Because size of an atom INCREASES from top to bottom and DECREASES from left to right on the periodic table. If to elements are in the same period they can't increase in size based on the up or down trend. Instead, notice that Alkali Metals are LEFT of Alkaline Earth Metals. Therefore, the Alkali Metal will be larger than the Alkaline Earth Metals.
During a combustion reaction the carbon in a hydrocarbon compound is paired with Oxygen (O2) in the air to form Carbon-Dioxide (CO2), whilst the Hydrogen too pairs with Oxygen to form water vapour (H2O). Heat is also produced during this reaction.
179.4 g will be formed from 123g of iron
