Electronic Configuration
What does an electron configuration describe?
The arrangement of electrons in an atom
How many total quantum numbers describe an electron?
4
Who created the first modern acceptable periodic table?
Dmitri Mendeleev
Does atomic size increase or decrease down a group?
Increases
Define electronegativity.
The ability of an atom to attract electrons
How many electrons can the 1s orbital hold?
2 electrons
Which quantum number (n, ℓ, mℓ, ms) describes energy level?
n (principal quantum number)
Mendeleev arranged elements by atomic mass. What does the modern table use?
Atomic number
Why does atomic size increase down a group?
More electron shells/energy levels
Define ionization energy.
Energy required to remove an electron
What is the electron configuration of Oxygen (atomic #8)?
1s² 2s² 2p⁴
What values can the spin quantum number (ms) have?
+½ or –½
What is a period in the periodic table?
A horizontal row
Does atomic size increase or decrease left to right across a period?
Decreases
Which element is the most electronegative?
Fluorine
Which rule says electrons fill the lowest-energy orbitals first?
Aufbau principle
If n = 3, what are the possible values of ℓ?
0, 1, 2
Why did Mendeleev leave gaps in his periodic table?
He predicted undiscovered elements
Why does atomic size decrease across a period?
Increasing nuclear charge pulls electrons closer
Do electronegativity & ionization energy increase or decrease across a period?
Increase
What is the electron configuration of Calcium (atomic #20)?
1s² 2s² 2p⁶ 3s² 3p⁶ 4s²
For n = 2 and ℓ = 1, how many orbitals exist?
3 orbitals (mℓ = –1, 0, +1)
Name the scientist who rearranged the periodic table by atomic number.
Henry Moseley
Which atom is largest: Na, Mg, Al?
Na (furthest left)
Explain why ionization energy increases across a period.
More protons → stronger attraction to electrons → harder to remove