Selina Concise Class 10 Chemistry Solution Chapter No. 1- ‘Periodic Table, Periodic Properties and Variations of Properties’ For ICSE Board Students
1.) What is the significance of atomic number in the modern periodic table ?
Answer-the significance of atomic number in the modern periodic table is ,
i) In a Periodic Table the chemical and physical properties of the element in modern periodic table is the periodic function of their atomic number.
ii) In everyday table, atomic number is determined the position of the elements.
2.) Arrange the following as per instructions given in the brackets.
(a) Mg, Cl, Na, S, Si (decreasing order of atomic size)
Answer-decreasing order is,
Na > Mg > Si > S > Cl
186 pm > 160 pm > 117 pm > 104 pm
(b) Cs, Na, Li, K, Rb (increasing metallic character)
Answer- increasing order is,
Li < Na < K < Rb < Cs
c) Na, K, Cl, S, Si (increasing ionisation potential)
Answer- increasing ionisation potential is,
Cl < S < Si < Na < K
(d) Cl, F, Br, I (increasing electron affinity)
Answer-Increasing electron affinity is,
I < Br < F < Cl
-295 KJ mol^-1<-324KJ mol^-1<-327.9 KJ mol^-1<-349 KJ mol^-1
(e) Cs, Na, Li, K, Rb (decreasing electronegativity)
Answer- Li > Na > K-Rb> Cs
the electronegativity arranged in decreasing order: 1.0 >0.9 >0.8= 0.8 >0.7
(f) K. Pb, Ca, Zn (increasing reactivity)
Answer- increasing reactivity is
Pb>Zn>Ca>K
(g) Li, K, Na, H (decreasing order of their potential ionisation)
Answer- decreasing order of their potential ionisation is
H > Li > Na > K
3] Chlorine in the Periodic Table is surrounded by the elements with atomic number 9, 16, 18 and 35.
(a) Which of these have Physical and Chemical properties Resembling chlorine?
Answer- the elements with atomic number 9 and 35.
(b) Which is more electronegative than chlorine ?
Answer- an atomic number 9 is more electronegative than chlorine.
4] First ionisation enthalpy of two elements X and Y are 500 kJ mol^-1 and 375 kJ mol ^-1 respectively. Comment about their relative position in a group as well as in a period.
Answer- if the ionisation is more it will be situated more at the top of group as going down the group size increases and ionisation enthalpy decreases. Whereas when moving in a period the ionization enthalpy increases as the size of atom goes on decreasing…. Therefore the element with higher enthalpy will be placed more on the right than the element with lower enthalpy.
5] Arrange the following in order of increasing radii : (a) Cl-, Cl (b) Mg+2, Mg, Mg+ (c) N, O, P
Answer- the order of increasing radii is,
a) Cl > Cl-
b) Mg + 2 > Mg + > Mg
c) O > N > P
6]Which element from the following has the highest ionisation energy? Explain your choice.
a) P, Na, Cl
(b) F, O, Ne
(c) Ne, He, Ar
Answer- a)P,Na, Cl
Cl – Cl is a non-metal non-metal. It as the high ionisation energy, when it compared to the metals. It is belongs to the third period(group 17).
b) F, O, Ne
Ne – Ne is a inert gas. There is stable electronic configuration . Hence the inert gases have zero electron affinity.
c) Ne, He, Ar
He – He is a inert gas. The atomic size increase then the ionisation energy decrease.
7) The electronegativitie (according to Pauling) of the elements in Period 3 of the Periodic Table are as follows with the elements arranged in alphabetical order:
Al CI Mg Na P S Si |
1-5 3-0 1-2 0.9 2.1 2-5 1-8 |
Arrange the elements in the order in which they occur in the Periodic Table from left to right. (The group 1 element first, followed by the group 2 element and so on, up to group 7).
Answer- the elements in the order in which they occur in the periodic table from left to right.
The order is – Na Mg Al Si P S Cl.
8] Choose the word or phrase from the brackets which correctly completes each of the following statements :
a) The element below sodium in the same group would Be expected to have….(lower/higher) Electro-negativity than sodium and the element Above chlorine would be expected to have a……..(lower/higher) ionization potential than chlorine.
Answer- a)The element below sodium in the same group would Be expected to have lower Electro-negativity than sodium and the element Above chlorine would be expected to have a higher ionization potential than chlorine.
(b) On moving from left to right in a given period, the number of shells ———… (remains the same/increases decreases).
Answer-(b) On moving from left to right in a given period, the number of shells remains the same.
(c) On moving down a group, the number of valence electrons…………. (remains the same/increases/decreases).
Answer-(c) On moving down a group, the number of valence electrons remains the same.
(d) Metals are good ………..……….……….. dising agents/reducing agents) because they are electron (acceptors/donors).
Answer- (d) Metals are good reducing agents because they are electron donors.
10) Parts (a) to (e) refer to change in the properties of elements on moving from left to right across a period of the periodic table. For each property, choose the correct answer.
a) The non-metallic character of the elements:
1.) Decreases
2) Increases
3.) Remains the same
4.) Depends on the period
b) The electronegativity:
(1) Depends on the number of valence electrons
(2) Remains the same
(3) Decreases
(4) Increases
c) The ionization potential:
1) goes up and down
2) Decreases
3) Increases
4) Remains the same
d) The atomic size:
(1) Decreases
(2) Increases
(3) Remains the same
(4) Sometimes increases and sometimes decreases
(e) The electron affinity of elements in group 1 to 7:
(1) Goes up and then down
(2) Decreases and then increases
(3) Increases
(4) Decreases
Answer-
(1) The non-metallic character increases from left to right across a period
(2) The electronegativity of elements increases from left to right across a period
(3) The ionisation potential of elements increases from left to right across a period
(4) The atomic size of elements decreases from left to right across a period
(5) The electron affinity of the elements in groups 1 to 7 increases
11.) The elements of one short period of the periodic table are given below in order from left to right:
Li Be B COF Ne
(a) To which period do these elements belong?
(b) One element of this period is missing. Which is the missing element and where should it be placed?
(c) Place the three elements: Fluorine, Beryllium and nitrogen in the order of increasing electronegativity.
(d) Which one of the above element belongs to the halogen series?
Answers –
a) The elements belongs to the 2nd period.
b) the nitrogen element should be placed between carbon and oxygen.
c) the increasing order of electronegativity is Be < N < F.
d) Fluorine element belongs to the halogen family.
12) Select the correct answer from the choices A, B, C, D which are given. Write down only the letter corresponding to correct answer. With reference to the variation of properties in the Periodic table, which of the following isgenerally true?
(a) Atomic size increases from left to right across a period.
(b) Ionization potential increases from left to right across a period.
(c) Electron affinity increases going down a group.
(d) Electro-negativity Increases going down a group.
Answer :
(b) Ionization potential increases from left to right across a period.
2009
(a) Among Period 2 elements A, B, C and D, the one which has high electron affinity is
A.) Lithium
B.) Fluorine
C) Carbon
D.) Neon
Answers –
A) Lithium is the right option
The electron affinity decreases from left to right in a period as the non-metallic character increases.
(b) Select from the table:
(1) Which is the most electronegative?
(2) How many valence electrons are present in G?
(3) Write the formula of the compound between B and H.
(4) In the compound between F and J, what type of bond will be formed?
(5) raw the electron dot structure for the compound formed between C and K.
Answer :
(1)The most electronegative element of the table is J.
(2) The number of valence electrons present in G are 5.
(3) the formula of the compound between B and H will be B₂H
(iv) In the compound between F and J, the type of bond formed will be covalent.
(v) The electron dot structure for the compound formed between C and K is
2010
(a) The number of electrons in the valence shell of a halogen is….. A-1, B-3, C-5, D-7.
(b) Electronegativity across the period [Increases/decreases].
(c) Non-metallic character down the group………[increases/decreases].
(d) Atomic number of an element is 16. State
(1) It belongs to period 3
(2) the number of valence electrons in the element
(3) is the element metal or non-metal
Answer –
(a) The number of electrons in the valence shell of a halogen is
(b) Electronegativity across the period increases.
(c) Non-metallic character down the group decreases.
(d) Atomic number of an element is 16
(1) It belongs to period 3
(2) The number of valency electrons in the element is 6
(3) The element is a non-metal.
2011
(a) Give reasons – The oxidising power of elements increases from left to right along a period.
(b) Select the correct answer:
(1) Across a period, the ionisation potential …………[increases, decreases, remains same]
(2) Down the group, electron affinity……[increases, decreases, remains same]
(c) Choose the correct answer from the choice given:
(1) In the periodic table, alkali metals are placed in the group A: 1, B: 11, C: 17, D: 18.
(2) Which of the following properties do not match with elements of the halogen family?
A) They have seven electrons in their valence shell.
B) They are highly reactive chemically.
C) They are metallic in nature.
D) They are diatomic in their molecular form.
State the group and period of the element having three shells with three electrons in the valence shell.
Answer :
(a) Oxidising power means to accept electrons.The tendency to gain electrons by elements is known as oxidising power .we move from left to right along a periodic table the size of element decrease hold of nucleus increases incoming electron is accepted easily thus oxidising power of element increases.
(b) (1) Across a period, the ionisation
(2) Down the group, electron affinity decreases.
(c) (1) A: 1, In the periodic table the alkali metals are placed in Group 1.
(2) C: The halogen family, they are non – metallic in nature.
(d) in the periodic table, in third period the elements has a three shells.
2012
(a) Choose the correct answer from the option: An element in Period 3 whose electronic affinity is zero.
A) Noon B) Sulphur
C) sodium D) Argon
(b) Give reason:
(1) Ionisation potential of the element increases across a period.
(2) Alkali metals are good reducing agents.
(3) There are three elements E, F, G with atomic numbers 19, 8 and 17 respectively. Classify the above elements as metals and non-metals.
(d) Name: A metal present in Period 3, Group l of the periodic table.
Answers :
a) Argon element in period 3 whose electronic affinity is zero. as it’s a inert gas having octet configuration.
B) (1) the alkali metal elements are present in group 1.the alkali metal valency is 1.atomic radius decreases across a period. Alkali metals are good reducing agent. Due to this, attraction between the nucleus and the electron increases. Hence, it results in an increase in the ionisation potential.
(C) E is a metal, atomic number of E is 19.Electronic configuration of E = 1s22s22p6 3s2 3p6 4s¹ ,there is only 1valence electron.
F is a non-metal. Atomic number is . electronic configuration of F = 1s22s²2p¹ As the number of valence electron is 4.
G is a non metal, the atomic number is 17. Electronic configuration = 1s2 2s2 2p2 3s2 3p5, the valence electron is 5.
(d) Sodium the sodium metal is present in period 3,group l of the periodic table.
2013
(a) Among the Period 2 elements, the element which has high electron affinity is
A) Lithium
B) Carbon
C) Chlorine
D) Fluorine
Answer – D. Fluorine
(b)
Group no.
Group no | 1-1A | 2 IIA | 13-III A | 14-IVA | 15-VA | 16-VIA | 17-VllA | 18-0 |
2nd period | Li | D | O | J | Ne | |||
3rd period | A | Mg | E | Si | H | M | ||
4th period | R | I | Q | U | Y |
In the above table, H does not represent hydrogen. Some elements are given in their own symbol and position in the periodic table while others are shown with a letter. Answer the following questions.
i) Identify the most electronegative element.
Answer-I
II) Identify the most reactive element of Group I.
Answer – R
III) Identify the element from Period 3 with least atomic size.
Answer –M
IV) How many valence electrons are present in Q?
Answer – 5
v) Which element from group 2 would have the least ionisation energy?
Answer – T
vi) Identify the noble gas of the fourth period.
Answer – Y
Vii) In the compound between A and H, what type of bond would be formed and give its molecular formula.
Answer- A valency is +1 so A has 1 valency electron,
H valency is -2 so H valency has 6,
Ionic bond is formed between A and H. Molecular formula is A2H.
(C) Identify: The element which has the highest ionisation potential.
Answer :the helium element which has highest ionisation potential.
2014
(a) Choose the correct answer from the choice given:
(i) Ionisation potential increases over a period from left to right because the
A) Atomic radius and nuclear charge increase
B) Atomic radius and nuclear charge decrease
C) Atomic radius increases and nuclear charge decreases
D) Atomic radius decreases and nuclear charge increases
Answer – D. Atomic radius decreases and nuclear charge increases
ii) An element A belonging to Period 3 and Group II will have
A,) 3 shells and 2 valence electrons
B) 2 shells and 3 valence electrons
C) 3 shells and 3 valence electrons
D) 2 shells and 2 valence electrons
Answer –A. 3 shells and 2 valence electrons
(b) An atomic number of an element Z is 16. Answer the following:
Answer – Sulphur, the atomic number of sulphur is 16.
1) State the period and group to which Z belongs.
Answer –the period no 3 and group 16 of the periodic table.
2) Is Z a metal or a non-metal?
Answer –sulphur is non – metal
C) State the formula of the compound between Z and hydrogen.
Answer – the valency of sulphur is -2.
And the valency of Hydrogen is +1. So the formula between z(sulphur) and hydrogen is H2S
d) M is a metal above hydrogen in the activity series and its oxide has the formula M2O. This oxide, when dissolved in water, forms the corresponding hydroxide which is a good conductor of electricity. In the above context, answer the following:
1 )what kind of combination exists between M and O?
Answer –an ionic bond exists between M and O.
2) State the number of electrons in the outermost shell of M.
Answer – the number of electrons in the outermost shell of M is 1.
3) Name the group to which M belongs.
Answer- M belongs to the group 1 in the periodic table.
e) Give one word or phrase for: The amount of energy released when an atom in the gaseous state accepts an electron to form an anion.
Answer – the electron affinity
f)Match the option A and B with the statements (i) and (ii):
A. Metal | i) the metal that forms two types of ions. |
B. Iron | ii) An element with electronic configuration 2,8,8,3. |
Answer – A] ii)
B] i)
2015
(a) Among the elements given below, the element with the least electronegativity is
i) Lithium
ii) Carbon
iii) Boron
iv) Fluorine
Answer- i) Lithium because in the periodic table, the lithium is present on the left side. It will be the least electronegative element.
(b) The metals of Group 2 from top to bottom are Be, Mg, Ca, Sr and Ba.
(i) Which of these elements will form ions most readily and why?
Answer-the ionisation energy of elements, down the group decreases as the size increases. Hence the Ba metal will form ions.
(ii) State the common feature in the electronic configuration of all these elements.
Answer–All the elements have 2 electrons in their valence shell. Means the valency in a group remains the same.
2016
a) metal are good (acceptors/donors)……………(oxidising agents/reducing agents) because they are electron… .. … ..
Answer – metal are good reducing agent because they are electron donors.
b) An element with the atomic number 19 will most likely combine chemically with the element whose atomic number is:
1) 17
2) 11
3) 18
4) 20
Answer – 1)17
C) Rewrite the following sentences by using the correct symbol > (greater than) or < (less than) in the blanks given:
The ionization potential of potassium is………….That of sodium.
Answer – The ionization potential of potassium is less than that of sodium.
I.P of K < I. P of Na.
The electronegativity of lodine is. … .. … . . That of chlorine.
Answer – The electronegativity of lodine is less than That of chlorine.
Electronegativity I <Electronegativity Cl.
(d) Fill in the blanks by selecting the correct word from the brackets:
If an element has a low ionization energy then it is likely to be (non-metallic). (metallic
Answer – If an element has a low ionization energy then it is likely to be metallic.
ii )If an element has seven electrons in its outermost shell then it is likely to have the (largest/ smallest) atomic size among all the elements in the same period.
Answer- If an element has seven electrons in its outermost shell then it is likely to have the smallest atomic size among all the elements in the same period.
2018
(a) In Period 3 of the Periodic table, element B is placed to the left of element A. On the basis of this information, choose the correct word from the brackets to complete the following statements:
(i) The element B would have (lower /higher) metallic character than A.
Answer – (i) The element B would have higher metallic character than A.
The element A would probably have (lesser / higher) electron affinity than B. (iii) The element A would have (greater /smaller) atomic size than B.
Answer – (ii) The element A would probably have higher electron affinity than B.
(iii) The element A would have (greater /smaller) atomic size than B.
Answer – (iii) The element A would have smaller atomic size than B.