Chemistry
The atomic number of an element Z is 20. State
(a) the number of valence electron(s) in the element.
(b) the position of Z in the periodic table.
(c) whether the element is a metal or a non-metal.
(d) State the formula of the compound between Z and hydrogen.
Periodic Table
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Answer
(a) 2
(b) 4th period & Group 2
(c) Metal
(d) ZH2
Reason
(a) Electronic configuration is 2, 8, 8, 2 → 2 valence electrons (no. of electrons in outermost shell).
(b) Period: 4 (Because there are 4 shells: K, L, M, N - 2, 8, 8, 2).
Group: 2 (Because there are 2 valence electrons).
(c) Elements with 1, 2, or 3 valence electrons tend to lose them to achieve stability, which is a characteristic property of metals (electropositive nature).
(d) Valency of Z is 2, so it combines with hydrogen (valency 1) to form ZH₂ (By criss-cross method).
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