How do the chemical properties of oxides change from left to right across a period? from top to bottom within a particular group?

From left to right going in the periodic table the oxides form basic oxide at left and becomes acidic at right the oxides at center are amphotreric by nature 
like Na2O MgO are basic where As Cl2O7 SiO2 are acidic and ZnO etc are of dual nature that is they show both property of acidic and basic 
some oxides are neutral 
like CO 
N2O 
etc

Adozen is 12, and your needing to calculate the weight of one medium egg, so i would do 21/12=1.75 per egg, and check your answer by doing 1.75 * 12= 21 : ) : ): ): ): ) i hoped i