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The atom is the basic unit of matter which goes into in a chemical reaction

a. Substances react together producing new substances. The activity which changes the substance into a new material is called chemical reaction.

b. An atom is the unit of the substance which undergoes a chemical reaction.

c. An atom that has less than 8 electrons in the last energy level is active.

It reacts with atoms of other elements to complete the last energy level with 8 electrons.
An example:
sodium atoms are active because each has an electron in the last energy level. In a chemical reaction sodium gives this electrons to atoms of another element & end up with 8 electrons in the last energy level.

d. Inert gases such as Argon 18Ar has 8 electrons in the last energy level. They are stable & don’t react with other substances.

 



I. Fill in the blanks:

Name Symbol No. of protons No. of neutrons Electronic configuration
Hydrogen      
       
       
       
       
       

 

II. Give reasons:

1. The atom is electrically neutral.

………………………………………………………………………………………………………………………………………………………………………………………………………….

2. The mass number is greater than the atomic number.

…………………………………………………………………………………………………………………………………………………………………………………………………………

 



3. The 3rd energy level in the atom contains 18 electrons.

………………………………………………………………………………………………………………………………………………………………………………………………………….

4. The equation 2n2 isn’t applied to the 4th energy level.

………………………………………………………………………………………………………………………………………………………………………………………………………….

5. 10Ne doesn’t go into chemical reactions.

……………………………………………………………………………………………………………………………………………………………………………………………………….

6. The mass of the atom is concentrated in the nucleus.

………………………………………………………………………………………………………………………………………………………………………………………………………….

III. Write the scientific term:

1. The number of protons in the atom.  
   
2. The sum of no. of protons & neutrons in the nucleus.  
   
3. The basic unit of matter that takes part in a chemical reaction.  
   
4. Negatively charged particles that revolves around the nucleus.  

 

IV. Choose the right answer:

1. The second energy level in 7N contains………….electrons.

(2 – 3 – 5)

2. The chemical activity of the element depends on the number of …………………….

(electrons in the outer level – protons – neutrons )

3. All the following elements are chemically active except…………………

(1H – 6C – 18Ar)

 



V. Figure………………………is an excited atom while, figure…………………is for the atom in the ground state.

           
 
     
 

 




Figure A Figure B

 



 




Date: 2015-12-24; view: 733


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