Here is an image of the periodic table. Hope this helps.
<u>a) Answer: </u>
<em>Number of molecules in 1 mole</em>
<u>Explanation:</u>
a) Whether we take any of the substance among all three of the given substances they will have the same number of molecules in 1 mole of the substance is considered and the value for this will be 
<u>b) Answer: </u>
<em>In the given question </em><em>mass of the substance</em><em> which is </em><em>greatest</em><em> is asked for </em><em>one mole</em><em> and we also know that </em><em>mass of one mole is given by molar mass. </em>
<u>Explanation:</u>
b) It is known that
is the molar mass for oxygen which is greater than that of hydrogen while fluorine has a molar mass of
which on comparison shows that, it is the highest amongst all three.
The elements in the periodice table are not listed in alphabetical order, because the arragement in rows (periods) and columns (groups or familes), in increasing order of atomic number (number of protons of the atoms) permits to explain similarities among the elements, trend in some properties, and even predict properties of unknown elements.
For example, the elements of the first group (family), called alkaline metals, all have 1 valence electron, have similar physical properties (ductibility, malleability, luster, thermal and electricity conductivity), react in similar way with water, show a trend in the atomic radii and in the ionization energy.
You can tell similar stories for other groups like, alkalyne earth metals, halogens and noble gases.
You can also tell trends in electroneativities, and atomic radii, for a row of elements, as per the order they are in the row.
So, the current array resulted very helpul for chemists to explain and predict the behavior and properties of the elements.
The calculation for such a question can be achieved via Avogadro hypothesis
We know molar mass of CO2 is 44g/mole which is the sum of atomic masses i.e; C and 2 oxygen atoms
Molar mass of CO2 =12(C)+2*16(O) = 44 g/mole will contain 6.023 ※10^23 CO2 molecules ..
44g/mole = 6.023 ※10^23 CO2 molecules
=> 1g = (6.023/44) ※10^23 CO2 molecules
==> 8.80g = 8.80(6.023÷44)10^23 = 1.2046 ※10^23 molecules of CO2….
Thus there r 1.2046 ※10^23 molecules of CO2 in 8.80g
if u need to calculate no. of carbon atoms then multiply result by 1 and if u need no of oxygen atoms in 8.80g of co2 then multiply the result by 2 ….