Periodic Table Shortcut Noble Gas Notation Lewis Dot

Periodic Table Shortcut Noble Gas Notation Lewis Dot Structures

When we write electron configurations, do we need to always start at the beginning? No, there a few shortcuts.

The first shortcut involves the placements of element’s on the periodic table l l Let us look at the electron configurations from yesterday’s homework and bell work from today and see how they fall on the periodic table. You will need 4 color pencils for this.

So, the periodic table is arranged with electron configurations in mind The only exception is He

The rows and columns l The rows correspond to the principle quantum number (n) l l l In other words, each time you drop a row on the periodic table, you go out an energy level. Be careful with the d and f areas The d area is n-1 and the f area is n-2 La and Ac are considered the first f area elements The sets of columns correspond to l quantum numbers and the amount of electrons in that orbital

So, by looking at the periodic table, one can find an element’s electron configuration

Let’s try some examples: Remember it should be a number then a letter then a superscript l l What is the last orbital of tin (Sn)? What is the last orbital of Ruthenium (Ru)? What is the last orbital of Holmium (Ho)? What element ends with the electron configuration of: l l l 5 s 1 6 p 4 5 f 3 (remember Ac is first f)

The second shortcut l l We need to find a group of elements that have completed or full orbitals. That group is the noble gases. The last column on the periodic table. This group can be used to write an abbreviated version of an element’s electron configuration.

Let’s look at yesterday’s homework again

How to write Noble Gas Notation l l l Find the closest _____ noble gas to the element in atomic number without going over. Write that noble gas’s symbol in brackets. Go back to the beginning of the row and work back to the elements writing down the orbital sections and counting the electrons as you go.

Examples l l l As (Atomic Number – 33) What is the closest Noble gas without going over? Ar So, [Ar] 4 s 2 3 d 10 4 p 3 C l [He]2 s 22 p 2 Pb l [Xe] 6 s 2 4 f 14 5 d 10 6 p 2

Lewis Dot Formulas l l Shows the valence electrons of an atom Valence electrons are the electrons in the outermost energy level The only electrons that are in the outermost energy level are s and p. Therefore, the most valence electrons an atom can have is 8 (2 from the s and 6 from the p).

Lewis Dot Formulas l l l So, Lewis Dot Formulas are the chemical symbol surrounded by dots. There will be one dot per electron in the s and p orbital Hund’s rule must be followed

What is the Lewis Dot Structure for the following? l l l Francium Arsenic Hydrogen Krypton Oxygen