Journal

•When you think of bonding what comes to mind?

•Why is bonding so important?

Electrons and bonding

Chpt 2 Part 2

Atomic Particles - Review

•Protons

+ charge, 1 Dalton mass

•Neutrons

no charge, 1 Dalton mass

•Electrons

- charge, essentially no mass

Electrons

• Electrons are the only particles that are involved in bonding.

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Some Atoms are Sociable, Others Aren’t Atoms “want” (are most stable) to have a filled outer electron shell

All atoms strive for a full outer shell of 8 electrons

Electron Shells

•The three dimensional space where an electron is found 90% of the time.

•The first shell can hold 2 electrons.

•The second shell can hold 8 electrons

Chemical Behavior Of An Atom

•Is determined by its electron configuration in the energy levels

Valence Electrons

•The electrons in the outermost energy level.•Electrons available for chemical bonds•Number of electrons they can receive or give for a full outer shell

Octet Rule

•The most stable condition is to have an outer level of 8 electrons.•Exception - 1st level is stable with only 2 electrons.•Every other shell 8•When stable - no chemical reactions will take place. Ex: Ne, He, (Noble gases)

Electrons of the first elements

Chemical Bonds

•Forces that join atoms together to form molecules.

•Electrons may be gained, lost, or

shared when 2 atoms are bonding.

Marriage

Divorce

Forming of a bond is like marriage

•More stable

•exothermic

The breaking of a bond relates to a divorce.

•Less stable

•Endothermic

Types of bonds

• Non metals bonded with non metals form Covalent Bonds.

• Metals bonded with non metals form Ionic bonds.

• Hydrogen bond

Charges

• An atom that gains one or more electrons will a negative charge.

• An atom that loses one or more electrons will a positive charge.

• Why?• An atom that gains or loses one or more

electrons is call an ion.• Positive ion is call a Cation. Negative ion is

called an anion.

Ionic Bonds•What is an Ionic Bond?

-An Ionic Bond is a chemical bond resulting from the TRANSFER of electrons from one bonding atom to another

-Each atom is left with a full outer shell.- An ionic bond is formed when a cation (positive ion) transfers electrons to an anion (negative ion). Metal and nonmetal

What are some characteristics of an ionic bond?

1. Crystalline at room temperatures

2. Have higher melting points and boiling points compared to covalent compounds

3. Conduct electrical current in molten or solution state but not in the solid state

4. Polar bonds

Pairing for the Greater GoodWhen atoms come together by sharing electrons the bond is a

covalent bond.

A molecule is formed when two or more atoms are bound together covalently

Covalent Bonds•What is an Covalent Bond?

-A covalent bond is a chemical bond resulting from SHARING of electrons between 2 bonding atoms.

-Each atom is left with a full outer shell.•

- A covalent bond is formed between two nonmetals.

What are some characteristics of a covalent bond?

1. Covalent bonds have definite and predicable shapes.

2. Very strong

3. Low melting and boiling points

Covalent Bonds can have multiple bonds, so you should be familiar with the following…

Single Covalent Bond- chemical bond resulting from sharing of an electron pair between two atoms.

Double Covalent Bond- chemical bond resulting from sharing of two electron pairs between two atoms.

Triple Covalent Bond-chemical bond resulting from sharing of three electron pairs between two atoms.

Relative Bond Strengths

CovalentStrongest

Ionic HydrogenWeakest

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Hydrogen Bonding

Molecules are joined together by weak hydrogen bonds.

The result is a hydrogen bond.

Each hydrogen Bone can be easily formed and easily broken.