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.
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).
Related Questions
First ionisation enthalpy of two elements X and Y are 500 kJ mol-1 and 375 kJ mol-1 respectively. Comment about their relative position in a group as well as in a period.
The elements of one short period of the Periodic Table are given below in order from left to right :
Li Be B C O F Ne
(a) To which period do these elements belong ?
(b) One element of this period is missing. Which is the missing element and where should it be placed ?
(c) Place the three elements fluorine, beryllium and nitrogen in the order of increasing electronegativity.
(d) Which one of the above elements belongs to the halogen series ?
M is a metal and its oxide has the formula M2O. This oxide when dissolved in water forms the corresponding hydroxide which is a good conductor of electricity. In the above context, answer the following :
(i) State the number of electrons in the outermost shell of M ?
(ii) Name the group to which M belongs.
(iii) which element has more electronegativity, M or O?
The metals of Group 2 in the periodic table from top to bottom are — Be, Mg, Ca, Sr, and Ba.
(i) Which one of these elements will form ions most readily and why?
(ii) State the common feature in the electronic configuration of all these given elements.