CHEMICAL BONDING the combining of atoms of elements to form new substances (compounds; two or more elements combined) Chemical bonding depends on the arrangement of an atom's outer shell electrons

Why do atoms combine with other atoms?

The Octet Rule All elements want to be like the Noble Gases and have 8 electrons in their outer shell. They will steal, borrow, or share electrons from other atoms to make this happen. The magic number is 8

Two types of Bonds (we will also be looking at metalic bonds) Ionic: When electrons are transferred from one atom to another (metals- non metals) Covalent: When atoms share one or more electrons.

Ionic Bonds A bond between a metal and nonmetal

How does an Ionic Bond Work? Always between a metal and nonmetal. Atoms want a full outer shell, but they are lazy. They will do whatever is easiest. Metals give away electrons to have a full outer shell. Nonmetals steal electrons to have a full outer shell.

What is the end result? IONS – atoms that have a charge. When they lose or gain an electron, they are no longer neutral. Since opposite attract, the charged ions will combine.

Oxidation Number –helps us remember what charge the ion has. The number of electrons that an atom will lose or gain AND the charge. EXAMPLE: Aluminum has 3 valence electrons. It will lose those 3 to have a full outer shell. Since it lost electrons, it will now have a positive charge. Al +3

Remember! Atoms are lazy! They will do whatever is easiest to get a full outer shell. Less than 4 valence electrons: will give away electrons in their outer shell. More than 4 valence electrons: will steal electrons from another atom. Exactly 4 valence electrons: they are to lazy to lose or steal so they usually share electrons. (This is called a covalent bond)

What is an ionic bond? Atoms will transfer one or more ________________ to another to form the bond. Each atom is left with a ________________ outer shell. An ionic bond forms between a ___________ ion with a positive charge and a ________________ ion with a negative charge. Example B1: Sodium + ChlorineExample B2: Magnesium + Iodine ELECTRONS COMPLETE METAL NONMETAL

Answer these questions: An atom that gains one or more electrons will have a ____________________ charge. An atom that loses one or more electrons will have a ____________________ charge. An atom that gains or loses one or more electrons is called an ____________. A positive ion is called a ______________ and a negative ion is called an _______________. POSITIVE NEGATIVE ION CATION ANION “An-Eye-On” “Cat-Eye-On”

But wait…. Ions combine because opposite charges attract, BUT the resulting compound is neutral.

So now that the compound is neutral it must be written that way. People do this by balancing out the charges.

If the oxidation numbers already equal zero… You are lucky! Just write the abbreviations for the elements and that is the chemical formula EXAMPLE: NA +1 Cl -1Mg +2 O -2 Formula: NaClFormula: MgO

If the oxidation numbers don’t equal zero… Criss-Cross Method Count the atoms Method