A lithium atom has three electrons, two in the 1s sublevel and one in the 2p sublevel.
The correct answer and explanation is:
A lithium atom has the electron configuration 1s² 2s¹, not 1s² 2p¹ as mentioned in your question. Here’s a breakdown of how this configuration is derived and why it is important.
Lithium (Li) has an atomic number of 3, meaning it has three protons in its nucleus and, in its neutral state, three electrons. The electron configuration describes how these electrons are arranged in orbitals around the nucleus.
The first two electrons of lithium go into the lowest energy orbital, the 1s orbital. This is because the 1s orbital has the lowest energy level and can hold a maximum of two electrons. Hence, the electron configuration for these two electrons is 1s².
After filling the 1s orbital, the third electron goes into the next available orbital, which is the 2s orbital. The 2s orbital also has the capacity to hold two electrons, but in the case of lithium, only one electron occupies this orbital. This results in the configuration 1s² 2s¹.
It is essential to note that electrons occupy orbitals in order of increasing energy levels. The 1s orbital is the lowest energy level, followed by the 2s orbital. The 2p orbital, which is higher in energy than the 2s orbital, is not occupied in a lithium atom in its ground state.
This electron configuration is important because it determines the chemical properties of lithium, such as its tendency to lose one electron to form a positive ion (Li⁺). The single electron in the 2s orbital is relatively far from the nucleus and is easily lost during chemical reactions, making lithium highly reactive, particularly with water and halogens.