1.) A compound is a thing that is composed of two or more (separate) elements.
2.) A compound cannot be separated easily, while its properties differ from where it originates from. It also is formed from chemical reactions.
3.) A pure substance, also known as chemical substance, is a material with constant composition and consistant properties. 
4.) If a substance is not a pure substance, then it is an impure substance.
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Answer:
An atom gets larger as the number of electronic shells increase; therefore the radius of atoms increases as you go down a certain group in the periodic table of elements. In general, the size of an atom will decrease as you move from left to the right of a certain period.
Explanation:
 
        
             
        
        
        
Answer:
The percent composition of dichlorine heptoxide is 38.76% CI and 61.24% O 
 
        
                    
             
        
        
        
Answer:
Protons and neutrons
Explanation:
The particles to forms the nucleus of an atom are the protons and neutrons of the atoms. 
These materials are located in the tiny nucleus and contributes the most mass of the atom. 
- Protons are the positively charged particles in an atom
- Neutrons do not carry any charges. 
- Sum of the protons and neutrons gives the mass number of the atom. 
 
        
             
        
        
        
Answer:
★ v = d/t
★ v = 90/30
★ v =3
<u>Acc</u><u> </u><u>to</u><u> </u><u>question</u>
★ momentum = mass * velocity
★ m = 25×3
★ m = 75kgm/s
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