Br 85 (a) Write the full electron configuration for an atom of bromine in the ground state. 1
l = 1
m_l = 2
Z_{eff}$? 1s.
Br 85 (a) Write the full electron configuration for an atom of bromine in the ground state. 1²²²²¹²2s²2p?3s²3p?4s²3d¹?4p?(b)Howmanyelectronsinabromineatomhavequantumnumberl = 1?6e?(c)Howmanyelectronsinabromineatomhavequantumnumberm_l = 2?2(d)Whichisbigger:onebromineatomoronebromideion?Explainwhy.BrorBr?bromideion.Anionsarebiggerthantheirneutralatoms(e)Whichhasalargerionizationenergy:bromineorpotassium?BrInabromineatom,electronsinwhichorbitalhavethelargestZ_{eff}$? 1s.
The Correct Answer and Explanation is:
Correct Answer:
(a) Full Electron Configuration for Bromine (Br), Atomic Number 35:
1s² 2s² 2p⁶ 3s² 3p⁶ 4s² 3d¹⁰ 4p⁵
Explanation
Bromine (Br) is a halogen with an atomic number of 35, meaning it has 35 electrons in its ground state. The electron configuration describes the distribution of electrons in various atomic orbitals, filled according to Aufbau’s principle (electrons fill lower energy orbitals first), Pauli’s Exclusion Principle, and Hund’s Rule.
Step-by-step filling of orbitals:
- 1s² → 2 electrons
- 2s² → 2 electrons
- 2p⁶ → 6 electrons
- 3s² → 2 electrons
- 3p⁶ → 6 electrons
- 4s² → 2 electrons
- 3d¹⁰ → 10 electrons
- 4p⁵ → 5 electrons
→ Total = 35 electrons
Thus, the configuration is:
1s² 2s² 2p⁶ 3s² 3p⁶ 4s² 3d¹⁰ 4p⁵
Quantum Numbers:
- The question mentions l = 1 and m_l = 2.
- l = 1 corresponds to a p orbital.
- m_l can range from –l to +l, i.e., –1, 0, +1 for p orbitals.
- So, m_l = 2 is invalid for l = 1.
⇒ No electron in a p orbital can have m_l = 2.
⇒ Likely a misinterpretation or typo.
Effective Nuclear Charge (Zₑₑf):
Effective nuclear charge (Zₑₑf) is the net positive charge experienced by an electron, accounting for shielding by inner electrons.
Using Slater’s rules or a simplified estimate:
- For a 4p electron in Br, Zₑₑf ≈ 35 – shielding ≈ 7–8
The valence electrons in 4p feel a reduced attraction due to shielding from inner shells (1s–3d). This reduced charge is why Br can easily gain 1 electron to form Br⁻.
Summary:
- Bromine ground-state configuration: 1s² 2s² 2p⁶ 3s² 3p⁶ 4s² 3d¹⁰ 4p⁵
- m_l = 2 is not valid for l = 1 (p orbital).
- Zₑₑf for 4p electron is approx. 7–8, explaining its chemical reactivity.
