom metallic calcium atom 4020Ca; electronic configuration - 2,8,8,2 ; Nearest noble gas = Argon [2,8,8,]to non-metallic oxygen atom 168O - electronic configuration - 2,6 ; Nearest noble gas = Neon [2,8]calcium loses two electrons - from it's outer shell to attain stability of nearest noble gas - argon and becomes a calcium ion [cation] : Ca2+oxygen accepts two electrons - in outer shell to attain stability of nearest noble gas - neon and becomes an oxide ion [anion] : O2-

Question 5

Question 11Draw the atomic orbit structure diagram for formation of -(a) hydrogen molecule(b) chlorine molecule(c) oxygen molecule(d) nitrogen molecule[at. no. H=1, Cl=17, O=8, N=7]

Accepted Answer

(a) Atomic orbit structure diagram for formation of hydrogen molecule is shown below:(b) Atomic orbit structure diagram for formation of chlorine molecule is shown below:(c) Atomic orbit structure diagram for formation of oxygen molecule is shown below:(d) Atomic orbit structure diagram for formation of nitrogen molecule is shown below:

Question 6

Question 12Give reasons for formation of single covalent bond between two chlorine atoms and a double covalent bond between two oxygen atoms - during formation of a covalent chlorine molecule and formation of a covalent oxygen molecule, respectively.

Accepted Answer

Atomic number of Cl is 17 and elect. config. is [2,8,7]. As both the Cl atoms require one electron to complete it's octet, hence, they both will share 1 electron and will attain a stable electronic configuration of the nearest noble gas — argon. Therefore, single covalent bond is formed during formation of a chlorine molecule.Atomic number of O is 8 and elect. config. is [2,6]. As both the O atoms require two electrons to complete their octet, hence, they both will share 2 electrons and will attain a stable electronic configuration of the nearest noble gas — neon. Therefore, double covalent bond is formed during formation of a oxygen molecule.

Question 7

Question 13Draw the atomic orbit structure diagram for formation of a -(a) water molecule(b) ammonia molecule[at. no. H=1, O=8, N=7]

Accepted Answer

(a) Atomic orbit structure diagram for formation of water molecule is shown below:(b) Atomic orbit structure diagram for formation of ammonia molecule is shown below:

Question 8

Question 14State why water has two lone pairs of electrons in it's covalent molecule while ammonia has one lone pair.

Accepted Answer

Water contains two hydrogen atoms and one oxygen atom. The hydrogen atom [1] has one electron in it's valence shell while the oxygen atom [2,6] has 6 electrons in it's valence shell. Two hydrogen atom share one electron each and two unshared pairs of electrons are left as lone pairs as shown in the diagram below :In the case of ammonia, it contains three hydrogen atoms and one nitrogen atom. Nitrogen atom [2,5] has five valence electrons and hydrogen atom [1] has one valence electron. In ammonia, each of the three hydrogen atoms are bonded to the nitrogen atom by a pair of shared electrons. Thus, the nitrogen atom in ammonia is left with one lone pair of electrons as shown in the diagram below:

Question 9

Question 15With the help of an atomic orbit structure diagram - explain the formation of :(a) carbon tetrachloride(b) methane[at. no. : C=6, Cl=17, H=1]

Accepted Answer

(a) Atomic orbit structure diagram for formation of carbon tetrachloride molecule is shown below:(b) Atomic orbit structure diagram for formation of methane molecule is shown below:

Question 10

Question 16Give a reason why one atom of carbon shares four electron pairs, one with each of the four atoms of chlorine during the formation of covalent molecule - carbon tetrachloride.

Accepted Answer

Carbon [At. no. 6, electronic configuration 2,4] needs four electrons to attain the electronic configuration of nearest noble gas — Neon. Chlorine atom [At. no. 17, electronic configuration 2,8,7] needs one electron to attain stable electronic configuration of nearest noble gas — Argon. Hence, to attain octet one atom of carbon shares four electron pairs, one with each of the four atoms of chlorine and forms covalent molecule carbon tetrachloride.

Question 11

Question 1(2005)Compound X consists of molecule.(i) Bonding in X will be:A: ionicB: electrovalentC: covalentD: molecular

Accepted Answer

CovalentReason — As compound X consists of molecules, it means that compound X is a Covalent compound (electrovalent compounds consists of ions) hence bonding in X is covalent.

Question 12

Question 1(2007)The electronic configuration of nitrogen is 2,5. How many electrons in the outer shell of a nitrogen atom are not involved in the formation of a nitrogen molecule.

Accepted Answer

Nitrogen has 5 electrons in the valence shell whereas it forms triple bond to fulfill it's octet and hence, 2 electrons are left in the outer shell of a nitrogen atom which are not involved in the formation of a nitrogen molecule. Formation of a Nitrogen molecule from Nitrogen atoms is shown in the below diagram:

Question 13

Question 1(2009)Draw the atomic orbit structure of carbon tetrachloride and state the type of bond present in it.

Accepted Answer

Atomic orbit structure of carbon tetrachloride is shown below:Type of bond present in carbon tetrachloride is Covalent Bond

Question 14

Question 1(2015)Explain the bonding in methane molecule.

Accepted Answer

Methane consists of one carbon atom [2,4] and four hydrogen atoms [1]. Carbon needs four electrons to attain a stable electronic configuration of nearest noble gas - Ne, whereas, hydrogen needs one electron to attain stable electronic configuration of nearest noble gas - He.Therefore, one atom of carbon shares four electron pairs one with each of the four hydrogen atoms, resulting in formation of methane molecule.The atomic orbit structure diagram of the formation of methane molecule is shown below:

Question 15

Question 2Give reasons for the following :To attain stable electronic configuration of the nearest noble gas —Hydrogen atom 11H — needs one electron.Oxygen atom 168O — needs two electrons.Nitrogen atom 147N — needs three electrons.Carbon atom 126C — needs four electrons.Chlorine atom 3517Cl — needs one electron.

Accepted Answer

As the atomic number of H is 1 and electronic configuration is 1, it needs one electron to attain nearest noble gas He configuration i.e. 2 electrons in first valence shell (Duplet-rule).As the atomic number of O is 8 and electronic configuration is 2,6 it needs two electrons to attain nearest noble gas Ne configuration i.e. 8 electrons in valence shell (Octet-rule).As the atomic number of N is 7 and electronic configuration is 2,5 it needs three electrons to attain nearest noble gas Ne configuration i.e. 8 electrons in valence shell (Octet-rule).As the atomic number of C is 6 and electronic configuration is 2,4 it needs four electrons to attain nearest noble gas Ne configuration i.e. 8 electrons in valence shell (Octet-rule).As the atomic number of Cl is 17 and electronic configuration is 2,8,7 it needs one electron to attain nearest noble gas Ar configuration i.e. 8 electrons in valence shell (Octet-rule).

Question 16

Question 6The representation below shows the outline formation of an electrovalent compound.If the atomic number of element 'X' is 11 and of element 'Y' is 17 —State why an electron is transferred from 'X' to 'Y' during the formation of 'X Y'Give a reason why electrons are not shared between 'X' & 'Y' — during the formation of 'XY'State the difference between 'X' and 'X1+'Does 'Y1-' have a stable or an unstable electronic configuration.If a compound is formed from atom A [at. no.19] and an atom Y [at. no. 17], would the compound 'AY' be an electrovalent or covalent compound. Give reasons.

Accepted Answer

As the electronic configuration of X is [2,8,1] and Y is [2,8,7], hence X donates one electron and Y accepts one electron in order to attain stable octet configuration. Hence, electron is transferred from X to Y.Sharing of electrons mainly takes between a pair of non-metals and as X [2,8,1] is a metal and Y is a non-metal [2,8,7]. Hence, electrons are not shared between 'X' & 'Y' during the formation of 'XY'X is a atom and has no charge, whereas X1+ is cation and has a unit positive charge.Y1- has a stable electronic configuration [i.e., 2,8,8] as there are 8 electrons in the valence shell.Electronic configuration of A is [2,8,8,1] and Y is [2,8,7], Hence A is a metal and Y is a non-metal. Therefore, there will be transfer of 1 valence electron from A to Y and the compound formed will be an electrovalent compound.

Chemical Bonding

Additional Questions

Questions

Unit Test Paper 4 - Chemical Bonding