What is the electronic configuration (shell by shell) of the element Ar (atomic number 18)?
Answer and explanation
Correct answer: A. 2,8,8
- Step 1: Fill the shells in order: 2 in the first, 8 in the second, 8 in the third. Step 2. 18 electrons give 2,8,8. Answer: 2,8,8. Why not the others: 2,8,8,1 is what you get if you count one or two electrons too many or too few. 2,8,7 is what you get if you count one or two electrons too many or too few. 2,8,8,2 is what you get if you count one or two electrons too many or too few.
Practise more Physics and chemistry.
Free questions with an explanation for every one, and full timed DTM University Entrance Test (Uzbekistan) mock tests.
More Physics and chemistry questions
- Which unit is used for force in the SI system?
- A car moving at 20 m/s accelerates at 2 m/s² for 5 s. What is its final speed?
- A resistor of 6 Ω carries a current of 2 A. What is the voltage across it?
- What is the kinetic energy of a 2 kg object moving at 3 m/s?
- A stone falls from rest for 2 s. Taking g = 10 m/s², how far does it fall?
- Which part of the electromagnetic spectrum has the highest frequency?