Atoms make bonds with other atoms to form molecules. The number of bonds that an atom of an element makes with other atoms is the valence of that element.
The first row of the periodic table contains two elements, hydrogen and helium. Hydrogen has a valence of one. Helium has a valence of zero.
The second row of the periodic table contains eight elements. The valences of these eight elements are:
1, 2, 3, 4, 3, 2, 1, 0
Carbon is element 6. Carbon has a valence of 4. A carbon-12 atom is made up of six deutons. A carbon-12 atom is a helium-4 atom surrounded by four deutons. The four deutons are located at the vertices of a tetrahedron. Each of these four deutons makes one bond with another atom.
Nitrogen is element 7. Nitrogen has a valence of 3. A nitrogen-14 atom is made up of seven deutons. A nitrogen-14 atom is a helium-4 atom surrounded by three single deutons and a pair of deutons. The three single deutons each make one bond with another atom.