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Did Dobereiner’s triads also exist in the columns of Newlands’ Octaves? Compare and find out
In the dobereiner's triads, the middle element atomic mass is equal to the avaerage atomic mass of the first and third element. only one Dobereiner’s triads is exist in the columns of Newlands’ Octaves.
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What were the limitations of Dobereiner’s classification?
Limitation of Dobereiner’s Classification: Only few elements can be arranged in the Dobereiner's traids. It depends on their properties. F, Cl, Br will not show the traids but Cl , Br, I will show.
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What were the limitations of Newlands’ Law of Octaves?
Limitations of Newlands’ law of octaves: (i) It was applicable upto lighter element (Calcium only). (ii) The properties after calcium does not have any resemblance to the properties of the above element. (iii) Co and Ni are transition elements but they were placed in the group of F, Cl. (iv)Iron properties are similar to the cobalt and nickel but placed in different column
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Use Mendeleev’s Periodic Table to predict the formulae for the oxides of the following elements: K, C, Al, Si, Ba.
Potassium is in group 1. The oxide will be K2O. Carbon is in group 4. The oxide will be CO2. Aluminium is in group 3. The oxide will be Al2O3. Silicon is in group 4. The oxide will be SiO2. Barium is in group 2. The oxide will be BaO
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Besides gallium, which other elements have since been discovered that were left by Mendeleev in his Periodic Table? (any two)
Gallium and Scandium
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What were the criteria used by Mendeleev in creating his Periodic Table?
Mendeleev’s periodic table was based on the atomic masses of the elements. The properties of the elements are the periodic function of their atomic masses. Elements are arranged in the increasing atomic mass and their properties get reoccur after regular intervals
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Why do you think the noble gases are placed in a separate group?
Noble gases are inert gases. Noble gases does not form any compounds due to inert nature. Their periodic properties are different from all other elements.
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How could the Modern Periodic Table remove various anomalies of Mendeleev’s Periodic Table?
In 1913, Henry Moseley showed that the atomic number of an element is a more fundamental property than its atomic mass. Position of isotopes of various elements decided in the modern periodic table. Position of Cobalt and Nickel resolved in the modern periodic table. Elements of same group show marked similarities due to similar outer electronic configuration.
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Name two elements you would expect to show chemical reactions similar to magnesium. What is the basis for your choice?
Strontium (Sr) and Barium (Ba) are expected to show chemical reactions similar to magnesium (Mg) because these elements have the two valence electrons in the valence shell. Due to the same valence electrons elements show same chemical reactions.
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Name (a) three elements that have a single electron in their outermost shells. (b) two elements that have two electrons in their outermost shells. (c) three elements with filled outermost shells.
(a) Lithium (Li), potassium (K) and rubidium (Rb) have a single electron in their outermost shells. (b) Barium (Ba) and calcium (Ca) have two electrons in their outermost shells. (c) Neon (Ne), argon (Ar), and xenon (Xe) elements have filled outermost shells.
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(a) Lithium, sodium, potassium are all metals that react with water to liberate hydrogen gas. Is there any similarity in the atoms of these elements? (b) Helium is an unreactive gas and neon is a gas of extremely low reactivity. What, if anything, do their atoms have in common?
(a) Yes, all the three elements lithium, sodium, and potassium have one electron in the valence shells. (b) Helium (He) and neon (Ne) are inert gas. their outermost shells are completely filled. Helium has a duplet in its K shell, while neon has an octet in its K, L shell
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In the Modern Periodic Table, which are the metals among the first ten elements?
Lithium (Li) and beryllium (Be) are metals among the first ten elements.
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By considering their position in the Periodic Table, which one of the following elements would you expect to have maximum metallic characteristic? Ga, Ge, As, Se and Be
Be and Ga are expected more metallic but Metallic character increase when we goes from top to bottom. Due to more size for galium, it is the most metallic among the given elements.
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Which of the following statements is not a correct statement about the trends when going from left to right across the periods of periodic Table (a) The elements become less metallic in nature. (b) The number of valence electrons increases. (c) The atoms lose their electrons more easily. (d) The oxides become more acidic.
(c) The atoms lose their electrons more easily. (In the period, the atoms size decreases so difficult to lose their electrons.)
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Element X forms a chloride with the formula XCl2, which is a solid with a high melting point. X would most likely be in the same group of the Periodic Table as (a) Na (b) Mg (c) Al (d) Si
(b) Valency of X in the given compound is 2. Mg is in the group 2 in the Periodic Table.
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Which element has (a) two shells, both of which are completely filled with electrons? (b) the electronic configuration 2, 8, 2? (c) a total of three shells, with four electrons in its valence shell? (d) a total of two shells, with three electrons in its valence shell? (e) twice as many electrons in its second shell as in its first shell?
(a) Neon has two shells, both of which are completely filled with electrons (b) Magnesium electronic configuration is 2, 8, 2. (c) Silicon has a three shells, with four electrons in its valence shell (d) Boron has a two shells, with three electrons in its valence shell (e) Carbon has twice as many electrons in its second shell as in its first shell
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(a) What property do all elements in the same column of the Periodic Table as boron have in common? (b) What property do all elements in the same column of the Periodic Table as fluorine have in common?

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An atom has electronic configuration 2, 8, 7. (a) What is the atomic number of this element? (b) To which of the following elements would it be chemically similar? (Atomic numbers are given in parentheses.) N(7) F(9) P(15) Ar(18)
(a) Atomic number of the given configuration is 17. (b) Flourine electronic configuration is 2,7. Same number of valence electrons in the outermost shell
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Nitrogen (atomic number 7) and phosphorus (atomic number 15) belong to group 15 of the Periodic Table. Write the electronic configuration of these two elements. Which of these will be more electronegative? Why?
The electronic configuration of the group 15 elements. i Element Atomic number K, L, M Nitrogen 7 2,5 Phosphorous 15 2,8,5 Electronegativity is the tedency of an atom of an element in a molecule to attract the shared pair of electron present between bonded atoms towards itself. when we move from left to right electronegativity increases and when we move from top to bottom the E.N decreases. In case of group 15, the electronegativity decreases. Nitrogen is more electronegative than phosphorous
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How does the electronic configuration of an atom relate to its position in the Modern Periodic Table
In the modern periodic table, the period number of an element is equal to the number of shells in its atom. the group number of an element having upto two valence electrons is equal to the number of valence electrons. if more than two valence electrons is equal to the number of valence electrons plus 10.
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In the Modern Periodic Table, calcium (atomic number 20) is surrounded by elements with atomic numbers 12, 19, 21, and 38. Which of these have physical and chemical properties resembling calcium?

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Compare and contrast the arrangement of elements in Mendeleev’s periodic Table and the Modern Periodic Table

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