EL 3 Electrons, where would we be without them?

What are the subatomic particles in an atom?

Protons

neutrons

electrons

What is the maximum number of electrons in the first shell?

2

What is the maximum number of electrons in the second and third shells?

8

What is the Aufbau principle?

Electrons fill the lowest energy orbitals first.

What is Hund’s rule?

Electrons occupy orbitals singly before pairing up.

How many orbitals does the s sub-shell have?

1

How many orbitals does the p sub-shell have?

3

How many orbitals does the d sub-shell have?

5

How many orbitals does the f sub-shell have?

7

How many electrons can fit in a single orbital?

2

What shape does an s-orbital have?

Spherical

What shape does a p-orbital have?

Dumbbell

How does electronic configuration relate to the periodic table?

Periods indicate the number of occupied electron shells

and groups indicate the number of outer-shell electrons.

What causes the periodicity of elements?

Repeated patterns in their electronic structure.

Who proposed the first atomic theory?

John Dalton.

What model did J.J. Thomson propose?

Plum pudding model.

What experiment did Rutherford use to refine the atomic model?

Gold foil experiment

What was Niels Bohr’s contribution to atomic theory?

fixed energy levels.

What is the quantum mechanical model?

Electrons are located in orbitals not fixed paths.

What are the four stages of mass spectrometry?

Ionization

acceleration

deflection

detection.

What is ionization in mass spectrometry?

removing one or more electrons to form a positive ion.

What is the purpose of acceleration in mass spectrometry?

same kinetic energy

How are ions deflected in a mass spectrometer?

By a magnetic field depending on their mass-to-charge ratio (m/z).

What does the mass spectrum show?

The relative abundance of isotopes and their m/z ratio.

What is the difference between absorption and emission spectra?

Absorption shows missing wavelengths

emission shows emitted wavelengths.

Why is the 4s orbital filled before the 3d orbital?

lower energy

Why do d-block elements have complex configurations?

Energy levels of 3d and 4s orbitals are close

What is the significance of paired electron spins?

reduce repulsion and stabilize orbitals

What is the general rule for filling 3d and 4s orbitals?

4s orbital fills before 3d

When are electrons removed from 3d and 4s orbitals in ions?

Electrons are removed from the 4s orbital first because 4s becomes higher in energy than 3d after filling.

**Why does the 4s orbital fill before 3d in neutral atoms?

4s orbital has lower energy than 3d when empty

**Why does the 4s orbital lose electrons before the 3d orbital in ions?

** 3d orbital becomes lower in energy than 4s after electrons occupy the 3d subshell.

**What is special about chromium’s electron configuration?

** Chromium has the configuration [Ar] 3d⁵ 4s¹ because a half-filled 3d orbital is more stable than 3d⁴ 4s².

**What is special about copper’s electron configuration?

** Copper has the configuration [Ar] 3d¹⁰ 4s¹ because a fully filled 3d orbital is more stable than 3d⁹ 4s².

**Why do chromium and copper deviate from the Aufbau principle?

** They gain extra stability with half-filled (3d⁵) or fully filled (3d¹⁰) d-orbitals even though 4s loses one electron.

**What is the general stability rule for d-orbitals?

** Half-filled (d⁵) and fully filled (d¹⁰) d-orbitals are more stable due to symmetrical electron distribution.