The atomic numbers of four elements P, Q, R and S are 6, 10, 12 and 17 respectively. Which two elements can combine to form a covalent compound ?

47 The atomic number of an element Y is 17. The number of electrons in its ion y^- will be : 48 The atomic numbers of four elements A, B, C and D are 6, 8, 10 and 12 respectively. The two elements which can react to form ionic bonds (or ionic compound) are: 50 The solution of one of the following compounds will not conduct electricity. This compound is: 51 The electronic configurations of three elements X, Y and Z are :

X : 2 Y : 2, 8, 7 Z : 2, 8, 2

Which of the following is correct regarding these elements ?