The Structured Atom Model postulates that atoms are built in a tree-like fashion from clusters of protons. When we first started talking about SAM we needed a name for these clusters and came up with the word 'nuclet'.
A nuclet is a densely packed geometrically arranged cluster of protons that combine together with other nuclets to create the nucleus of the atom.
The nuclets are named after the element where they first appear. This naming convention is similar to how we name the groups or columns of the periodic table. For example carbon is the first element in the 14th column so we call that column the "Carbon group".
Nuclets can be divided into 3 categories - building blocks, building phase, capping phase.
The 8 elements in the second row of the periodic table - Lithium, Beryllium, Boron, Nitrogen, Oxygen. Fluorine and Neon - are each composed of a single Nuclet in various stages of growth. This growth pattern results in the valence pattern of 8 ---- +1, +2, +3, +/-4, -3, -2, -1, 0. Neon, the last element in the row is inert because the nuclet is complete.
The 8 elements of the third row of the periodic table - Sodium through Argon - start and complete the growth of the second nuclet. The last element in the row, Argon, is inert because it consists of two completed nuclets.
The 18 elements of the fourth row of the periodic table - Potassium through Krypton - are more complex because as the atom branches it creates more possibilities for where the atom can grow. This is the reason there are a large number of transition metals. The last element, Krypton, is inert because it is the completion of 5 nuclets.
Deuterium and Helium are thought to be the basic building blocks of atoms. When a deuterium is added to an existing atom it will always form a tetrahedron with two protons (another deuterium) that are already in the nucleus.
Deuterium - 2 protons - 1 inner electron
The deuterium atom is the most basic building block. Unlike a free 'neutron' it can exist by itself as it is stable. Within the atom it always combines with 2 additional protons to complete a tetrahedron.
Helium - Tetrahedron
Helium - 4 protons - 2 inner electrons
The tetrahedron is the first platonic solid. It is densely packed which means all faces are triangular and the protons are as close together as possible. The tetrahedron is found throughout the nucleus. Anytime a proton is added to the nucleus it must form a tetrahedron with protons already in the nucleus.
The helium nucleus is also called the alpha particle and is known to be the product of alpha decay.
The smallest nuclet is the lithium nucleus and has 1 ring of five protons with 1 or 2 protons in the center of the ring. The next two stages are the beryllium and boron nuclets which are intermediate steps and are really intertwined lithium nuclets. The shape transforms with carbon into an icosahedron, one of the 5 platonic solids. The growth of a nuclet from the lithium state to carbon is called the building phase.
Lithium - Pentagonal Bi-Pyramid
Lithium - 7 protons - 4 inner electrons
Lithium is the first solid element. It has one ring of 5 protons which give it a valence of 1.
Lithium 7 is the preferred isotope with 92.4% abundance. Lithium 6 is 7.6% abundant and is the same structure shown except 1 proton is missing and is an incomplete structure.
Beryllium - 9 protons - 5 inner electrons
Beryllium is essentially 2 lithium nuclets that are intertwined which gives it a valence of 1 or 2.
Boron - 11 protons - 6 inner electrons
Boron is essentially 3 intertwined lithium nuclets which give it a valence of 3.
Nature prefers Boron 11 (80%) over Boron 10 (20%). This is because the Boron 11 is a more balanced structure.
Carbon 12 - Icosahedron
Carbon - 12 protons - 6 inner electrons
Carbon is a perfect icosahedron which is one of the five platonic solids. It can be thought of as 12 intertwining rings of 5 protons which implies rotation. However close analysis shows only 4 rings can be active at any time without collisions between the rings. This is thought to be why carbon has a valence of +4/+2/-4.
Now that a perfect icosahedron has been created with carbon it has to be broken to continue building. As protons are added the icosahedron is distorted slightly as the new protons form small tetrahedrons that dominate the structure. These new protons cap the valence rings formed in the building phase. Once all valence rings are capped the nuclet is said to have a neutral ending. This means it is no longer chemically reactive. The first time time this happens is with the element neon.
Adding two protons forms (green) a tetrahedron with the protons already in the nucleus. This tetrahedron distorts the icosahedron a little and a gap opens in the top of the icosahedron. The new tetrahedron caps one of the four valence rings.
Adding four protons caps both valence rings on one side of the atom. This makes that side of the atom chemically non-reactive or neutral.
The preferred isotope for fluorine has three additional protons instead of two. It is theorized the additional proton is required to balance the nucleus. The new protons cap another valence ring.
Neon - Neutral Ending - Backbone Nuclet
Neon is when all four of the valence rings have been capped. This is what makes neon an inert or noble gas. We also call this a neutral ending.
This structure is also called the backbone. It is the primary building block of larger atoms. These are combined together in a tree-like fashion with this structure making the spine of the atom. Only the endings of the branches are different.