ChemistryChapter 1

Atomic Structure and Chemical Bonds

All matter, including solids like wood and steel, contains

mostly empty space.

Scientists are able to pinpoint the exact

location of an electron in an atom.

Electrons orbit a nucleus just like planets orbit the sun.

The number of electrons in a neutral atom is the same

as the atom’s atomic number.

Noble gases react easily with other elements.

All elements transfer the same number of electrons when bonding with other

elements.

Electrons in metals can move freely among all the ions in

the metal.

Some atoms bond by sharing electrons between the two

atoms.

Water molecules have two opposite ends like the

poles on a magnet.

1.1 Why Do Atoms Combine?

I. Atomic Structure

A. Atoms are mostly empty space

B. Nucleus contains protons and neutrons

C. Most of the volume is the electron cloud

D. Electrons

1. NOT so much like the planets circling

the sun

2. Planets do not have electrical charges

3. Planets move in predictable orbits

4. Cannot predict the exact position of an

electron

5. Use a mathematical formula that

predicts where it might be

E. Element Structure

1. Specific number of protons, neutrons

and electrons

2. Protons = electrons for a neutral atom

II. Electron Arrangement

A. Electron Energy

1. Some electrons closer to the nucleus

than others

2. Different areas where electrons are

located = energy levels

B. Number of Electrons

1. Each energy level can hold a max

number of electrons

2. Farther from the nucleus = more

electrons the energy level can hold

C. Energy Steps

1. Electrons closest to the nucleus have

lowest energy and hardest to

remove

2. Electrons farthest from nucleus have

highest energy and easiest to

remove

3. Formula: 2n^2 where n=energy level

III. The Periodic Table and Energy Levels

A. For neutral atoms, # of protons = # of

electrons

B. Determine the number of electrons from

atomic number

IV. Electron Configurations

A. Number of electrons increases from left to

right on Periodic Table

B. Atoms with full outer shells are stable

C. Atoms with incomplete outer shells are

unstable and will bond with other atoms

D. Elements in period 1: up to 2 electrons

E. Elements in following period: up to 8 electrons

V. Element Families (Groups)

A. Elements in the same family have similar

traits

B. Noble Gasses

1. Eight electrons in outer shell

2. Stable (don’t react/form bonds)

3. Trait allows for many uses

C. Halogens

1. Need to gain 1 electron to be stable.

2. Fluorine

a. Most reactive

b. Outer energy level closest to

nucleus.

3. Reactivity decreases down group

4. Outer energy levels are farther from

nucleus

D. Alkali Metals

1. One electron in outer energy level

2. Need to lose 1 electron to be stable

3. Reactivity increases down the group

4. Outer energy levels farther from

nucleus

5. Less energy needed to remove

electron farther from nucleus.

VI. Electron Dot Diagrams

A. Symbol for element surrounded by dots that

represent electrons in outer energy level

B. How to Write Them

1. Periodic table shows number of

electrons in outer energy level.

2. Write element symbol

3. Start at top left and work clockwise

by adding 1 dot to each side.

4. When more than 4, begin doubling up

C. Using Dot Diagrams (on board)

1.2 How Elements Bond

I. Ionic Bonds – Loss and Gain

A. Sodium

1. Had 1 electron in outer shell

2. Makes it highly unstable

3. Reacts violently with water

4. Loses electron: stable outer shell

B. Chlorine

1. Forms bonds the opposite way of sodium

2. Has 7 electrons in outer shell

3. Gains 1 electron to form stable octet

C. Ions – A Question of Balance

1. Losing electron unbalances sodium’s

charges

2. Becomes + charged

3. Chlorine becomes – charged

4. Ion: atom without a neutral

5. Become Na+ and Cl-

D. Bond Formation

1. + charge is attracted to – charge

2. Attraction = ionic bond

3. Sodium chloride = table salt

4. Compound: a pure substance

containing two or more elements

that are chemically bonded.

E. More Gains and Losses

1. Can elements gain/lose more than 1

electron?

2. Answer: yes!

3. Example: MgO and MgCl2

II. Metallic Bonding – Pooling

A. Metallic Bond: electrons move freely

between atoms

B. Many atoms share the same electrons

C. Explains why metals are malleable,

ductile, and conduct electricity.

D. One pool of atoms and electrons; not

individual molecules.

III. Covalent Bonds – Sharing

A. The Covalent Bond

1. Share electrons only within the same

molecule.

2. Molecule: neutral particle formed

when atoms share electrons

3. Be able to explain the differences in

ionic, metallic, and covalent

bonds!

B. Double and Triple Bonds

1. Atoms share more than 1 pair of

electrons

2. Examples: CO2 and N2

III. Polar and Non-Polar Molecules

A. Some atoms attract electrons better than

others

B. Unequal sharing causes one side of the

bond to be more – and the other

more +

C. Example: HCl

D. The Polar Water Molecule

1. Unequal sharing between H and O

2. Electrons more attracted to O

3. Molecules with out uneven charges

are non-polar

IV. Chemical Shorthand

A. Symbols for Atoms

1. One or two letter abbreviations

B. Symbols for Compounds

1. Use sub-scripts to indicate 2 or more