Number of molecules in 1 dm³ Oxygen = 2.71 x 10²²
<h3>Further explanation</h3>
Conditions at T 0 ° C and P 1 atm are stated by STP (Standard Temperature and Pressure). At STP, Vm is 22.4 liters/mol.
The mole is the number of particles contained in a substance
1 mol = 6.02.10²³
1 dm³ of oxygen = 1 L Oxygen

n=mol=0.045
No = 6.02.10²³

B, sodium because if you look at your periodic table it is the only element not compounded with another
Answer:
Electron Geometry describes arrangement is electron groups & Molecular Geometry describes the arrangement of atoms
Explanation:
The picture above better explains it, hopefully this helps :)
The amount of heat required to change 25 grams of water into steam is 56425 joules or 13500 calories.