Question

according to the aufbau principle, electrons fill orbitals in which order?
a) randomly
b) based on increasing principal quantum number
c) based on increasing energy levels
d) based on decreasing energy levels

hunds rule states that electrons prefer to occupy degenerate orbitals:
a) singly with parallel spins
b) singly with opposite spins
c) in pairs with parallel spins
d) in pairs with opposite spins

1. which of the following elements demonstrates a deviation from expected electronic configuration due to stability gained from half - filled or fully - filled subshells?

a) sodium (na)
b) chromium (cr)
c) magnesium (mg)
d) nickel (ni)

1. the periodic trend in atomic radius across a period can be attributed to:

a) decreasing nuclear charge
b) increasing electron shielding
c) increasing number of protons
d) decreasing number of valence electrons

1. ionization energy tends to increase across a period due to:

a) decreased nuclear charge
b) increased atomic radius
c) increased electron affinity
d) increased effective nuclear charge

Explanation:

1. The Aufbau Principle states that electrons fill orbitals in order of increasing energy levels.
2. Hund's Rule states that electrons prefer to occupy degenerate orbitals singly with parallel spins to maximize spin - multiplicity and stability.
3. Chromium (Cr) has a deviation from the expected electronic configuration because of the stability gained from a half - filled 3d subshell. Its configuration is [Ar] 3d⁵4s¹ instead of [Ar] 3d⁴4s².
4. The periodic trend in atomic radius across a period is due to the increasing number of protons which leads to a greater effective nuclear charge pulling the electrons closer, thus decreasing the atomic radius.
5. Ionization energy tends to increase across a period due to the increased effective nuclear charge which makes it harder to remove an electron.

Answer:

1. c) Based on increasing energy levels
2. a) Singly with parallel spins
3. b) Chromium (Cr)
4. c) Increasing number of protons
5. d) Increased effective nuclear charge