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Question
An element 'X' (Atomic number – 20) burns in the presence of oxygen to form a basic oxide.
(a) Identify the element and write its electronic configuration.
(b) State its group number and period number in the Modern Periodic Table.
(c) Write a balanced chemical equation for the reaction when this oxide is dissolved in water.
Solution
(a) The element 'X' is calcium (symbol Ca). Its electronic configuration is 2, 8, 8, 2.
(b) Group number and periodic number of Ca in the Modern Periodic Table are 2 and 4, respectively.
(c) Balanced chemical equation for the reaction when oxide of Ca is dissolved in water is given following as:
\[2 Ca + O_2 \to {2 CaO}_{\text{Calcium oxide}} \]
\[ {CaO}_{\text{Calcium oxide}} + {H_2 O}_{\text{Water}} \to {Ca(OH )_2}_{\text{Calcium hydroxide}}\]
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