Calcium is an element with atomic number 20.
(i) Is it a metal or non-metal?
(ii) Is it more reactive than Mg or less?
(iii) What will be its valency?
(iv) What will be the formula of its Chloride?
(v) Will it be larger than K or smaller?
(i) Ca is a metal because it contains 2 valence electrons. So it will lose these electrons to acquire stable noble gas electronic configuration.
Ca20- 2, 8, 8, 2
(ii) Yes, Ca is more reactive than Mg because the size of Ca is bigger than Mg. Due to this bigger size, the effective nuclear charge decreases so the attraction of nucleus on valence electrons decreases. So Ca will lose its valence electrons more easily than Mg.
(iii) Ca has two valence electrons so its valency will be 2.
(iv) Ca has two valence electrons and it will lose these two electrons so the formula of its chloride will be CaCl2.
(v) Ca is smaller than K because effective nuclear charge increases from left to right in a period. Due to this effective nuclear charge, the electronegativity increases and the attraction of the nucleus on valence shell electrons also increases. So the size decreases.