Chemical Bonds (Covalent and Polar and Non-Polar Molecules)

Chemical Bonds (Ionic)

I. Kinds of Bonds: A. Three types of chemical bonds you need to know 1. Ionic Bonds 2. Covalent Bonds 3. Metallic Bonds – Next Unit

A. Ionic Bonds: is the force of attraction between the opposite charges of the ions in an ionic compound

1. What is an ion and an ionic compound? a. Ion – Positively or negatively charged atom b. Ionic Compound – compounds made up of 2 or more ions

c. How does an atom become an ion? - An atom is considered electrically neutral if it has the same number of electrons as protons. If for any reason the atom loses or gains electrons the atom will have a charge because the negative charge of the electrons will be different than the positive charge of the protons

- Example: Magnesium 12 electrons and 12 protons (+ 12 protons) + (– 12 electrons) = 0 or No Charge

If magnesium gained 2 electrons then: (+12 protons) + (-14 electrons) = -2 or – Charge

d. How does an ionic bond form: - an ionic bond forms when oppositely charged atoms combine and there is a transfer of electrons

- Example NaCl: - Na has one electron in its valence shell and wants to get rid of it - Cl has 7 valence electrons and needs one - By Na transferring its one electron to Cl, - Na now has a complete valence shell; and by Cl gaining one it also has a complete shell.

- Ionic compound/bonds generally form between a metal and non-metal.

Chemical Bonds (Covalent Bonds and Polar and Non-Polar Molecules)

A. Covelant Bonds: 1. Definition: The attraction that forms between atoms when they share electrons, rather than losing or gaining electrons

2. Most atoms become stable by sharing electrons

a. Example: Cl2 Is this ionic or covalent, and how can you tell? - Answer: Covalent because there is no charge

- Explanation: Each chlorine atom has 7 electrons in its valence shell meaning they each only need 1 electron to have a full set. However each chlorine atom can’t give up one. So instead they will share an electron to give each the full set of 8 electrons

b. Generally formed between non-metals, and non-metals and metalloids

B. Polar and Non-Polar Molecules 1. Atoms in molecules do not always share electrons equally a. Electrons shared in a molecule may be more attracted to one atom than the other - Example: HCl The chlorine atom has a stronger attraction for electrons than hydrogen atoms do. So this means the electrons will spend more time near the chlorine atom than the hydrogen atom.

b. The uneven sharing gives the atoms in the molecule a slight but opposite charge from one another - In terms of HCl the chlorine atom has a slight negative charge and the hydrogen a slight positive charge.

- When this occurs it is considered a Polar Molecule Defined: A molecule that has a positive end and a negative End c. What happens when the atoms in a molecule share evenly? - Example: N2 Neither nitrogen atom has a greater attraction for electrons so the electrons will be shared evenly

- This causes the molecule not to have oppositely charged ends

- When this occurs it is considered a Non-Polar Molecule Defined: A molecule that does not have oppositely charged ends