Where are electrons found? Heisenberg uncertainty principle : It is impossible to know both the momentum and the position of a particle with certainty. However, we can use the Schrodinger equation to estimate where an electron is likely to be found. The Schrodinger equation is given above. It is third year college Chemistry, you do not need to know anything about it, except that it exists.

The schroedinger equation describes the orbitals in which electrons are found. Quantum numbers are used to describe the position of electrons. N = the energy level L = the angular momentum (shape of orbitals) M = magnetic quantum number (orientation) S = spin quantum number (clockwise or counterclockwise)

Electrons fill lowest energy levels first. The s orbital is the simplest orbital. The 1s orbital is the lowest energy orbital. 2 s orbital is the second lowest energy orbital. Two electrons can fit in any orbital.

Once the lowest energy level is filled, the next energy level begins to fill. The second lowest energy type of orbital are “p” orbitals. Each p orbital holds two electrons. 3 sets of two electrons is a total of 6 electrons.

d-orbitals are more complex. There are no 1d or 2d orbitals. d orbitals do not begin to get filled until after the 4s orbital is filled. There are five sets of d orbitals, two electrons each for a total of 10 electrons in the d orbitals.

f orbitals are only used for elements in period 6 and 7 There are seven types of orbitals, two electrons each.

Electrons fill orbitals one at a time, beginning at 1s and increasing energy until all the electrons have a unique spot. H = 1s 1 Hydrogen has one proton, one electron. The Aufbau Principle: Electrons fill the lowest energy levels first

Electrons fill orbitals one at a time, beginning at 1s and increasing energy until all the electrons have a unique spot. He = 1s 2 Helium has two protons, two electrons. The Aufbau Principle: Electrons fill the lowest energy levels first

Electrons fill orbitals one at a time, beginning at 1s and increasing energy until all the electrons have a unique spot. Li = 1s 2 2s 1 Lithium has three protons, three electrons. One less electron and lithium has a full set of electrons we can predict that lithium will be very reactive. And in fact, lithium reacts with water to produce a gorgeous red flame! The Aufbau Principle: Electrons fill the lowest energy levels first

Electrons fill orbitals one at a time, beginning at 1s and increasing energy until all the electrons have a unique spot. Be = 1s 2 2s 2 Beryllium has four protons, four electrons. The Aufbau Principle: Electrons fill the lowest energy levels first

Electrons fill orbitals one at a time, beginning at 1s and increasing energy until all the electrons have a unique spot. B = 1s 2 2s 2 2p 1 boron has five protons, five electrons. The Aufbau Principle: Electrons fill the lowest energy levels first

Electrons fill orbitals one at a time, beginning at 1s and increasing energy until all the electrons have a unique spot. C = 1s 2 2s 2 2p 2 Carbon has six protons, six electrons. Hund’s Rule: One electron in each orbital before two electrons In any orbital. The Aufbau Principle: Electrons fill the lowest energy levels first

Electrons fill orbitals one at a time, beginning at 1s and increasing energy until all the electrons have a unique spot. N = 1s 2 2s 2 2p 3 Nitrogen has seven protons, seven electrons. Hund’s Rule: One electron in each orbital before two electrons In any orbital. The Aufbau Principle: Electrons fill the lowest energy levels first

Electrons fill orbitals one at a time, beginning at 1s and increasing energy until all the electrons have a unique spot. O = 1s 2 2s 2 2p 4 Oxygen has eight protons, eight electrons. Hund’s Rule: One electron in each orbital before two electrons In any orbital. The Aufbau Principle: Electrons fill the lowest energy levels first

Electrons fill orbitals one at a time, beginning at 1s and increasing energy until all the electrons have a unique spot. F = 1s 2 2s 2 2p 5 Fluorine has nine protons, nine electrons. Hund’s Rule: One electron in each orbital before two electrons In any orbital. One more electron and fluorine has a full set of electrons we can predict that fluorine will be very reactive. The Aufbau Principle: Electrons fill the lowest energy levels first

Electrons fill orbitals one at a time, beginning at 1s and increasing energy until all the electrons have a unique spot. Ne = 1s 2 2s 2 2p 6 Neon has ten protons, ten electrons. Hund’s Rule: One electron in each orbital before two electrons In any orbital. Neon is a noble gas, it tends not to react. We saw its spectrum was a gorgeous red, with green and yellow. It is used for lights BECAUSE it doesn’t react. The Aufbau Principle: Electrons fill the lowest energy levels first

Electrons fill orbitals one at a time, beginning at 1s and increasing energy until all the electrons have a unique spot. Na = 1s 2 2s 2 2p 6 3s 1 Sodium has eleven protons, eleven electrons. Hund’s Rule: One electron in each orbital before two electrons In any orbital. One less electron and sodium has a full set of electrons we can predict that sodium will be very reactive. If you remember the flame test, you will remember that sodium had a yellow-orange flame. When you put sodium in water, it catches fire and gives a bright yellow flame. The Aufbau Principle: Electrons fill the lowest energy levels first

Electrons fill orbitals one at a time, beginning at 1s and increasing energy until all the electrons have a unique spot. K = 1s 2 2s 2 2p 6 3s 2 3p 6 4s 1 Lets skip to potassium, atomic number 19 Hund’s Rule: One electron in each orbital before two electrons In any orbital. One less electron and potassium has a full set of electrons we can predict that potassium will be very reactive. If you remember the flame test, you will remember that potassium had a violet flame. When you put potassium in water, it catches fire and gives a violet flame. The Aufbau Principle: Electrons fill the lowest energy levels first

Electrons fill orbitals one at a time, beginning at 1s and increasing energy until all the electrons have a unique spot. Lets skip to chromium, atomic number 24 Cr = 1s 2 2s 2 2p 6 3s 2 3p 6 4s 2 3d 4 Hund’s Rule: One electron in each orbital before two electrons In any orbital. The Aufbau Principle: Electrons fill the lowest energy levels first If we move an electron from 4s to 3d, we get a symmetrical electron configuration. This is energetically favored. Cr = 1s 2 2s 2 2p 6 3s 2 3p 6 4s 1 3d 5