(a)How do the properties of eka – aluminium element predicted by Mendeleev compare with the actual properties of gallium element? Explain your answer.
(b) What names were given by Mendeleev to the then undiscovered elements (i) scandium (ii) gallium, and (iii) germanium?
(a) The properties of eka-alumiunium, predicted by Mendeleev, which was undiscovered then, were almost similar to the actual properties of the element discovered later on. Eka-aluminium and gallium are the two different names given to the same element. Eka-aluminium has the same property like density, melting point, etc as the element gallium.
(b) (i) Scandium (Sc) was known as eka-boron.
(ii) Gallium(Ga) as eka-aluminium.
(iii) Germanium (Ge) as eka-silicon.
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- Besides gallium, which other elements have since been discovered that were left by Mendeleev in his periodic table?
- What physical and chemical properties of elements were used by Mendeleev in creating his periodic table? List two observations which posed a challenge to Mendeleev's Periodic Law.
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- Mendeleev predicted the existence of certain elements not known at that time and named two of them as eka-aluminium, and eka-silicon.(a) Name the element which has taken the place of (i) eka-aluminium, and (ii) eka-silicon (b) Mention the period/periods of these elements in the modern periodic table. (c) Write the group/ groups of these elements in the modern periodic table. (d) Classify these elements as metals, non-metals or metalloids. (e) How many valence electrons are present in the atoms of each of these elements?
- What were the criteria used by Mendeleev in creating his Periodic Table?
- Which one of the following is not a metalloid?(a) boron (b) silicon(c) gallium (d) germanium
- Which of the following are the correct characteristics of isotopes of an element?(i) same atomic mass(ii) same atomic number(iii) same physical properties(iv) same chemical properties(a) (i), (ii) and (iv)(b) (ii), (iii) and (iv)(c) (ii) and (iii)(d) (ii) and (iv)
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