Building Atoms. The Periodic Table Will Help You! The PTE is an arrangement of the elements into groups that have similar properties. The horizontal rows.

Building Atoms

The Periodic Table Will Help You!The PTE is an arrangement of the elements into groups that have similar properties.

The

horiz

onta

l row

s ar

e pe

riods

. The columns are groups or families.

A closer look

Each square looks like this:

O8

15.999Oxygen

Atomic Number = Protons OR Electrons

Average atomic mass

Symbol

Drawing the nucleus

Draw the nucleus of an oxygen-16 atom:

O8

15.999Oxygen

++

+++

+

+

+

We often replace the picture with: 8p/8n

Protons = 8Neutrons = 16 - 8 = 8

What about the electrons?

The electrons will go on orbits (energy levels): 8p/8n

O8

15.999Oxygen

Atomic Number = Protons OR Electrons

Find the element in the PTE

1 orbit2 orbits3 orbits4 orbits

5 orbits6 orbits

Draw the correct number of orbits.

O

let’s put the electrons in

8p/8n

Rules!

The first orbit holds up to 2 electrons.The second orbit holds up to 8 electrons.

The order you put them in matters.

In general

1 2

3

4

5

6

7

8

9

10

11

12

13

14

15

16

17

18

Rules!

The 1st orbit holds up to 2 electrons.The 2nd orbit holds up to 8 electrons.The 3rd orbit holds up to 8 electronsThe 4th & 5th each hold up to 18 electrons

Lets try Carbon!

Draw a carbon-12 atomHow many orbits?

C6

12.011Carbon

2

6p/6n

Phosphorus

Draw a phosphorus-31 atomHow many orbits?

15p/16n

3

Valence Electrons

Valence electrons are electrons in the outermost orbit of an atom.

This carbon atom has 4 valence electrons.

The inside orbit is filled.

6p/6n

Another wayYou can also figure out how many valence electrons are in an atom by looking at your periodic table:

IGNORE THESE GUYS!

1 Va

lenc

e el

ectr

on

2 Va

lenc

e el

ectr

ons

3 Va

lenc

e el

ectr

ons

4 Va

lenc

e el

ectr

ons

5 Va

lenc

e el

ectr

ons

6 Va

lenc

e el

ectr

ons

7 Va

lenc

e el

ectr

ons

8 Va

lenc

e el

ectr

ons

2

Helium is a special exception-it has only 2!