Ch. 2 - Atomic Structure

I. Subatomic Particles

II. The Periodic Table

Subatomic Particles

POSIT IVECHARG E

PROT ONS

NEUT RALCHARG E

NEUT RONS

NUCLEUS

NEG AT IVE CHARG E

ELECT RONS

AT OM

Most of the atom’s mass.

NUCLEUS ELECTRONS

PROTONS NEUTRONS NEGATIVE CHARGE

POSITIVE CHARGE

NEUTRAL CHARGE

ATOM

QUARKSAtomic Numberequals the # of...

equal in a neutral atom

Subatomic Particles (Parts of the Atom)

Particle Symbol Charge Relative Mass

Electron e- - 0 amu

Proton p+ + 1 amu

Neutron n0 0 1 amu

Location of Subatomic Particles

Electron (-)

Nucleus

Proton (+)

Neutron

Atoms Family Album

Click on the Light Bulb to See the Atoms Family Album

Atoms are building blocks of

elements.

Each element is made of only

one type of atom.

Example: Aluminum is made

only of aluminum atoms.

Each element’s atoms are

different from atoms of other

elements.

Example: Aluminum’s atoms are

different from copper’s atoms.

Atomic Number

The number of protons in the atom. (If the atom is neutral, it is also the number

of electrons.)

Atomic Number on the Periodic Table

6

CSymbol

Atomic Number

All atoms of an element have the same number of protons!

6

CCarbon

6 protons

Learning Check State the number of protons (or electrons) for atoms of each of the following:

1. Nitrogen A) 5 B) 7 C) 14

2. Sulfur A) 32 B) 16 C) 6

3. BariumA) 137 B) 81 C) 56

Mass NumberCounts the number

of protons plus neutronsprotons plus neutrons

in an atom, so to find the number of neutrons you

simply use this formula:

Mass # - Atomic # = # of neutrons

Atomic SymbolsShow the mass number and atomic number

Give the symbol of the element

6

C12Mass Number

Atomic Number

Number of ElectronsAn atom is neutral The net charge is zeroNumber of protons = Number of electrons

Atomic number = Number of electrons

Subatomic Particles in Some Atoms

8 15 30

O P Zn 16 31 65

8 p+ 15 p+ 30 p+

8 e- 15 e- 30 e-

8 n 16 n 35 n

Drawing Atomic Models

The first electron shell/level/cloud can hold 2 electrons

The second electron shell/level/cloud can hold 8 electrons

The third electron shell/level/cloud can hold 18 electrons

The neutrons and protons are in the nucleus (center)

Let’s draw a model for sodium (Na) How many protons

does it have?

• 6 (same as atomic number)

How many neutrons?

• 6 (atomic mass - atomic number = 12 - 6 = 6)

How many electrons?

• 6 (same as # of protons)

C6

12

Where do we put this stuff?

6 protons, 6 neutrons, 6 electrons

Protons and neutrons go in the nucleus

Electrons go in the orbitals/shells/clouds

e-

e-

e-

e-

e-

e-

6 p+

6 n0

Protons and neutrons go in the nucleus

How many electrons fit in the first shell?How many electrons fit in the second shell?How many electrons fit in the third shell?

Examples of 3-d Bohr Models

Visionlearning

The Elements Song

Lewis Dot Structure

C• •••

What does this symbol mean?

CarbonDots tell you valence electrons

••C• •

Valence Electrons?

C• •••

Valence electrons are electrons in the outermost shell of an atom. They are involved in forming bonds with other elements.

How do you figure out valence electrons?

C12

6Protons?

6 (same as atomic number)

Neutrons?

6 (atomic mass - atomic number)

Electrons?

6 (same as atomic number)

So we know carbon has 6 electrons…now what?

6p+

6n

e-

e-

e-e-

e-

e-

How many are in the outermost shell?

The first shell holds 2.Now 4 are left.

They go in the second shell.

4!

4 valence electrons=4 dots!

C• •••

How to draw your dots…

•Cl• ••• ••

3

2

1

4

7

6

5

Chlorine has 7 valence electrons. First put dots on each side before you double up.

An Easy Trick!

(1)5(1)4 (1)8(1)7(1)62 (1)31

Exception!

To figure out how many dots to draw

If an element has a full outermost shell, that means it does not react with anything.

Ne• ••••

• ••

Which elements have full outermost shells?

Now you try…1.Lithium

2.Nitrogen

3.Calcium

4.Oxygen

5.Fluorine

•

•

•

••N

•Li

•

• Ca•

•••

••O

••

•

••••F