How atoms stack their electrons

Science · Quantum & Modern Physics · ages 21-22

Name ______________________ Date ____________

Which set lists the four quantum labels of an electron?
- n, l, m, ms
- n, p, q, s
- x, y, z, t
Two electrons in one atom share the same n, l, and m. What must differ between them?
- Their shell number n
- Their spin direction ms
- Their electric charge
The first shell of an atom holds at most how many electrons?
Answer: ______________
Sodium and potassium sit in one column and react alike. Why?
- Both have the same outer shell filling
- Both are metals
- Both have the same mass
Oxygen has eight electrons. Which filling is correct?
- 1s2 2p6
- 1s3 2s2 2p3
- 1s2 2s2 2p4
Screening by inner electrons can make 4s fill before 3d.
Circle one: True False
Why do the transition metals appear where the d subshell starts filling?
- The nucleus gains extra protons all at once
- Atoms in that region lose their outer electrons
- Screening shuffles the order in which subshells fill
A student claims a neon atom fills as 1s2 2s2 2p7. What is wrong?
- Neon has no second shell
- The second shell holds at most eight electrons
- Electrons cannot sit in p orbitals

Answer key

For grown-ups. Fold this page away before handing over the rest.

n, l, m, ms · Shell, subshell shape, orientation, and spin are the four labels.
Their spin direction ms · All other labels match, so the spins must differ for the two electrons.
2 · Only two electrons fit in the first shell, as 1s2.
Both have the same outer shell filling · A shared outer filling gives a column its family resemblance.
1s2 2s2 2p4 · Two plus two plus four makes eight, filling lowest energy first.
True · Screening softens the nuclear pull and shuffles the fill order.
Screening shuffles the order in which subshells fill · The shuffled order stretches one period across the d subshell.
The second shell holds at most eight electrons · Two plus two plus seven is eleven electrons in a ten electron atom.