In urea, each nitrogen atom uses three of its valence electrons for formation of single bonds with carbon atom and two hydrogen atoms.
Catalyst has found usage in non-scientific terms as an almost metaphorical word for something provokes or speeds up action or change. The word's applicability to many topics made it easy for it to find its way out of the scientific lexicon and into other domains, in this case political.
Its meaning is roughly the same, in that a catalyst in this context is something that facilitated or sped up the process of glasnost.
One distinct meaning that I notice is that "catalyst" in more casual or non-scientific speech is that it is often used as a creator of action all its own, an actor in itself, rather than a facilitating agent to a reaction, as its scientific definition states.
elements in the periodic table are arranged by the atomic number of the element
The correct answer is A MODEL OF MOUNTAIN FORMATION.
A model refers to a representation of an idea, a process or a system, which is used to explain a specific phenomenon that can not be experienced directly. Models are often used in science to explain many phenomenon. When we are talking about a suitable model to represent an event that happens slowly, the most obvious choice from the options given above is mountain formation. This is because, the process of mountain formation occurs very slowly over a long period of time.
