There are three types of giant structure - ionic, metallic and macromolecular. Sodium nitride is an ionic compound. Draw a diagram that shows the formula of the compound, the charges on the ions, and the arrangement of the valency electrons around the negative ion. Use x to represent an electron from a sodium atom. Use o to represent an electron from a nitrogen atom.

Calcium carbonate is an important raw material. When calcium carbonate is heated strongly, it decomposes: ${\mathrm{CaCO}}_3 \to \mathrm{CaO} + {\mathrm{CO}}_2$. Calculate the relative formula mass of ${\mathrm{CaCO}}_3$.

Calcium carbonate is an important raw material. When calcium carbonate is heated strongly, it decomposes: ${\mathrm{CaCO}}_3 \to \mathrm{CaO} + {\mathrm{CO}}_2$. Calculate the relative formula mass of $\mathrm{CaO}$.

Calcium carbonate is an important raw material. When calcium carbonate is heated strongly, it decomposes: ${\mathrm{CaCO}}_3 \to \mathrm{CaO} + {\mathrm{CO}}_2$. $7.00 \mathrm{kg}$ of calcium oxide was formed. What mass of calcium carbonate was heated? 

Iron is a transition element. Which three of the following six statements about transition elements are correct?

(ii) The metals have low melting points.

Iron is a transition element. Is this given statement about transition elements correct?

(iii) Their compounds are highly coloured.

Iron is a transition element. Is this given statements about transition elements correct?

(iv) Their compounds are colourless.