Answer: 
Explanation:
A double displacement reaction is one in which exchange of ions take place. The salts which are soluble in water are designated by symbol (aq) and those which are insoluble in water and remain in solid form are represented by (s) after their chemical formulas.
The balanced chemical equation when when aqueous solutions of chromium(III) sulfate and calcium nitrate are combined is:

Answer:
C) An electron has a negative charge and is located outside the nucleus.
Answer:
For (a) the independent variable is what stays constant throughout the whole experiment and the dependent variable is changes in the experiment.
Explanation:
I'm not sure about the other parts, but I hope my explanation for a can get you started :)
D the strength of both acid and base
Covalent bonding - giant covalent structures. ... The atoms are usually arranged into giant regular lattices - extremely strong structures because of the many bonds involved. The graphic shows the molecular structure of diamond and graphite: two allotropes of carbon, and of silica.