Valence Electrons and Electron Configurations

This lecture covers electron configurations, explaining how electrons fill atomic orbitals based on energy levels and quantum numbers. The Aufbau principle is introduced to describe the order of filling. Examples of configurations for elements like hydrogen, helium, and oxygen are provided. The importance of valence electrons in chemical reactions is discussed, along with noble gas configurations. The lecture also explains how ions form by gaining or losing electrons, with a focus on transition elements.

What happens to the energy of an orbital as the principal quantum number increases?

• It fluctuates randomly

• It remains the same

• It increases

• It decreases

Which of the following has the lowest energy: s, p, d, or f orbitals?

• s

• p

• f

• d

In the electron filling order, which shell fills after 3p?

• 3d

• 4s

• 4p

• 5s

What does the superscript in an electron configuration represent?

• The energy level of the orbital

• The number of electrons in that orbital

• The type of orbital

• The principal quantum number

How many electrons can a p orbital hold?

• 2

• 8

• 4

• 6

What is the electron configuration for a hydrogen atom?

• 2p1

• 1s1

• 1s2

• 2s1

Why are valence electrons important in chemical reactions?

• They are the innermost electrons

• They interact with other atoms

• They are always stable

• They do not participate in reactions

What is the noble gas notation for the electron configuration of sodium?

• [Ne] 3s1

• [Ar] 3s1

• [He] 2s1

• [Ne] 2s1

When forming a positive ion, which electrons are removed first in transition elements?

• f electrons

• s electrons

• p electrons

• d electrons

What is the electron configuration for a phosphorus atom?

• 1s2 2s2 2p6 3s2 3p3

• 1s2 2s2 2p6 3s2 3p6

• 1s2 2s2 2p6 3s1 3p3

• 1s2 2s2 2p6 3s2 3d3