(a) State the periodic law on which Mendeleev’s periodic table was based. Why and how was this periodic law changed ?(b) Explain why, the noble gases are placed in a separate group.
(a) According to Mendeleev’s periodic law, the properties of elements are a periodic function of their atomic masses. After was the discovery of atomic numbers, Mendeleev’s periodic law was changed, which was based on atomic mass to atomic number.
(b) Noble gases (having completely filled outermost electron shells) are chemically inert or unreactive elements so they were placed in a different group.
Related Articles
- State the Periodic Law on which the Modern Periodic Table is based.
- (a) State Mendeleev’s periodic law.(b) What chemical properties of elements were used by Mendeleev in creating his periodic table? (c) State any three limitations of Mendeleev’s classification of elements. (d) Besides gallium, which two other elements have since been discovered for which Mendeleev had left gaps in his periodic table ? (e) Which group of elements was missing from Mendeleev’s original periodic table?
- Why do you think the noble gases are placed in a separate group?
- (a) State modern periodic law.(b) How does the electronic configuration of the atom of an element relate to its position in the modern periodic table? (c) How could the modern periodic law remove various anomalies of Mendeleev’s periodic table? Explain with examples. (d) Is it possible to have an element having atomic number 1.5 placed between hydrogen and helium ? (e) Name the scientist who prepared modern periodic table.
- Who was the inventor of Periodic Table?
- How could the modern periodic table remove various anomalies of Mendeleev’s Periodic Table?
- Compare and contrast the arrangement of elements in Mendeleev’s Periodic Table and the Modern Periodic Table.
- Which group of elements could be placed in Mendeleev’s ′ Periodic Table without disturbing the original order? Give reason.
- Which of the following statement (s) about the Modern Periodic Table are incorrectThe elements in the Modern Periodic Table are arranged based on their decreasing atomic numberThe elements in the Modern Periodic Table are arranged based on their increasing atomic massesIsotopes are placed in adjoining group (s) in the Periodic TableThe elements in the Modern Periodic Table are arranged based on their increasing atomic number(a) (i) only(b) (i), (ii) and (iii)(c) (i), (ii) and (iv) (d) (iv) only
- According to Mendeleev’s Periodic Law, the elements were arranged in the periodic table in the order of(a) increasing atomic number(b) decreasing atomic number(c) increasing atomic masses(d) decreasing atomic masses
- Who discovered Periodic Table? How was it made? How is this helpful to us?
- (a) How does the electropositive character of elements change on going down in a group of the periodic table?(b) State how the valency of elements varies (i) in a group, and (ii) in a period, of the periodic table.
- (a) List any three observations which posed a challenge to Mendeleev’s Periodic law.(b) How does the metallic character of elements vary on moving from(i) left to right in a period,(ii) from top to bottom in a group of the Modem Periodic Table?Give a reason for your answer.
- State whether the following statement are true or false:(a) Newlands divided the elements into horizontal rows of eight element each. (b) According to Mendeleev’s periodic law, the properties of elements are a periodic function of their atomic numbers. (c) The elements in a group have consecutive atomic numbers.
- (a) Why do we classify elements?(b) What were the two criteria used by Mendeleev to classify the elements in his periodic table? (c) Why did Mendeleev leave some gaps in his periodic table? (d) In Mendeleev’s periodic table, why was there no mention of noble gases like helium, neon and argon? (e) Would you place the two isotopes of chlorine, Cl-35 and Cl-37 in different slots because of their different atomic masses or in the same slot because their chemical properties are the same? Justify your answer.
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