Q 1 – Newlands relation is called
(a) Musical Law
(b) Law of Octaves
(c) Periodic Law
(d) Atomic Mass Law
(b) Law of Octaves
Q 2 – In Mendeleev’s Periodic Table, gaps were left for the elements to be discovered later. Which of the following elements found a place in the Periodic Table later?
(a) Chlorine
(b) Silicon
(c) Oxygen
(d) Germanium
(d) Germanium
Q 3 – The properties of eka-aluminium predicted by Mendeleev are the same as the properties of later discovered element:
(a) Scandium
(b) Germanium
(c) Gallium
(d) Aluminium
(c) Gallium
Q 4 – An atom of an element has the electronic confi-guration 2,8,2. To which group does it belong?
(a) 4th group
(b) 6th group
(c) 3rd group
(d) 2nd group
(d) 2nd group
Q 5 – The arrangement of elements in the Modem Periodic Table is based on their
(a) increasing atomic mass in the period
(b) increasing atomic number in the horizontal rows
(c) increasing atomic number in the vertical columns
(d) increasing atomic mass in the group
(b) increasing atomic number in the horizontal rows
Q 6 – Element ‘X’ forms a chloride with the formula XCl2, which is a solid with high melting point. X would most likely be in the same group of the periodic table as:
(a) Si
(b) Mg
(c) Al
(d) Na
(b) Mg
Q 7 – Carbon belongs to the second period and Group 14. Silicon belongs to the third period and Group 14. If atomic number of carbon is 6, the atomic number of silicon is
(a) 7
(b) 14
(c) 24
(d) 16
(b) 14
Q 8 – What is the atomic number of element of period 3 and group 17 of the Periodic Table?
(a) 10
(b) 4
(c) 17
(d) 21
(c) 17
Q 9 – Which one of the following statements is not correct about the trends in the properties of the elements of a period on going from left to right?
(a) The oxides become more acidic
(b) The elements become less metallic
(c) There is an increase in the number of valence electrons
(d) The atoms lose their electrons more easily
(d) The atoms lose their electrons more easily
Q 10 – A metal ‘M’ is in the first group of the Periodic Table. What will be the formula of its oxide?
(a) MO
(b) M2O
(C) M2O3
(d) MO2
(b) M2O
Q 11 – An element has atomic number 17. To which group and period does it belong to?
X(17): 2,8,7 is the electronic configuration. It has 7 valence electrons. It belongs to 17th group and 3rd period.
Q 12 – Find the atomic number of the element whose electronic configuration is 2, 8, 5.
Atomic number = 2 + 8 + 5 = 15.
Q 13 – An element A has atomic number 16. To which group and period does it belong to?
A(16) has electronic configuration: 2, 8, 6. It has 6 valence electrons and three shells. It belong to Group 16, 3rd period.
Q 14 – Write the atomic numbers of two elements X and Y having electronic configurations 2, 8, 2 and 2, 8, 6, respectively.
X = 2 + 8 + 2 = 12
Y = 2 + 8 + 6 = 16
Q 15 – What would be the nature of oxides formed by the elements on the right side of periodic table?
On right hand side of the periodic table, most of them are non-metals, therefore they form acidic oxides.
Q 16 – Calcium is an element with atomic number 20.
- Will it be a metal/non-metal?
- What will be its valency?
- What would be the formula of its chloride?
- Will it be smaller / larger than K?
Ca(20): 2, 8, 8, 2
- It will be a metal.
- Its valency is equal to 2.
- CaCl2 is the formula of its chloride.
- It will be smaller than K.
Q 17 – List the anomalies of Mendeleev’s periodic table which were removed in Modem Periodic Table.
. Co with higher atomic mass proceeds Ni with lower atomic mass. It was solved because Co has lower atomic number than Ni.
Isotopes should have been given different slots due to different atomic mass, but it is not possible due to same chemical properties. The problem was solved because isotopes have same atomic numbers.
Q 18 – How can the valency of an element be determined if its electronic configuration is known? What will be valency of an element with atomic number 9?
Valency = Number of valence electrons in case of metals and metalloids. It is also equal to 8 — Number of valence electrons in case of non-metals. F(9) has electronic configuration of 2, 7. It is a nonmetal. Its valency is equal to 1.
Q 19 – What is meant by periodicity of properties of elements? Why are the properties of elements placed on the same group of the periodic table similar?
The repetition of similar properties after a definite interval is called periodicity of properties. It is due to the same number of valence electrons.
Q 20 – Two elements M and N belong to group 1 and 2 respectively and are in the same period of the periodic table. How do the following properties of M and N vary?
- Sizes of their atoms.
- Their metallic character.
- Their valencies in forming oxides.
- Formulae of their chlorides.
- M has bigger size than N.
- M has more metallic character than N.
- M has valency equal to 1, N has valency equal to 2.
- MCl and MCl2 are formula of their chlorides.
Q 21 – The atomic number of these elements are given below:
Element | B | O | N | C |
Atomic radius (in Pm) | 86 | 66 | 74 | 97 |
Arrange this elements in increasing order of their atomic numbers. Give reason for your answer.
B(5), C(6), N(7), 0(8) is the increasing order of their atomic numbers.
It is because when we move along a period, atomic radii decreases due to increase in effective nuclear charge due to increase in number of protons and electrons continuously
Q 22 –Write the names given to the vertical columns and horizontal rows in the Modern Periodic Table. How does the metallic character of elements vary on moving down a vertical column? How does the size of atomic radius vary on moving from left to right in a horizontal row? Give reason in support of your answer in the above two cases.
Vertical columns are called groups. Horizontal rows are called periods. Metallic character of elements increases down the group because tendency to lose electrons increases down the group due to increase in atomic size. Atomic size goes on decreasing along the period due to increase in effective nuclear charge due to increase in number of protons and electrons.
Q 23 –a. Identify the elements among the following which will belong to the same group: H, He, Li, B, C. b. State the group number of the recognised elements. c. Name another one element belonging to the same group
- H and Li belong to the same group.
- They belong to group 1.
- Na (sodium) also belong to this group
Q 24 –Justify the following with suitable reasons: a. Cations are smaller than the corresponding atoms. b. Size of atom increases as we move down the group. c. Atomic size decreases as we move across a period.
- Cations are formed by loss of electrons, therefore effective nuclear charge increases, size of atom decreases.
- It is because number of shells goes on increasing down the group.
- It is because effective nuclear charge increases along a period.
Q 26 –Why is atomic number considered to be a more appropriate parameter than atomic mass for the classification of elements in a periodic table? How does the metallic character of elements vary as we move (a) from left to right in a period, and (b) top to bottom in a group of the modem periodic table?
It is because chemical properties depend upon the number of valence electrons which is determined with the help of atomic number.
- Metallic character decreases from left to right because atomic size decreases, tendency to lose electrons decreases,
- Metallic character increases from top to bottom in a group because atomic size increases due to which effective nuclear charge decreases.
Q 27 – How does tendency to lose electrons change in the Modern Periodic Table in (a) a group, (b) a period and why?
- In a group, tendency to lose electrons increases down the group because atomic size increases, forces of attraction between the valence electron and nucleus decreases.
- b. In a period, tendency to lose electrons decreases due to decrease in atomic size due to more effective nuclear charge.
Q 28 – Explain the basic character of oxides of elements down the group and across the period.
Basic character of oxides increases down the group because metallic character increases.
Basic character of oxides decreases along the period from left to right because non¬metallic character increases, metallic character decreases.
Q 29 – (a) How does the atomic radius change as you go :
(i) from left to right in a period?
(ii) down a group in the periodic table?
(b) Two elements X and Y have atomic numbers 12 and 16 respectively.
Write the electronic configuration for the these elements. To which period
of the Modern Periodic Table do these two elements belong? What type of bond will be formed between them and why?
a) i) Atomic radius decreases.
ii) Atomic radius increases.
b) Atomic number of element X-12
Electronic configuration=2,8,2
K L M
Atomic number of element =Y=16
Electronic configuration =2,8,6
K L M
The period number of an element is equal to the number of electron shells in its atom.These two elements have 3 electron have 3 electron shells,therefore they belong to 3rd period.
They will form ionic bond because X is a metal and Y is non-metal.X loses two electrons which will be gained by Y
Q 30 – (a) How would the tendency to lose electrons change as you go :
(i) from left to right across a period?
(ii) down a group?
(b) An element X (2, 8, 2) combines separately with , and radicals. Write the formulae of the three compounds so formed. To which group of the periodic table does the element ‘X’ belong? Will it form covalent or ionic compound? Why?
Q 31 – The atomic number of nitrogen, oxygen and fluorine are 7, 8 and 9 respectively. Write the electronic configuration of each element and answer the following questions:
(a) Which one of N, O and F is most electronegative and which on is least electronegative?
(b) What is the number of valence elecrtons of F?
(c) What is valency of each one of N, O and F?
Q 32 – Two elements ‘P’ and ‘Q’ belong to the same period of the Modern Periodic Table and are in Group-1 and Group-2 respectively. Compare their following characteristics in tabular form:
(a) The number of electrons in their atoms
(b) The sizes of their atoms
(c) Their metallic characters
(d) Their tendencies to lose electrons
(e) The formula of their oxides (f) The formula of their chlorides
| Group 1 | Group 2 |
| a) One electron in the valence shell | Two electrons in the valence shell |
| b) Larger atomic size compared to Group 2 | Smaller atomic size compared to Group 1 |
| c) More metallic in nature | Comparatively less metallic |
| d) Highly electropositive, readily loses electron | Comparatively less electropositive |
| e) Oxide formula: | Oxide formula: |
| f) Chloride formula: | Chloride formula: |
Q 33 – The elements Be, Mg and Ca, each having two valence electrons in their valence shells are in periods 2, 3 and 4 respectively of the Modern Periodic Table. Answer the following questions associated with these elements, giving reason in each case :
(a) In which group should they be?
(b) Which one of them is least reactive?
(c) Which one of them has the largest atomic size?
(i) All these elements belong to the 2nd group as all have two electrons in their outermost shell.
(ii) Be is the least reactive metal because reactivity of metals increases in a period as the tendency to lose electrons in a group increases. Therefore Be being the smallest in all the given elements of a period has its valence electrons nearest to the nucleus. So the removal of electrons from its valence shell will be difficult.
(iii) Ca has the largest atomic radius because it has maximum number of shells, i.e., 4.
Q 34 –Define atomic radius? Why does atomic radius decrease across a period?
Q 35 –What is the Newlands’ Law of Octaves.
According to Newlands’ law of octaves, when elements are arranged in increasing order of their atomic masses, the properties of the eighth element are a repetition of the properties of the first element. Newlands divided the elements into horizontal rows. Each horizontal row had 7 elements.
For example, let us take a row from Newlands’ classification of elements. If we take the elements Li, Be, B, C, N, O, F and Na, lithium (Li) is the first element, and sodium, the eighth. It has been found that the properties of sodium are a repetition of the properties of lithium. In short, both lithium and sodium have similar chemical properties.
Q 36 –
How does metallic character change when we move-(i) across a period from left to right, (ii) down a group?
i) As we go from left to right in a period the metallic character decreases. We know that the metal has a tendency to lose electrons. Elements on the left have 1,2,3 electrons in their outermost shell which goes on increasing as we move towards the right. It is easy to lose 1,2,3 electrons so the elements on the left are metals and going further metallic character decreases.
Q 37 – Which group of elements could be placed in Mendeleev’s Periodic Table without disturbing the original order? Give reason.
Noble gases
- Noble gases (group-) can be placed in Mendeleev’s Periodic Table without disturbing the original order.
- They are chemically unreactive.
- They got a place in the periodic table in the form of a separate group.
- They are stable in nature.
- Hence, they don’t disturb the order of Mendeleev’s Periodic Table.