Determine the energy levels of electrons for the first 20 elements. Explain the relevance of valence electrons in y2kcenter.orgical processes. Identify the number of valence electrons in an element. Describe the stability of an atom as a result of following the octet rule.
You are watching: What is the element with the electron arrangement 2,8,7?
The structure of the atom was discussed in the previous unit and now we will focus on the role that electrons play in the formation of compounds. Regardless of the type of compound or the number of atoms or electrons involved, it is the electrons of those atoms that interact to form a compound.
Electrons are not randomly arranged in an atom and their position within the atom can be described using electron arrangements, which are a simplified version of electron configurations. For each element of interest, we look at the number of electrons in a single atom and then determine how those electrons are arranged based on the atomic model. The main idea behind electron arrangements is that electrons can only exist at certain energy levels. By understanding the energy levels of electrons in an atom, we can predict properties and understand behavior of the atom.
As shown in the figure below, there are multiple energy levels where electrons can be found. As the energy level increases, the energy difference between them decreases. A maximum of two electrons can be found in the (n=1) level; eight electrons can be in the (n=2) level. Although the (n=3) and (n=4) levels show only eight electrons in this diagram, those energy levels can hold more but not until we start looking at the transition metals. We will only be concerned with the electron arrangements of elements through calcium (left( Z = 20
ight)) so we will put a maximum of eight electrons in the (n=3) level and two in the (n=4) level.