(a) Isotopes of cobalt – Treatment of cancer
Isotopes of cobalt are used in the treatment of thyroid cancer and some cancer which occurs rarely.
(b) Valency of nitrogen – Three
The atomic number of nitrogen = 7
The electronic configuration of 7N= 2,5
The valency of nitrogen is 3 because it combines with other element and receives three electros to complete the outermost shell (8-5=3)
(c) Non – metal – Receives electrons
Non- metals tend to receive electrons to complete their outermost shell. Outermost shell is the only shell which participates in the chemical reaction.
(d) Metal – loses electrons
Metals tend to loose electrons to complete their outermost shell.
(e) Valency – Electrons in the outermost orbit
Valency is the number of electrons in the outermost shell.
For example, carbon has 4 electrons in the outermost shell. Thus, the valency of carbon is 4.
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