The highest number of helium atoms is in

To determine which option contains the highest number of helium atoms, we can calculate the number of atoms present in each given option using the concept of moles and Avogadro's number ($N_A\approx 6.022\times {10}^{23}$ atoms/mol). The molar mass of helium (He) is 4 g/mol, and its atomic mass is 4 u.

Let's analyze each option step-by-step:

1. 4 mol of helium:
Using the definition of a mole, the number of atoms in 4 moles of helium is calculated as:
$\text{Number of atoms}=\text{Moles}\times N_A$
$\text{Number of atoms}=4\times 6.022\times {10}^{23}\approx 2.41\times {10}^{24}\text{atoms}$

2. 4 u of helium:
The term "u" stands for unified atomic mass unit. The mass of a single helium atom is approximately 4 u.
Therefore, 4 u of helium represents exactly 1 helium atom.

3. 4 g of helium:
First, we find the number of moles in 4 g of helium:
$\text{Number of moles}=\frac{\text{Given mass}}{\text{Molar mass}}=\frac{4\text{g}}{4\text{g/mol}}=1\text{mol}$
The number of atoms in 1 mole of helium is:
$\text{Number of atoms}=1\times N_A\approx 6.022\times {10}^{23}\text{atoms}$

4. 2.271098 L of helium at STP:
Under modern IUPAC STP conditions (temperature of 273.15 K and pressure of 1 bar), the molar volume of an ideal gas is 22.71098 L/mol.
First, calculate the number of moles:
$\text{Number of moles}=\frac{\text{Volume at STP}}{\text{Molar volume}}=\frac{2.271098\text{L}}{22.71098\text{L/mol}}=0.1\text{mol}$
Now, find the number of atoms:
$\text{Number of atoms}=0.1\times N_A\approx 6.022\times {10}^{22}\text{atoms}$

Comparing the values:
- 4 mol of helium contains approximately $2.41\times {10}^{24}$ atoms.
- 4 u of helium contains 1 atom.
- 4 g of helium contains approximately $6.022\times {10}^{23}$ atoms.
- 2.271098 L of helium at STP contains approximately $6.022\times {10}^{22}$ atoms.

Thus, the highest number of helium atoms is present in 4 mol of helium.