Energy Levels and Electronic Configuration Chemistry the virtual school

In a previous video we learned that the nucleus is in the center of an atom and that it is made up of protons and neutrons and around this central point are the electrons. We also know that in a neutral atom the number of electrons is always equal to the number of protons, so in a neutral carbon atom there are six protons, which means there must be six electrons, the electrons in the atom are organized around the nucleus in different

energy

levels

or shells, the shells can only hold a certain amount of electrons, the first and the second.

The innermost shell can only contain a maximum of two electrons. The shells that come after can contain a maximum of eight electrons. Let's look at some arrangements. Lithium has three protons, therefore it has three electrons. The first two electrons are placed in the first most shell. close to the nucleus and the third electron is placed in the second shell 2 + 1 three electrons these diagrams are called dot and cross diagrams and are used to show the

electronic

configuration

of an element, you need to be able to draw these diagrams as well as being able to write the electron

configuration

in written form for lithium, this will be written as Li I 21 in the diagram the nucleus is represented by the element symbol or a central black dot the

energy

levels

are represented by circles around the nucleus and the electrons are represented by dots or crosses let's look at some more examples carbon has six protons therefore it has six electrons the first two electrons are placed in the first shell and the next four are placed in the second shell 2 + 4 six electrons this would be written as c 2 4 magnesium has 12 protons therefore it has 12 electrons the first two are placed in the first shell the next eight are placed in the second shell and the last two are placed in the third shell 2 + 8 + 2 12 electrons this would be written as mg 2 82 the organization of these energy levels is what gives the elements their different reaction activities the number of electrons in the outer sh atom tells you the group number to which members of the same group belong on the periodic table with the same number The electrons in the outer shell have similar reactivities, so the electrons are organized into shells or energy levels around the nucleus.

Each energy level has a maximum number of electrons it can contain. The lowest energy level is always filled first and can only hold two electrons, while the levels. After this it can contain a maximum of eight electrons, the number of electrons in the outer shell of an atom determines which group the element belongs to in the periodic table and elements in the same group have similar reactivities