Two elements X and Y have atomic numbers 12 and 16 respectively. To which period of the modern periodic table do these two elements belong ?

"Properties of elements are the periodic function of their atomic number." (i) There are 18 groups. (ii) There are 7 periods in the modern periodic table.

S. No. Mendeleev's Period Table Modern Periodic Table (i) Elements have been arranged in increasing order of atomic masses. Element have been arranged in increasing order of their atomic number. (ii) It consists of 8 groups. It consists of 18 groups. (iii) All the groups from...

(i) Nitrogen: K shell-2       L shell-5 Phosphorus: K shell-2      L shell - 8       M    shell-5 (ii) Phosphorus will be less electronegative because its elections are further...

On moving from left to right in the periodic table valency increases up to 4 and then decreases. The electrons present in the last shell determine the valency of a particular element.  If...

(i) Na/Sodium.  Reason: The atomic size decreases from left to right due to the increase in the nuclear charge. (ii) AI/Aluminium. Reason: The tendency to Iose electrons decreases from left to right. Detailed Answer: (i) Na...

Sr. No. Property P o (i) No. of electrons in the atom 3 11 19 4 12 20 (any one pair) (ii) Size of the atom Bigger Smaller (iii) Metallic character More metallic Less metallic (iv) Tendency to lose electrons More More (v) Formula of oxides P2O QO (vi) Formula of chlorides PCI QCl2 Note: For parts (v) and (vi) examples using symbols of elements may also be accepted. Detailed Answer: (i) P...

Electronic configuration of Q = 2, 8,3 Valency of Q =3 Electronic Configuration of R = 2,8, 5 Valencyof R=8-5=3  Electronic configuration of P = 2,8,1 Electronic configuration of S=2,8,7  Formula : PS/NaCl

(i)They are in group 1 because all the elements in a group have 1 valence electron. They form positively charged ions by losing one electron.  (ii) Lithium is least reactive because the reactivity...

(i) Number of electrons in the outermost orbit of  X=1 and Y=2. (ii) Valency of X=1 and Y=2. (iii) Metal X is more metallic than Y. (iv) Atomic size of X is bigger than...