CBSE Class 10 Science 2017 · Paper 31/2/1 · Question 10
The atomic number of an element is 20.
- (a)Write its electronic configuration and determine its valency.
- (b)Is it a metal or a non-metal ?
- (c)Write the formula of its chloride.
- (d)Is it more reactive or less reactive than Mg (atomic number 12) ? Give reason for your answer.
Answer
The element is calcium (): valency 2, a metal, chloride , and more reactive than magnesium.
(a) Electronic configuration: K, L, M, N . It has valence electrons, which it loses, so its valency is .
(b) It is a metal (it is calcium, in group 2).
(c) Its chloride is .
(d) It is more reactive than magnesium. Magnesium () and this element are both in group 2, but this element has one more shell, so its valence electrons are farther from the nucleus and are lost more easily.
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