Atomic Structure

Step 1: Calculate the molecular mass of
The molecular mass of a compound is the sum of the atomic masses of its elements.
- Atomic mass of sodium (Na) = 23 g/mol,
- Atomic mass of sulfur (S) = 32 g/mol,
- Atomic mass of oxygen (O) = 16 g/mol.
Step 2: Add the atomic masses
The molecular formula of sodium sulfate is ,
which contains: - 2 sodium atoms, - 1 sulfur atom, - 4 oxygen atoms.
Thus, the molecular mass is:
Answer:
Therefore, the molecular mass of is . So, the correct answer is option (1).

Step 1: Recall the electron configuration for oxygen
Oxygen (O) has an atomic number of 8, meaning it has 8 electrons.
Step 2: Distribute the electrons in orbitals
The electron configuration follows the Aufbau principle, which fills the lowest energy orbitals first:
- The first shell can hold up to 2 electrons, so the orbital is filled first: .
- The second shell can hold up to 8 electrons, so the orbital is filled next: .
- After that, the orbital starts filling.
Oxygen has 8 electrons in total, so the next 4 electrons will go into the orbital: .
Therefore, the electron configuration of oxygen is:
Answer:
Therefore, the correct electron configuration for an oxygen atom is . So, the correct answer is option (1).