CHEMISTRYCHAPTER 6Ionic and Metallic Bonding

Covalent Bonding

CHEMICAL BONDS

• A Chemical bond is a force that holds two or more atoms together.

• Chemical bonds involve (use) the valence electrons in the atoms.

BONDS, CHEMICAL BONDS

ELEMENTS IN A GROUP

•Behave similarly b/c they contain the same number of valence electrons

•Valence electrons are electrons in the highest occupied energy level

•Valence electrons determine an atom’s chemical properties

VALENCE ELECTRONS

• Valence electrons of a representative element = group number

• Group 1A = 1 valence electron

• Group 4A (carbon) = 4 valence e- Group 5A (nitrogen) = 5 valence e-

• Group 6A (oxygen) = 6 valence e-

• Noble gases (group 8A) = 8 valence

• EXCEPT FOR HELIUM = 2 valence e-

ELECTRONS IN CHEMICAL BONDS

•Are the valence electrons

•Electron dot structures are diagrams that show the valence electrons as dots around the symbol

LEWIS STRUCTURES1) Find your element on the periodic table.

2) Determine the number of valence electrons.

3) This is how many electrons you will draw.

LEWIS STRUCTURES

• Find out which group (column) your element is in.

• This will tell you the number of valence electrons your element has.

• You will only draw the valence electrons.

GROUPS -REVIEW

•Each column is called a “group”

•Each element in a group has the same number of electrons in their outer orbital, also known as “shells”.

Group 1 = 1 electron

Group 2 = 2 electrons

Group 8 = 8 electrons

Except for He, it

has 2 electrons

•The electrons in

the outer shell are

called “valence

electrons”

LEWIS STRUCTURES1) Write the element

symbol.

2) Carbon is in the 4th

group, so it has 4 valence electrons.

3) Starting at the right, draw 4 electrons, or dots, counter-clockwise around the element symbol.

LEWIS STRUCTURES1) Check your work.

2) Using your periodic table, check that Carbon is in the 4th

group.

3) You should have 4 total electrons, or dots, drawn in for Carbon.

LEWIS STRUCTURESOn your worksheet, try these elements on your own:

a) H

b) P

c) Ca

d) Ar

e) Cl

f) Al

LEWIS STRUCTURESOn your worksheet, try these elements on your own:

a) H

b) P

c) Ca

d) Ar

e) Cl

f) Al

LEWIS STRUCTURESOn your worksheet, try these elements on your own:

a) H

b) P

c) Ca

d) Ar

e) Cl

f) Al

LEWIS STRUCTURESOn your worksheet, try these elements on your own:

a) H

b) P

c) Ca

d) Ar

e) Cl

f) Al

LEWIS STRUCTURESOn your worksheet, try these elements on your own:

a) H

b) P

c) Ca

d) Ar

e) Cl

f) Al

LEWIS STRUCTURESOn your worksheet, try these elements on your own:

a) H

b) P

c) Ca

d) Ar

e) Cl

f) Al

LEWIS STRUCTURESOn your worksheet, try these elements on your own:

a) H

b) P

c) Ca

d) Ar

e) Cl

f) Al

NOBLE GASES

•Unreactive in chemical reactions

•Octet rule: in forming compounds, atoms tend to achieve the electron configurations of a noble gas

• Metallic elements tend to LOSE valence electrons

• Leave a complete octet in the next lowest energy level

• Nonmetallic elements tend to gain or SHARE electrons with another nonmetallic element to achieve a complete octet

• Atoms are electrically neutral b/c the # of protons = # of electrons

• An ion forms as an atom or group of atoms loses or gains electrons

• A cation is a positive ion formed by the LOSS of valence electrons

• Name a cation the same as the atom (just add “ion”)

CATIONS

• Differ chemically from their atoms

• Na atom explosive with water

• Na+ ion in NaClunreactive and harmless

• K atom explosive with water

• K+ ion in bananas harmless

CATIONS

• Loses one valence electron to become a positively charged sodium ion (Na+ )

•Now, sodium has an electron configuration like neon

•Magnesium has 2 valence electrons

• LOSES 2 electrons to have a +2

FORMATION OF POSITIVE IONS

• Lose one or more electrons

TRANSITION METALS

• ALWAYS LOSE ELECTRONS TO FORM CATIONS

• Number of electrons lost can vary

• Ex: Iron (Fe) can lose 2 or 3 e-

• Fe+2 or Fe+3

• Transition metals can sometimes form pseudo-noble gas configurations• Silver (Ag) would have to lose 11 or gain 7 electrons. Instead, loses

it’s one 5s

• Then has 18e in outer most energy level

ANIONS

•An atom or group of atoms with a negative charge. Atom must GAIN electrons to become negative.

• The name of the anion usually ends in “-ide”

•Chlorine (Cl) Chloride (Cl-)

•Oxygen (O) Oxide (O-2)

ANIONS

• Easier for nonmetals to gain electrons vs. losing them b/c they have relatively full valence shells

• Halide ions: ions produced when halogens (like chlorine, fluorine) gain one electron

• All halide ions have a charge of -1

• Oxygen forms ions by gaining 2 electrons (O-2)

FORMATION OF NEGATIVE IONS