Atoms consist of protons and neutrons in the nucleus, surrounded by electrons that reside in orbitals. Orbitals are classified according to the four quantum numbers that represent any one particular orbital's energy, shape, orientation, and the spin of the occupying electron. The first section of this SparkNote on Atomic Structure will focus on the electron and the mechanism of describing electrons and their orbitals.

As we shall see in the second section, electrons fill up orbitals in a systematic fashion, following the rules of the Aufbau principle. The configuration of electrons in an atom play a vital role in chemistry. Virtually every chemical process relies on the interactions of electrons between atoms, most particularly on the tendency of atoms to follow the octet rule, the tendency to gain a full valence shell electrons. In the second section of this SparkNote, we will discuss the properties of electrons, distinguishing between valence electrons and inner electrons, then broadening the discussion into an examination of the properties of electron conifgurations.

Unsurprisingly, given the importance electron configurations play in determining the chemical and physical characteristics of an atom, atoms with similar electron configurations also display similar characteristics. In other words, much of the periodicity of the Periodic Table arises from electron configuration. To see the periodic table, click here. Once the window appears, roll your mouse over the elements to see their specific information. You can also access the periodic table by going into the SparkNotes reference section that resides at the top of every SparkNotes page. We discussed a number of periodic trends in the SparkNote on the Periodic Table table. In the third section we will quickly discuss those previous trends again, and then move to a description of the periodic trends relating to atomic size, ionization energy, electron affinity, and electronegativity.