Periodic Table, Periodic Properties (PDF)

# Periodic Table, Periodic Properties and Variations of Properties ## Syllabus - Periodic properties and variations of properties - Physical and Chemical - Periodic properties and their variations in groups and periods. - Definitions and trends of the following periodic properties in groups and periods should be studied: - atomic size - ionization potential - metallic character - non-metallic character - electron affinity - electronegativity - Periodicity on the basis of atomic number for elements. - The study of modern periodic table up to period 4 (students to be exposed to the complete modern periodic table but no questions will be asked on elements beyond period 4 - Calcium). - Periodicity and other related properties to be explained on the basis of nuclear charge and shells (not orbitals). - (special reference to the alkali metals, alkaline earth metals, halogens and inert gases). - Note: According to the recommendation of International Union of Pure and Applied Chemistry (IUPAC), the groups are numbered from 1 to 18 replacing the older notation of groups IA ...... VIIA, VIII, IB ... .... VIIB and 0. However, for the examination both notations will be accepted. - Old notation IA IIA IIIB IVB VB VIB VIIB VIII ІВ ІІВ IA IVA VA VIA VIIA 0 - New notation 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 ## 1.1 Introduction - Elements are pure substances made up of one type of atoms. They are the basic units of all types of matter. - In order to study elements in an organised manner, they need to be classified. - You have studied in class IX the contributions of Döbereiner, Newlands and Mendeleev to the classification of elements. - Döbereiner grouped the elements in groups of three (triads) with similar properties such that the atomic weight of the middle element was the arithmetic mean of the other two. - Example 40 Ca, 88 Sr, 137 Ba and 35 C1, 80 Br, 127 I. - Newlands observed that when elements are arranged in increasing order of their atomic weights, every eighth element beginning from any element resembles the first element in its physical and chemical properties. - Mendeleev gave the first periodic table of elements based on his law which states that "the properties of elements are the periodic functions of their atomic masses". This arrangement enabled Mendeleev to place 63 elements known at that time in vertical columns (groups), and in horizontal rows (periods). - He predicted the existence of those elements which were yet to be discovered. - But this method could not explain the positions of certain elements, the rare earth metals and the isotopes. - These defects were removed when Henry Moseley put forward the modern periodic table, which was based on atomic number. - Atomic number is equal to the number of electrons in the energy shells of an atom. - Physical and chemical properties of an element depend on the number of electrons and their arrangement. - Hence atomic number is the fundamental property of an element. - Moseley stated that "the physical and chemical properties of elements are the periodic functions of their atomic number". - Later on Niels Bohr gave the extended form of the table known as the long form of the modern periodic table (given ahead). ## 1.2 Salient Features of the Modern Periodic Table (See Page 2) ### Groups: - The modern periodic table has eighteen vertical columns. Each vertical column accommodates elements with the same number of electrons in the outermost shell. These vertical columns are known as groups, arranged from left to right in the order of increasing atomic number. - Group 1: These elements are known as Alkali metals (except hydrogen) as they form strong alkalis with water. - Group 2: Alkaline earth metals – They form weaker alkalis as compared to group 1 elements. - Groups 3, 4, 5, 6, 7, 8, 9, 10, 11 and 12 are known as the transition elements. All the elements of these groups are metals. They have their two outermost shells incomplete. - Group 13: Boron family - Boron is the first member of the group. - Group 14: Carbon family. - Group 15: Nitrogen family. - Group 16: Oxygen family, also known as chalcogens, meaning ore forming. - Group 17: These elements form salts and so are known as Halogens (meaning – salt formers). - Note: The elements of groups 1, 2, 13, 14, 15, 16 and 17 have 1, 2, 3, 4, 5, 6 and 7 electrons in their valence shell (outermost shell) respectively. They are known as the main group elements or representative elements or normal elements. The outermost shell of all the elements of these groups are incomplete. - Group 18: (Zero group) - Elements of this group are called noble gases or inert gases. These elements have their outermost orbit complete. Due to stable electronic configuration, they hardly react with other elements. ### Periods - There are seven horizontal rows in the modern periodic table. They are known as periods (see table given below). - Each period begins with an element having one electron in its valence shell and ends with completely filled outermost orbit (valence shell). The number of shells present in an atom determines its period. For example: - Elements of period one have one shell, elements of period two have two shells, and that of period three have three shells and so on. | Period | Type of Period | No. of elements | Atomic Number | IA | IIA | IIIB | IVB | VB | VIB | VIIB | VIII | IB | IIB | IIIA | IVA | VA | VIA | VIIA | 0 | |---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---| | 1 | Shortest | 2 | 1 and 2 | H 1 | | | | | | | | | | | | | | | | He 2 | | 2 | Short | 8 | 3 to 10 | Li 3 | Be 4 | | | | | | | | | B 5 | C 6 | N 7 | O 8 | F 9 | Ne 10 | | 3 | Short | 8 | 11 to 18 | Na 11 | Mg 12 | | | | | | | | | Al 13 | Si 14 | P 15 | S 16 | Cl 17 | Ar 18 | | 4 | Long | 18 | 19 to 36 | K 19 | Ca 20 | Sc 21 | Ti 22 | V 23 | Cr 24 | Mn 25 | Fe 26 | Co 27 | Ni 28 | Cu 29 | Zn 30 | Ga 31 | Ge 32 | As 33 | Se 34 | Br 35 | Kr 36 | | 5 | Long | 18 | 37 to 54 | Rb 37 | Sr 38 | Y 39 | Zr 40 | Nb 41 | Mo 42 | Tc 43 | Ru 44 | Rh 45 | Pd 46 | Ag 47 | Cd 48 | In 49 | Sn 50 | Sb 51 | Te 52 | I 53 | Xe 54 | | 6 | Longest | 32 | 55 to 86 | Cs 55 | Ba 56 | La 57 | Hf 72 | Ta 73 | W 74 | Re 75 | Os 76 | Ir 77 | Pt 78 | Au 79 | Hg 80 | Tl 81 | Pb 82 | Bi 83 | Po 84 | At 85 | Rn 86 | | 7 | Longest | | 87 to | Fr 87 | Ra 88 | Ac 89 | Rf 104 | Db 105 | Sg 106 | Bh 107 | Hs 108 | Mt 109 | Ds 110 | Rg 111 | Cn 112 | Nh 113 | Fl 114 | Mc 115 | Lv 116 | Ts 117 | Og 118 | - Group 1 are Alkali metals (except hydrogen) - Group 2 - Alkaline earth metals - Group 3 to 12 - Transition elements - Group 17 Halogens - Group 18 Inert gases - Group IIIB 6th period - Lanthanides (Rare earth elements) - Group IIIB 7th period - Actinides (Radioactive elements) ## 1.3 Periodicity - The properties that reappear at regular intervals, or in which there is gradual variation (i.e. increase or decrease) at regular intervals, are called 'periodic properties' and the phenomenon is known as the periodicity of elements. - Cause of periodicity - The cause of periodicity is the recurrence of similar electronic configuration i.e. having the same number of electrons in the outermost orbit. - In a particular group, electrons in the outermost orbit remain the same i.e. electronic configuration is similar. Since chemical properties of elements depend upon the number of electrons in their outermost shell, thus elements of the same group have similar properties. ## 1.4 Shells (Orbits) and Valency - Orbits: Electrons revolve around the nucleus in certain definite circular paths called orbits or shells. - (1) Number of shells : - (a) Down a group, i.e., from top to bottom. The number of shells increases successively, i.e., one by one, such that the number of shells that an element has, equals the number of the period to which that element belongs. - (b) Across a period, i.e., from left to right. On moving from left to right in a given period, the number of shells remains the same. For example, in the 2nd period, the number of shells remains two, i.e., equal to the number of the period. Similarly in the third period the number of shells remains three and so on. - (2) Valency - Valency denotes the combining capacity of the atom of an element. It is equal to the number of electrons an atom can donate or accept or share. - On moving down a given group, the number of electrons in the outermost shell, i.e., valence electron, remains the same. Therefore, valency, in a group, also remains the same. - In a given period, the number of electrons in the valence (outermost) shell increases from left to right. But the valency increases only upto Group 14, where it becomes 4, and then it decreases, i.e., in Group 17 it becomes 1. - Note 1: Valency depends on the number of electrons in the outermost shell (i.e. valence shell). If the number of electrons present in the outermost shell are 1, 2, 3 or 4, then their valency is 1, 2, 3 or 4 respectively. - If the number of electrons present in the outermost shell are 5, 6 or 7, then their valency is 8 – 5 = 3, 8 – 6 = 2 and 8 – 7 = 1 respectively. - Note 2: Valency is the combining capacity so it is always positive. ## Intext Questions 1. (i) State modern periodic law. (ii) Name the scientist who stated the law. (iii) How many groups and periods does modern periodic table have? 2. What are horizontal rows and vertical columns in a periodic table known as ? 3. Periodicity is observed due to similar (number of valence electrons/atomic number/electronic configuration). 4. How does the electronic configuration in atoms change (i) in a period from left to right ? (ii) in a group from top to bottom ? 5. Name two elements in each case: (i) Alkali metals (ii) Alkaline earth metals (iii) Halogens (iv) Inert gas 6. Elements of group 1 and elements of group 17 both have valency 1. Explain. (i) Elements in the same period have the same valency. (ii) Valency depends upon the number of shells in an atom. (iii) Copper and zinc are representative elements. (iv) Transition elements are placed at extreme right of the periodic table.. 7. What do you understand by? (i) Periodicity (ii) Typical elements (iii) Orbits 8. Name two elements that you would expect to show chemical reactions similar to calcium. What is the basis of your choice? 9. Name the (i) metals (ii) metalloids and (iii) non-metals in the first twenty elements. 10. Fluorine, chlorine and Bromine are put in one group on the basis of their similar properties. (i) What are those similar properties ? (ii) What is the common name of this group or family? 11. What is the main characteristic of the last element in each period of the Periodic Table? What is the general name of such elements? 12. According to atomic structure, what determines which element will be the first and which will be the last in a period? 13. How does the number of: (i) valence electrons and (ii) valency vary on moving from left to right in the third period of the periodic table? 14. Name the type of elements, which have their (i) outermost shell complete (ii) outermost shell incomplete (iii) two outermost shell incomplete (iv) one electron short of octet (v) two electrons in the outermost orbit. 15. An element has 2 electrons in its N shell. (i) What is its atomic number? (ii) State its position in periodic table (iii) Is it a metal or a non-metal? (iv) State the name assigned to this group. (v) What is the valency of this element? 16. Answer the following in respect of element 32 S. (i) Give its electronic configuration. (ii) To which group and period does it belong? (iii) What is its valency? (iv) Is it a metal or a non-metal? (v) Is it a reducing agent or an oxidising agent? (vi) Give its formula with hydrogen. 17. Name. (a) An alkali metal in period 3 and halogen in period 2. (b) The noble gas with 3 shells. (c) The non-metals present in period 2 and metals in period 3. (d) The element of period 3 with valency 4. (e) The element in period 3 which does not form oxide. (f) The element of lower nuclear charge out of Be and Mg. 18. The electronic configuration of an element T is 2, 8, 8, 1. (i) What is the group number of T? (ii) What is the period number of T? (iii) How many valence electrons are there in an atom of T? (iv) What is the valency of T? (v) Is it a metal or a non-metal? 19. Match the atomic number 19, 15, 8, 4 and 2 with each of the following: (i) A metal of valency one. (ii) A solid non-metal of period 3. (iii) A rare gas. (iv) A gaseous element with valency 2. (v) An element of group 2. 20. The elements are arranged in order of increasing atomic number (proton number). The vertical columns of elements with similar properties are called groups. The horizontal rows are called periods. Recurrence in properties due to same number of electrons are seen after a difference of 2, 8, 8, 18, 18 and 32 in atomic numbers. Properties of elements depend upon electrons in the valence shell (outermost orbit) so gradual change in properties is seen with increase in atomic number. Reactive metals are in group 1 and 2. Transition elements (metals) are in middle and non-metals in the upper right corner of the periodic table. Transition from metallic to non-metallic character is seen across a period.. ## 1.5 Periodic Properties - The properties of elements which are directly or indirectly related to their electronic configurations and show a regular gradation as we move across a period, from left to right or down the group from top to bottom, are called Periodic Properties. - Important periodic properties are : (i) atomic size (atomic radius), (ii) metallic character, (iii) non-metallic character, (iv) ionisation potential (ionisation energy), (v) electron affinity, (vi) electronegativity. ### 1.5.1 Atomic Size (Atomic Radius) - It is the distance between the centre of the nucleus of an atom and its outermost shell ## 1.5.2 Metallic Character - Those elements, which have a tendency to lose their valence electrons (electrons of the outermost orbit) and form a positive ion, are considered metals. ## 1.5.3 Non-metallic Character - Those elements which have a tendency to gain electrons, in order to attain octet in their outermost orbit, are considered as non-metals. ## 1.5.4 Ionisation Potential or Ionisation Energy (I.E.) or Ionisation Enthalpy - We know that the electrons in an atom are attracted by the positively charged nucleus. So, if we want to remove an electron from an atom, some energy has to be supplied to overcome the strong attraction of the nucleus. And after the electron gets removed from the atom, the atom then acquires one unit positive charge and becomes a positive ion (or cation). ## 1.5.5 Electron Affinity (E.A.) or Electron Gain Enthalpy - We have just studied that to remove an electron from an atom, energy is required. Similarly, when an extra electron is added to an atom, energy is released. ## 1.6 Comparison of Alkali Metals (Group 1) and Halogens (Group 17) | Category | Alkali Metals (Group 1) | Halogens (Group 17) | |---|---|---| | Elements | Li, Na, K, Rb, Cs, Fr | F, Cl, Br, I, At | | Occurrence | Occur in a combined state due to their reactive nature. | Occur in a combined state as salts, due to their reactive nature.. | | Physical state | Shiny white solid metals. They are shiny when freshly cut but soon become dull as they react with air. Soft and can be cut with a knife. Lithium is the hardest. | Non-metals (coloured); diatomic in the gaseous state. Fluorine (very reactive poisonous yellow gas) Chlorine (poisonous yellow green gas) Bromine (poisonous red brown volatile liquid) Iodine (dark grey crystalline solid). | | Valence Electrons | Possess one valence electron and therefore show similar properties. They form positive ion carrying a single charge eg. Na+ | Possess seven valence electrons each and therefore show similar properties. They form negative ion carrying a single charge e.g. Cl- | | Conduction and Nature | Good conductors of electricity. Highly reactive, electropositive metals. Metallic character increases from lithium (Li) to francium (Fr). | Non-conductors of electricity. Highly reactive, electronegative non-metals. Non-metallic character decreases from fluorine (F) to iodine (I). | | Melting point and boiling point | Decreases down the group. | Increases down the group. | | Atomic size | They have the largest atomic size in their period. The atomic size further increases down the group. | They have the smallest atomic size in their period. Atomic size increases down the group. | | Ionisation energy | They have lowest I.E. in their period. It decreases down the group. | They have high I.E. (lower than noble gases) in their period. | | Electron Affinity | They have low E.A. values which further decrease down the group. | They have high E.A. values. They too decrease down the group (exception: Cl has more E.A. than F). | | Electronegativity | They have the lowest E.N. in their period. E.N. decreases down the group. | They have high E.N. highest in their period. E.N. decreases down the group. | | Reactivity | They are reactive metals. Reactivity further increases down the group. | They are reactive non-metals. The reactivity decreases down the group. | | Reaction with water and acids| They react vigorously with water and acids liberating hydrogen. | Generally they do not react with dil. acids and water. | | Reducing/oxidising agents| Strong reducing agents as they lose electrons to complete their octet. | Strong oxidising agents as they accept electrons to complete their octet. | | Compound formation | Form electrovalent compounds with non-metals. Example: NaCl, KBr. | Form electrovalent compounds with metals. e.g., KCl, CaCl2. Form covalent compounds with hydrogen and other non-metals, e.g., HBr, HCl, HI,CCl4. | ## Exercise 1 1. What is the significance of atomic number in the modern periodic table? 2. Arrange the following as per instructions given in the brackets. (a) Mg, Cl, Na, S, Si (decreasing order of atomic size) (b) Cs, Na, Li, K, Rb (increasing metallic character) (c) Na, Mg, Cl, S, Si (increasing ionisation potential) (d) Cl, F, Br, I (increasing electron affinity) (e) Cs, Na, Li, K, Rb (decreasing electronegativity) (f) K, Pb, Ca, Zn (increasing reactivity) (g) Li, K, Na, H (decreasing order of their potential ionisation) 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? (b) Which 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. 5. Arrange the following in order of : (i) increasing radii. (a) Cl-, Cl (b) Mg2+, Mg, Mg+ (c) N, O, P (ii) increasing ionisation energy. (a) P, Na, Cl (b) F, O, Ne (c) Ne, He, Ar Explain your choice. 6. (a) Give reasons The oxidising power of elements increases from left to right along a period. (b) Select the correct answer (i) Across a period, the ionization potential [increases, decreases, remains same] (ii) Down the group, electron affinity [increases, decreases, remains same]. (c) Choose the correct answer from the choice given : (i) In the periodic table alkali metals are placed in the group A: 1, B: 11, C: 17, D: 18. (ii) 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. (d) State the group and period, of the element having three shells with three electrons in valence shell. 7. The electronegativities (according to Pauling) of the elements in Period 3 of the Periodic Table are as follows with the elements arranged in alphabetical order: Al 1-5 Cl 3-0 Mg 1-2 Na 0-9 P 2-1 S 2-5 Si 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). 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 a (lower/higher) electro-negativity than sodium and the element above chlorine would be expected to have a (lower/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). (c) On moving down a group, the number of valence electrons (remains the same/increases/decreases). (d) Metals are good (oxidising agent/reducing agent) because they are electron (acceptors/donors). 9. Parts (a) to (e) refer to changes 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 : (i) decreases, (ii) increases, (iii) remains the same, (iv) depends on the period (b) The electronegativity : (i) depends on the number of valence electrons, (ii) remains the same, (iii) decreases, (iv) increases. (c) The ionization potential : (i) goes up and down (ii) decreases (iii) increases (d) The atomic size : (i) decreases, (ii) increases, (iii) remains the same, (iv) remains the same (e) The electron affinity of the elements in groups 1 to 7: (i) goes up and then down. (ii) decreases and then increases, (iii) increases, (iv) decreases. 10. The elements of one short period of the Periodic Table are given below in order from left to right: Li Be B COFNe (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 elements belongs to the halogen series? 11. With reference to the variation of properties in the Periodic Table, which of the following is generally 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. 12. Atomic numbers of elements A, B, C, D, E, F are 8, 7, 11, 12, 13 and 9 respectively. State the type of ions they form. 13. (a) Formula of ion of A is A2+. Element A probably belongs to ........ group. (b) In a period, increase in electron affinity increases (oxidation/reduction). (c) On descending a group, (increase/decrease) in ionisation potential as well as electron affinity (increases/decreases) oxidising capacity. 14. Write the number of protons, neutrons and electronic configuration 2009 of 300K, P. Also state their position in the periodic table. 15. Name the element which has : (i) two shells, both of which are completely filled with electrons? (ii) the electronic configuration 2, 8, 3? (iii) a total of three shells with five electrons in its valence shell? (iv) a total of four shells with two electrons in its valence shell? (v) twice as many electrons in its second shell as in its first shell? 16. An element Barium has atomic number 56. Look up its position in the Periodic Table and answer the following questions. (i) Is it a metal or a non-metal? (ii) Is it more or less reactive than calcium? (iii) What is its valency? (iv) What will be the formula of its phosphate? (v) Is it larger or smaller than caesium (Cs) in size? 17. In group I of the Periodic Table, three elements X, Y and Z have ionic radii 1.33 Å, 0.95 Å and 0.60 Å respectively. Giving a reason, arrange them in the order of increasing atomic numbers in the group. 18. Explain why are the following statements not correct: (i) All groups contain metals and non metals. (ii) Atoms of elements in the same group have the same number of electron(s). (iii) Non-metallic character decreases across a period with increase in atomic number. (iv) Reactivity increases with atomic number in a group as well as in a period. 19. (i) State the number of elements in Period 1, Period 2, and Period 3 of the periodic table. Name them. (ii) What is the common feature of the electronic configuration of the elements at the end of Period 2 and Period 3? (iii) If an element is in Group 17, it is likely to be [metallic/non-metallic] in character, while with one electron in its outermost energy level (shell), then it is likely to be [metallic/non-metallic]. (iv) In Period 3, the most metallic element is (sodium/magnesium/aluminium). 20. Complete the following sentences choosing the correct word or words from those given in brackets at the end of each sentence: (i) The properties of the elements are a periodic (atomic number, mass number, relative atomic mass). (ii) Moving across a ..... of the Periodic Table the elements show increasing ........ character (group, period, metallic, non-metallic). (iii) The elements at the bottom of a group would be expected to show ....... metallic character than the element at the top (less, more). (iv) The similarities in the properties of a group of elements are because they have the same (electronic configuration, number of outer electrons, atomic numbers). 21. Give reasons for the following: (i) The size of a C ion is greater than the size of a Cl atom. (ii) Argon atom is bigger than chlorine atom. (iii) Ionisation potential of the element increases across a period. (iv) Inert gases do not form ion. 22. Answer the following questions.: (i) Identify the most electronegative element. (ii) Identify the most reactive element of group IA or 1. (iii) Identify the element from period 3 with least atomic size. (iv) How many valence electrons are present in Q. (v) Which element from group 2 would have the least ionization energy ? (vi) Identify the noble gas of the fourth period. (vii) In the compound between A and H what type of bond is formed and give its molecular formula. (c) Identify: The element which has the highest ionization potential. ## 1.5.6 Electronegativity (E.N.) - The tendency of an atom in a molecule to attract the shared pair of electrons towards itself is called its electronegativity. ## Exercise -1 - 1. What is the significance of atomic number in the modern periodic table? - 2. Arrange the following as per instructions given in the brackets. (a) Mg, Cl, Na, S, Si (decreasing order of atomic size) (b) Cs, Na, Li, K, Rb (increasing metallic character) (c) Na, Mg, Cl, S, Si (increasing ionisation potential) (d) Cl, F, Br, I (increasing electron affinity) (e) Cs, Na, Li, K, Rb (decreasing electronegativity) (f) K, Pb, Ca, Zn (increasing reactivity) (g) Li, K, Na, H (decreasing order of their potential ionisation) - 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? (b) Which 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. - 5. Arrange the following in order of : (i) increasing radii. (a) Cl-, Cl (b) Mg2+, Mg, Mg+ (c) N, O, P (ii) increasing ionisation energy. (a) P, Na, Cl (b) F, O, Ne (c) Ne, He, Ar Explain your choice. - 6. (a) Give reasons The oxidising power of elements increases from left to right along a period. (b) Select the correct answer (i) Across a period, the ionization potential [increases, decreases, remains same] (ii) Down the group, electron affinity [increases, decreases, remains same]. (c) Choose the correct answer from the choice given : (i) In the periodic table alkali metals are placed in the group A: 1, B: 11, C: 17, D: 18. (ii) 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. (d) State the group and period, of the element having three shells with three electrons in valence shell. - 7. The electronegativities (according to Pauling) of the elements in Period 3 of the Periodic Table are as follows with the elements arranged in alphabetical order: Al 1-5 Cl 3-0 Mg 1-2 Na 0-9 P 2-1 S 2-5 Si 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). - 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 a (lower/higher) electro-negativity than sodium and the element above chlorine would be expected to have a (lower/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). (c) On moving down a group, the number of valence electrons (remains the same/increases/decreases). (d) Metals are good (oxidising agent/reducing agent) because they are electron (acceptors/donors). - 9. Parts (a) to (e) refer to changes 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 : (i) decreases, (ii) increases, (iii) remains the same, (iv) depends on the period (b) The electronegativity : (i) depends on the number of valence electrons, (ii) remains the same, (iii) decreases, (iv) increases. (c) The ionization potential : (i) goes up and down (ii) decreases (iii) increases (d) The atomic size : (i) decreases, (ii) increases, (iii) remains the same, (iv) remains the same (e) The electron affinity of the elements in groups 1 to 7: (i) goes up and then down. (ii) decreases and then increases, (iii) increases, (iv) decreases. - 1

Periodic Table, Periodic Properties (PDF)

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