The nucleus is very small in comparison to the volume of the atom.
Electrons occupy most of the volume of the atom.
Rolling your mouse over the image shows an expanded view of the nucleus.
Electrons occupy most of the volume of the atom.
Rolling your mouse over the image shows an expanded view of the nucleus.
When chemical reactions occur, it is the electrons that are involved. Various experiments have been done to discover more about the detailed arrangement of electrons in the atom. It has been found that the chemical properties of an element can be understood in terms of the arrangement of the electrons around the nucleus.
The model of electron arrangement that is consistent with experimental data has electrons in specific (discrete) energy states known as energy levels. These are also referred to as shells.
The electrons on atoms of the first twenty elements in the periodic table may occupy up to four energy levels (shells). The shells (energy levels) closer to the nucleus are occupied first.
How do you know how many electrons are available on an atom?
One way to represent the different possible energy levels (shells) of the electrons is to show them in rings around the nucleus as in the diagram.
It is important to appreciate that these represent energy levels (shells), not paths!!
It is important to appreciate that these represent energy levels (shells), not paths!!
The electrons on atoms of the first twenty elements in the periodic table may occupy up to four energy levels (shells). The shells (energy levels) closer to the nucleus are occupied first.
The number of energy levels (shells) occupied depends on how many electrons are available.
The diagram shows that two energy levels (shells) are occupied for beryllium, an atom that has four electrons.
The diagram shows that two energy levels (shells) are occupied for beryllium, an atom that has four electrons.
The number of electrons on any atom is equal to its atomic number in the periodic table.
This is equal to the number of protons and the number of electrons on an atom because atoms are electrically neutral.
This is equal to the number of protons and the number of electrons on an atom because atoms are electrically neutral.
Helium has two electrons because the atomic number of helium is 2.