Water — CHEMISTRY STD 9 — Question

Amongst the chlorine atom and chlorine molecule, which has more energy and why?

Covalent bonds can be single, double or triple covalent bonds. How many electrons are shared in each? Give an example of each type.

Give reason for the following:
Potassium and sodium are not used for reaction with dilute hydrochloric acid or dilute sulphuric acid in the laboratory preparation of hydrogen.

Give an example of the following chemical changes.
An exothermic and an endothermic reaction involving carbon as one of the reactants.

Explain the following:
Atoms combine by transfer and sharing of an electron(s).

Element P has atomic number 19. To which group and period, does P belong? Is it a metal or a non-metal? Why?

An element is represented by symbol X?
(a) What is the mass number and atomic number of element X?
(b) Name its valence shell and number of electrons in the valence shell.
(c) Is the clement a metal or a non-metal?

Name five conditions for a chemical reaction. Support your answer by at least one example each.

Why do the isotopes of same elements have similar chemical properties?