District 3 - Chemical Bonding

Welcome to your training for how to take down District 3 when you are in the arena. The elements of District 1 and 2 have nothing on these guys. This is the place where all the elements are combined, broken apart, and recombined in an infinite number of arrangements. From this District, we get all the compounds that exist within our known universe. They are advised by past champion (and man who is on constant suicide watch) Gilbert Lewis. You will need to be beware of District 3's ability to mix elements together to make a nasty compound that will do terrible (and likely irreversible) damage to you.

Past District 3 Champions

  • He may be a champion of the chemistry hunger games, but he'll forever be known for his lack of nobel prizes.

Ionic Bonding

Please take out your District 3 guided notes and watch the lesson below:

Electrons are often transferred between elements so that both of them are able to complete their octet. An element that wants to get rid of electrons gives away its electrons to an element that wants to gain electrons to complete its octet. This transfer of electrons causes an ionic bond to form.

Metals typically donate or give away their electrons in order to achieve a full outer valence. Non-metals typically accept electrons in order to achieve a full outer valence. This exchange of electrons leads to an ionic bond. Ionic Bond – A bond that forms between an anion and cation as a result of the elements exchanging electrons.

A monoatomic ionic bond is a bond that forms between 1 positive element and 1 negative element. Typically a bond between a metal and a non-metal. These elements bond to form a compound. A compound is any substance made of atoms of two or more different elements joined by a chemical bond. This compound does not have a charge because ions combine in order to create a final charge of 0.

To determine the chemical formula for an ionic compound you can follow the following steps:

  1. Write down the two ions with the positive ion written first.
  2. Circle the two charges that are listed as superscripts.
  3. Draw an arrow diagonally so that the charge of one ion becomes the subscript of another ion.
  4. Remove the negative sign from the negative charge.
  5. Push the elements together so that it is written as one compound.
  6. If a 1 is written, simplify by removing the 1..

Polyatomic ions are a charged ion composed of two or more elements that can be considered as acting as a single unit. They are made of two or more elements and both elements are non-metals. Since these are ions, they can form ionic bonds with other monoatomic or polyatomic ions.

  1. Place the monoatomic ion and polyatomic ion next to one another making sure that the positively charge ion is first.
  2. Place parentheses around the polyatomic ion.
  3. The charge is brought down in the same way as previously shown. The number is placed outside the parenthesis.
  4. Remove negative sign.
  5. Double check that the charges add up to zero!

Crystal Lattices

Ionic compounds have a positive and negative charge and this charge causes salt crystals or crystal lattices to form. Salt crystals that we see are repeating structures of a very simple unit. Arranged so that there is a repeating structure of positive and negative charges.

Crystal lattices have a structure of repeating positive and negative charges Positive charged ions in an ionic compound are attracted to other negative charged ions. This attraction between positive and negative charges holds crystal lattices together. This attraction between positive and negative charged ions is known as electrostatic attraction.

Metallic Bonds

What allows metals to conduct electricity so easily is the fact that the atoms essentially exist in a "sea of electrons" where electrons roam freely between individual atoms. This mix of positive metal ions and electrons contributes to much of the characteristics of metals.

This sea of electrons essentially acts as the "glue" that holds the metal cations together. Though some metals are also capable of exhibiting covalent bonds, understanding the coulombic force that holds metals together in metallic lattices is the most important part here.

Covalent Compounds and Lewis Structures

Covalent bonds are a bond between two or more non-metals. In a covalent bond, the electrons are shared between the elements so that each can achieve a full outer valence shell.

Most molecules in biology are covalent compounds. Things such as proteins, carbohydrates, and DNA all are held together by the sharing of electrons.

Identifying ionic and covalent compounds can be done by examining the elements that make up the compound. If it is made of a metal and a non-metal, then it is an ionic compound. If it is made of two or more non-metals, then it is a covalent compound.

Lewis Dot structures for an element are like Bohr diagrams, but they only show the valence electrons. The group number (Group 1A, 2A, etc.) tells us the number of valence electrons for elements.

The steps to draw a Lewis structure for an element are as follows:

  1. Write the element symbol down
  2. Determine the number of valence electrons that your element has.
  3. Starting at the top of the element write one dot to represent each valence electron (i.e. 1 valence electron = 1 dot)
  4. Start at the 12 o’clock position and place one dot, then go to the 3 o’clock position and place another dot, then go to the 6 o’clock position and place another dot, and, finally, go to the 9 o’clock position and place another dot.
  5. If you still have valence electrons, then repeat step 4 until you run out of electrons. Draw these dots as pairs. In the end, you should have as many dots as you have valence electrons.

Identifying ionic and covalent compounds can be done by examining the elements that make up the compound. If it is made of a metal and a non-metal, then it is an ionic compound. If it is made of two or more non-metals, then it is a covalent compound.

We can indicate electrons being shared in a covalent compound using Lewis structures. Electrons that participate in electron sharing are unpaired electrons. Unpaired electrons are those that only have 1 electron at the 12, 3, 6, or 9 o’clock position on Lewis structure.

When drawing Lewis structures there are a few guiding rules to help you draw the correct molecule:

  • Halogens and hydrogen usually form only one bond and usually are located at the end of a molecule.
  • The central atom is always carbon (if it is present) and/or the element that has the lowest electronegativity.

When elements share two electrons this is known as single covalent bond. Elements can share more then one set of electrons. They can also form double and triple bonds. A single bond = 2 electrons, a double bond = 4 electrons, and triple bond = 6 electrons.


Foiling Gilbert Lewis' Plan

As you begin to eat the small amount of food you have found, you smell a hint of almond and drop the food. You realize that this is the doing of District 3 and their master chemist Gilbert Lewis. In order to ensure that you can use this trick to kill District 3, complete the following problems: SEE ASTOR FOR DISTRICT 3 ASSESSMENT!

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