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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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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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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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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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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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