Energy Levels and Electronic Configuration Chemistry the virtual school

in a previous video we let the other Nikolas is at the center of an atom and that's this made up of protons and neutrons and around the central point we find the electrons we also know that in a neutral atom in number of electrons always equals the number of protons so in a neutral atom of carbon there are six protons which mean there must be six electrons the electrons in the atom are organized around the nucleus in different

energy

levels

or shells shells can only hold a certain amount of

electrons the first and innermost shell can only hold a maximum of two electrons the shells that come out of this can hold a maximum of eight electrons let's look at some Arrangements lithium has three protons therefore it has three electrons the first three electrons are placed in the first shell closest to the nucleus and the third electron is placed in the second shell two plus one three electrons these diagrams are called dot and cross diagrams and they 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

electronic

configuration

in a written form the lithium this will be written as a lie to one in the diagram the nucleus is represented by the element symbol or essential 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 cell and the next four a place in the second shell 2+4 6 electrons this would be written as c2 for 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 plus 8 plus 2 12 electrons this would be written as mg 2 8 2 the organization of these

energy

levels

is what gives elements at different reactivities the number of

electrons in the outer shell of an atom tells you the group number to which they belong on the periodic table members of the same group with same number electrons in the outer shell have similar activities so electrons are arranged in shells or

energy

levels

around the nucleus each

energy

level has a maximum number electrons it can hold the lowest

energy

level has always fell first you can only hold two electrons while their

levels

out of this can hold a maximum of 8 electrons the number of

electrons in the outer shell of an atom determines which people the element belongs to on the periodic table and elements in the same group have similar reactivities