L, M and N are three elements with atomic numbers 13, 7 and 10 respectively. Answer the following questions using only the alphabets given. Do not identify the elements.
Which element:
(a) can combine with hydrogen to form a gas which produces dense white fumes with concentrated HCl?
(b) has zero electron affinity?
(c) can form an ionic compound with oxygen?
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(a) M
Reason — Atomic number of element M is 7 so its electronic configuration is 2,5.Hence, it is a non-metal with 5 valence electrons. It combines with hydrogen to form a covalent hydride, MH3, which is a basic gas. MH3 reacts with concentrated HCl to give dense white fumes of ammonium salt.
(b) N
Reason — Atomic number of element N is 10 so its electronic configuration is 2, 8. It has electron affinity zero as it's octet is complete and it is a stable element.
(c) L
Reason — Atomic number of element L is 7 so its electronic configuration is 2, 8, 3. Hence, it is a metal with 3 valence electrons. Metals tend to lose electrons, and non-metals like oxygen tend to gain electrons, so L can transfer its 3 valence electrons to oxygen. This forms L3+ ions and O2- ions, giving an ionic compound with oxygen, generally of the form L2O3. So, L is the element that can form an ionic compound with oxygen.