Periodic Classification of Elements
Multiple Choice Questions
1. Upto which element, the Law of Octaves was found to be applicable
(a) Oxygen
(b) Calcium
(c) Cobalt
(d) Potassium
Answer (b) Calcium Explanation Newland’s law of octaves was applicable to the elements with atomic mass up to 40 da which comes up to Calcium. After calcium every eighth element possess properties similar to that of the first.Show Answer
(a) increasing atomic number
(b) decreasing atomic number
(c) increasing atomic masses
(d) decreasing atomic masses
Answer (c) increasing atomic masses ExplanationShow Answer
(a) Germanium
(b) Chlorine
(c) Oxygen
(d) Silicon
Answer (a) Germanium Explanation Mendeleev name unnamed elements as EKA- Boron EKA- Aluminium and EKA Silicon which were later replaced as Scandium, Gallium, and germanium respectively.Show Answer
following statement (s)
about the Modern Periodic Table are incorrect
(i) The elements in the Modern Periodic Table are arranged on the basis of their decreasing atomic number
(ii) The elements in the Modern Periodic Table are arranged on the basis of their increasing atomic masses
(iii) Isotopes are placed in adjoining group (s) in the Periodic Table
(iv) The elements in the Modern Periodic Table are arranged on the basis of their increasing atomic number
(a) (i) only
(b) (i), (ii) and (iii)
(c) (i), (ii) and (iv)
(d) (iv) only
Answer (b) (i), (ii) and (iii) Explanation Elements in the Modern Periodic Table are arranged on the basis of their increasing atomic number hence option i) is wrong . In modern periodic table atomic mass is not a criteria hence option ii) is wrong. Isotopes are given the same position in periodic table hence option iii) is wrong.Show Answer
(a) It has 18 horizontal rows known as Periods
(b) It has 7 vertical columns known as Periods
(c) It has 18 vertical columns known as Groups
(d) It has 7 horizontal rows known as Groups
Answer (c) It has 18 vertical columns known as Groups Explanation Modern periodic table have 18 groups and 7 periods. Columns are called groups and rows are called priods.Show Answer
(a) A, B, C
(b) B, C, D
(c) A, D, E
(d) B, D, E
Answer (b) B, C, D Explanation Element with atomic number belong to first period and element B, C and D belongs to second period.Show Answer
(a) A and $B$
(b) B and D
(c) A and C
(d) D and E
Answer (c) A and C Explanation $A$ and $C$ are fluorine and chlorine belongs to the same group.Show Answer
(a) Group 8
(b) Group 2
(c) Group 18
(d) Group 10
Answer Ans is (c) Group 18 Explanation Group 18 has its outermost shells completely filled hence element with electronic configuration belongs to group 18.Show Answer
(a) group 1
(b) group 14
(c) group 15
(d) group 16
Answer b) group 14 Explanation Carbon is an essential constituent of all organic compounds which belongs to group 14.Show Answer
(a) K shell
(b) L shell
(c) M shell
(d) $N$ shell
Answer (b) L shell Explanation In period 18 there are two shells $K$ and $L$Show Answer
(a) $Na$
(b) Al
(c) $Si$
(d) ${P}$
Answer (d) $P$ Explanation Electronic configuration of $Na, Al, Si$ and $P$ are 2,8 1, 2,8,3,2,8,4, and 2,8,5 respectively. Valence electrons in $Na$, $Al, Si$ and $P$ are 1,3,4 and 5 Hence phosphorus has maximum number of valence electrons.Show Answer
(a) O, F, N
(b) N, F, O
(c) O, N, F
(d) F, O, N
Answer (d) F, O, N Explanation Atomic radius increase as move from left to right across a period. (N7), $O(8)$ and $F(10)$ are in increasing order of atomic numbers.Show Answer
(a) $Na$
(b) ${M g}$
(c) $K$
(d) ${C a}$
Answer (c) $K$ Explanation $K$ has largest atomic radii because atomic radii decreases from left to right along a period. This is because of increase in nuclear charge which tends to pull the electron closer to the nucleus and reduces the size of the atom. Hence $K$ has the largest atomic radii.Show Answer
(a) $Mg$
(b) $Na$
(c) $K$
(d) ${C a}$
Answer (b) Na Explanation Na and $K$ belongs to the same group I and Magnesium and Calcium belongs to group ii. Sodium has 1 electron in its valence shell which can be lost easily.Show Answer
(a) $Na$
(b) ${F}$
(c) $Mg$
(d) $Al$
Answer Sodium has 1, magnesium has 2 and Aluminium has 3 electron in its outermost shell whereas Fluorine has 7 electron in its outermost shell hence Fluorine does not lose electron easily.Show Answer
(i) Isotopes of an element have same atomic masses
(ii) Isotopes of an element have same atomic number
(iii) Isotopes of an element show same physical properties
(iv) Isotopes of an element show same chemical properties (a) (i), (iii) and (iv)
(b) (ii), (iii) and (iv)
(c) (ii) and (iii)
(d) (ii) and (iv)
Answer (d) (ii) and (iv) Explanation Elements with same atomic number but different atomic masses are known as isotopes. Isotopes same chemical properties but differ in their physical properties.Show Answer
(b) $Na>Mg>Al>Si>Cl$
(c) $Na>Al>Mg>Cl>Si$
(d) $Al>Na>Si>Ca>Mg$
Answer (b) ${N a}>{M g}>Al>Si>{C l}$ Explanation Na has 1, magnesium has 2 , aluminium has 3 and Chlorine has 7 electrons in its valence shells. Hence Sodium shows maximum metallic characters followed by Magnessium, aluminium and chlorine shows non-metallic properties.Show Answer
(b) ${L i}<$ Be $<$ C $<$ O $<$ F
(c) $F<$ O $<$ C $<$ Be $<$ Li
(d) F $<$ O $<$ Be $<$ C $<$ Li
Answer $Li$ is on the left of in the $2^{\text{nd }}$ period of modern periodic table followed by berrylium. Fluorine is at right next to Neon. Hence Fluorine shows maximum non-metallic characters followed by Oxygen, Berrylium, carbon and Lithium.Show Answer
(a) $EO _3$
(b) $E _3 O _2$
(c) $E _2 O _3$
(d) $EO$
Answer (c) $E _2 O _3$Show Answer
(a) metals
(b) non-metals
(c) metalloids
(d) metal, non-metal and metalloid respectively
Answer (c) metalloidsShow Answer
(a) An element with atomic number 7
(b) An element with atomic number 3
(c) An element with atomic number 12
(d) An element with atomic number 19
Answer (a) An element with atomic number 7 Explanation Element with atomic number 7 has electron configuration 2,5 which means it can gain 3 electrons and is a electronegative element. It should be a non-metal and non-metals will form acidic oxide.Show Answer
(a) Metal
(b) Metalloid
(c) Non-metal
(d) Left-hand side element
Answer (b) Metalloid Explanation Element with atomic no. 14 is Silicon and is a metalloid. It forms acidic oxide , thus behaving as a nonmetal and also forms covalent halide, thus acting as a metal.Show Answer
Options
(a) (i) and (ii)
(b) (ii) and (iii)
(c) (iii) and (iv)
(d) (i) and (iv)
Answer (b) (ii) and (iii) Explanation Atomic radius is the distance between the nucleus and outermost orbital is shown clearly in images ii) and iii) where as in image i) and iv) it is not depicted.Show Answer
(a) Atomic radius
(b) Metallic character
(c) Valence
(d) Number of shells in an element
Answer (c) Valence Explanation Valency remain same in a group.Show Answer
(a) increases
(b) decreases
(c) does not change appreciably
(d) first decreases and then increases
Answer (b) decreases Explanation Atomic radius decreases when we move from left to right in a periods hence the size of the atom also decreases.Show Answer
(a) Be Mg Ca
(b) Na Li K
(c) $Mg Al Si$
(d) $CO O N$
Show Answer
Answer
(a) Be Mg Ca
Explanation
Metallic character increase as we move down the group. In the elements that belong to same group Berrylium is at the top and Calcium is at the bottom.
Short Answer Questions
27. The three elements $A, B$ and $C$ with similar properties have atomic masses $X, Y$ and $Z$ respectively. The mass of $Y$ is approximately equal to the average mass of $X$ and $Z$. What is such an arrangement of elements called as? Give one example of such a set of elements.
Answer Such an arrangement of elements are called Triads. Ex: Lithium Sodium and Potassium make a triad. Their atomic masses are 6.9, 23.0 and 39.0 respectively. An average mass of $Li$ and $K$ is approximately equal to the atomic mass of Na.Show Answer
Answer
a) $Na, Mg, Al$ and $K$ are metals. $F$ and $Cl$ are Halogens. These make two sets of elements b) Given set represent Mendeleev’s law of periodicity.Show Answer
(a) $Na, Si, Cl$
(b) Be, Mg, Ca
Atomic mass of $ Be \quad {9;} Na \quad{23;} Mg \quad{24;} Si \quad{28;} Cl \quad{35;} Ca \quad 40 $ Explain by giving reason.
Answer Though atomic mass of Silicon is the average of atomic masses of Sodium and Chlorine they do not have similar properties hence they cannot be classified as Dobereiner’s triadShow Answer
Answer In Mendeleev ’s Periodic Table there are instances where elements with higher atomic mass is placed before the element with lower atomic mass. This was done to ensure that elements with similar properties were included in the same group. Hence Cobalt was placed before Nickel despite of higher atomic number of Cobalt than Nickel.Show Answer
Answer Hydrogen occupies a unique position in Modern Periodic Table because of the following reasons. 1 Hydrogen and alkali metals have similar outer electronic configuration as both have one electron in their outermost shell. 2 Properties of Hydrogen are similar to properties of Halgens as electronic configurations of halogens and Hydrogen are same.Show Answer
Answer Chlorides of Eka-silicon: $ECl _4$ Chlorides of Eka-Aluminium:$ECl _3$Show Answer
Answer A Belongs to Group 13, A Belongs to Group 14 and C Belongs to Group 2. Valency of A is3, B is 4 and C is 2.Show Answer
Answer If an element $X$ is placed in group 14 it has 4 electron in its outermost orbit. Formula of its Chloride is $ECl_4$. Here element can form compound by sharing electrons hence it will be a chemical bonding.Show Answer
(a) $X$ has 12 protons and 12 electrons
(b) $Y$ has 12 protons and 10 electrons
Answer From electron arrangement $X-2.8 .2$ $Y-2.8$ Since $Y$ has fewer energy levels it’s atomic radius will be smaller than that of $X$.Show Answer
(a) Li, Be, F, N
(b) Cl, At, Br I
Answer Given elements are in the same group and are arranged from left to right. So Increasing order of their atomic radiiis a) $Li>Be>F>N$ b) $Cl>Br>I>At$Show Answer
(a) 2, 8, 2
(b) 2, 8, 1
(c) 2, 8, 7
(d) 2, 1
Answer a) Magnesium b) Sodium c) Chlorine d) LithiumShow Answer
Answer Element A is K (Potassium). The electronic configuration of element A (atomic number 19) would be 2, 8, 8, 1. As it has only one valence electron therefore it must be a metal. Thus it is potassium. Element B is Cl (Chlorine). The electronic configuration of element B (atomic number 17) would be 2, 8, 7. As it has 7 valence electrons therefore it must be a non-metal. Thus it is chlorine. A metal and a non-metal usually combine with an ionic bond. Metals have tendency to lose electrons and form cations whereas non-metals can accept electrons to form anions. AB Potassium and chlorine will combine with an ionic bond to form potassium chloride ( $KCl)$. The electron dot structure of $KCl$ is as given below:Show Answer
Answer $Ge>Ga>Mg>Ca>K$Show Answer
(a) An element which is a soft and reactive metal
(b) The metal which is an important constituent of limestone
(c) The metal which exists in liquid state at room temperature
Answer a) Sodium b) Calcium c) MercuryShow Answer
(a) A soft metal stored under kerosene
(b) An element with variable (more than one) valency stored under water.
(c) An element which is tetravalent and forms the basis of organic chemistry
(d) An element which is an inert gas with atomic number 2
(e) An element whose thin oxide layer is used to make other elements corrosion resistant by the process of " anodising"
Show Answer
Answer
a) Sodium Group 1 Period 3
b) Phosphorus Group 15 Period 3
c) Carbon Group 14 Period 2
d) Helium Group 18 Period 1
e) Aluminium Group 13 Period 3
Long Answer Questions
42. An element is placed in 2nd Group and 3rd Period of the Periodic Table, burns in presence of oxygen to form a basic oxide.
(a) Identify the element
(b) Write the electronic configuration
(c) Write the balanced equation when it burns in the presence of air
(d) Write a balanced equation when this oxide is dissolved in water
(e) Draw the electron dot structure for the formation of this oxide
Answer a) Element is Magnessium b) Electronic Configuration-2,8,2 c) $2 Mg+O^{2} \longrightarrow 2 MgO$ d) $MgO+H_2 O \longrightarrow Mg(OH)_2$Show Answer
(a) Where in the periodic table are elements $X$ and $Y$ placed?
(b) Classify $X$ and $Y$ as metal (s), non-metal (s) or metalloid (s)
(c) What will be the nature of oxide of element Y? Identify the nature of bonding in the compound formed
(d) Draw the electron dot structure of the divalent halide
Answer
a) $X$ is in Group 17, period 3 and $Y$ is in group 2 Period 4.
b) $X$ is Non-metal and $Y$ is metal c) Y Oxide will be basic in nature. Compound formed by ionic bond.
d) Electron dot structure for calcium chlorideShow Answer
(a) Identify the elements
(b) Identify the Group number of these elements in the Periodic Table
(c) Identify the Periods of these elements in the Periodic Table
(d) What would be the electronic configuration for each of these elements?
(e) Determine the valency of these elements
Answer a) Elements are Neon (10) Calcium (20) Nitrogen (7) Silicon (14) b) Neon belongs to group 18, Calcium belongs to group 2, Nitrogen belongs to group 7 and Silicon belongs to group 14. c) Nitrogen and Neon belong to period 2. Calcium and silicon belongs to Period 3. d) Electronic Configurations Neon-2,8 Calcium-2,8,8,2 Nitogen-2,5 Silicon-2,8,4 e) Valency Neon-0 Calcium-2 Nitogen-3 Silicon-4Show Answer
$ \begin{array}{|c|c|c|c|c|c|c|c|c|c|c|c|} \hline & 1 & 7 & & & & 2 & & & & & \\ \hline & & & & & & & & & & & \\ \hline & & 3 & 8 & & & & 9 & & 5 & & \\ \hline & & & & & & 4 & & & & 6 & \\ \hline & & & & & & & & & & & \\ \hline & & & & & & & & & & & \\ \hline & & & & & & & & & & & \\ \hline & & & & & & & & & & & \\ \hline & & & & & & & & & & & \\ \hline \end{array} $
Fig. 5.1
Across:
(1) An element with atomic number 12.
(3) Metal used in making cans and member of Group 14.
(4) A lustrous non-metal which has 7 electrons in its outermost shell.
Down:
(2) Highly reactive and soft metal which imparts yellow colour when subjected to flame and is kept in kerosene.
(5) The first element of second Period
(6) An element which is used in making fluorescent bulbs and is second member of Group 18 in the Modern Periodic Table
(7) A radioactive element which is the last member of halogen family.
(8) Metal which is an important constituent of steel and forms rust when exposed to moist air.
(9) The first metalloid in Modern Periodic Table whose fibres are used in making bullet-proof vests
Answer Across DownShow Answer
(b) Arrange them in the order of their group also.
Answer a) H, He, Li, Be, B, C, N, O, F, Ne, Mg, Al Si,P, S, Cl, Ar, K, Ca b) Group 1:H, Li, Na, K Group 2: Be, Mg,Ca Group 13: B. Al Group 14: C, Si Group 15: N. P Group 16: 0, S Group 17: F. U Group 18: He, Ne, ArShow Answer
(a) Name the elements which have taken the place of these elements
(b) Mention the group and the period of these elements in the Modern Periodic Table.
(c) Classify these elements as metals, non-metals or metalloids
(d) How many valence electrons are present in each one of them?
Answer a) Eka-Silicon was replaced by germanium, Eka-aluminium was replaced by Gallium b) Germanium-Group 14 Period 5 Gallium-Group 13 Period 5 c) Germanium is a metalloid and Gallium is a metal. d) Germanium has 4 electron, Gallium has 3 valence electronsShow Answer
(b) Electronegativity of the element decreases down the group and increases across the period
(c) Atomic size increases down the group and decreases across a period (left to right)
(d) Metallic character increases down the group and decreases across a period.
On the basis of the above trends of the Periodic Table, answer the following about the elements with atomic numbers 3 to 9 .
(a) Name the most electropositive element among them
(b) Name the most electronegative element
(c) Name the element with smallest atomic size
(d) Name the element which is a metalloid
(e) Name the element which shows maximum valency.
Answer (a)Electropositive nature of the element(s) increases down the group and decreases across the period. (b) Electronegativity of the element decreases down the group and increases across the period (c) Atomic size increases down the group and decreases across a period (left to right) (d) Metallic character increases down the group and decreases across a period. a) Lithium is the most electropositive element . b) Fluorine is the most electronegative element c) ) Fluorine is the element with smallest atomic size among the given elements c) Boron d) Carbon is the element which shows maximum valency.Show Answer
(a) Identify the element $X$
(b) Write the electronic configuration of $X$
(c) Write the balanced chemical equation for the thermal decomposition of ferrous sulphate crystals?
(d) What would be the nature (acidic/ basic) of oxides formed?
(e) Locate the position of the element in the Modern Periodic Table
Answer a) Element $X$ is Sulphur b) 2,8,6 c) $2 FeSO_4 \longrightarrow Fe_2 O_3+SO_2+SO_3$ d) Sulphur oxides are acidic in nature e) Group 16 Period 3Show Answer
(a) Identify the element $X$. How many valence electrons does it have?
(b) Draw the electron dot structure of the diatomic molecule of $X$. What type of bond is formed in it?
(c) Draw the electron dot structure for ammonia and what type of bond is formed in it?
Answer (a) Answer is Nitrogen and it has 5 electrons in its outermost shell. (b) Triple covalent bonds (c)
Ammonia forms covalent bonding 3 single covalent bondShow Answer
Answer Inert gases could be placed in Mendeleev’s Periodic Table without disturbing the original order. Before Mendeleev Noble gases; like Helium. Neon and Argon had been mentioned by various scientists. But these gases could be grouped together as noble gases much later than Mendeleev’s discovery. Mendeleev used 63 elements till his periodic table because these were the only known elements till his time. However, he was bold enough to leave gaps in his periodic table. He had predicted that that more elements would be discovered in times to come. Mendeleev’s Periodic Table was the first comprehensive attempt to classify elements on the basis of their chemical properties. This is the main reason that new elements could be easily placed in Mendeleev’s Periodic Table without disturbing the original order.Show Answer
Show Answer
Answer
During Mendeleev’s time, only 63 elements were known. Mendeleev examined the correlation between chemical properties and Atomic manes of elements. For this, he concentrated on compounds which were formed by the elements with hydrogen and oxygen. He selected hydrogen and oxygen, because these elements make compound with most of the other elements.
Mendeleev made 63 cards and wrote the name of an element on each card: along with the chemical properties of a particular element. Then, he pinned those cards on a wall. He could observe that most of the elements could be arranged in periodic table in increasing order of their atomic masses. That is how Mendeleev arrived at “Periodic law”. Mendeleev’s Periodic Law states that properties of elements are periodic function of their atomic masses.
