Chemistry - 9 Chapter - 3
Atomic Structure
Test - 1

1. The idea that matter is made up of very small particles was first proposed by ____ in _____




2. The word postulate means Something assumed true?


3. Define element? Short..Answer.......................................... Element is a substance in which all atoms are similar, having same atomic number and cannot be divided into simpler substances by chemical methods.Total ----- elements exist which include -- natural and --- artificial.




4. Define Atom? Short..Answer.............................................. Atom is the smallest, invisible and distinct part of an element, which contains all properties of that element, and cannot be further sub divided by ordinary means. It is made up of a positively charged nucleus surrounded by electrons in various orbits. Atoms ----------------------- in chemical reactions.



5. Define Nucleus? Short..Answer.............................................. Central part of an atom containing protons and neutrons, where most of its mass is concentrated. Its size is very small as compared to the size of atom. It has --------- around it where electrons circulate.



6. Define Proton? Short..Answer.............................................. It is the smallest positively charged particle present in all kind of atoms. The mass of this particle is equal to the mass of -------- nucleus (H+).




7. What is Neutron? Short..Answer............................................ It is the smallest -------- particle present in the nucleus of atoms. Its mass is slightly more than that of a proton



8. Define Mass Number ( Atomic Mass )? Short..Answer.............................................. The Atomic Mass or Mass Number is total number of ------------------------------- present in the nucleus of an atom.



9. Define Atomic Number? Short..Answer................................................ Number of --------- charged particles (protons) present in the nucleus of an atom.



10. Define Atomic Spectrum? Short..Answer................................................... Atomic Spectrum is spectrum of radiations emitted by the -------- atoms when they come to the normal state.




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