The Periodic Table 3 – Bohr Diagrams

Lesson 11October 19th, 2010

Patterns in the Arrangements of Electrons

• A very important pattern in the arrangement of electrons is that elements in the same group have the same number of valence electrons.

Patterns in the Arrangements of Electrons

• Group 1: Atoms of hydrogen, lithium, and sodium each have one valence electron. These elements share some chemical properties with them because of their similar valence electron arrangements. They all form ions with a 1+ charge.

Patterns in the Arrangements of Electrons

• Group 18: Nobles gases have their valence shell completely filled with the maximum number of electrons that they can hold. • The noble gases share many properties because

their atoms all have filled valence shells, this makes them very stable.

Patterns in the Arrangements of Electrons

• The number of valence electrons is not only related to the physical properties of a group of elements. The number of valence electrons is also related to the ways in which atoms of elements combine to form compound

Organizing the Periodic Table in Different Ways

Scientists continue to organize the elements in different ways.

• Dr. Theodor Benfey, a U.S. chemist, suggested a spiral version of the periodic table. • In Dr. Benfey’s periodic table, the elements are

shown in an unbroken series, starting with hydrogen and radiating outward.

Organizing the Periodic Table in Different Ways

• Another periodic table is known as the physicist’s periodic table. This periodic table is three-dimensional and groups the elements according to the energy levels of their electrons. – It has been turned sideways to fit on the page

Bohr Diagrams

• To represent electron arrangements at various orbits we use Bohr diagrams. Each orbit has a set number of electrons.

Orbit # # of Electrons1 22 83 84 18

• Every row in the period contains a shell. The farther you move down the table the more shells you added to the diagram. H = 1 shell, Li = 2 shells, K = 3 shells.

• Moving left to right on the periodic table adds valence electrons to the shells of that row. Na has 1 valence e-, Mg has 2 valence e-, Al has 3 valence e-, etc.

Drawing Bohr Diagrams

• Draw the Bohr diagram of Hydrogen• N = A – Z• N = • N =

Drawing Bohr Diagrams

• Draw the Bohr diagram of Helium • N = A – Z• N = • N =

Drawing Bohr Diagrams

• Draw the Bohr diagram of Lithium • N = A – Z• N = • N =

Drawing Bohr Diagrams

• Draw the Bohr diagram of Beryllium• N = A – Z• N = • N =

Drawing Bohr Diagrams

• Draw the Bohr diagram of Aluminum • N = A – Z• N = • N =

Drawing Bohr Diagrams

• Draw the Bohr diagram of Argon • N = A – Z• N = • N =

• Draw the Bohr diagrams for the first 20 elements. – Hand in