Daniel R. BarnesInit:10/2/09

. . . look at a drawing of an atom and determine its element, its atomic number, its mass number, and its electric charge.

“SWBAT = “Students will be able to”

This lesson is the reverse of the atom drawing lesson.

In the atom drawing lesson, I gave you a chemical symbol, a mass number (sometimes), and an electric charge (sometimes), and from that you were supposed to draw an atom.

In this lesson, I will show you a drawing of an atom, and you will need to determine its element, its atomic number, its mass number, and its electric charge.

= -1

= 0

Before we get started with identifying full atoms, we’d better make sure you know all the parts, first.

= “proton”

= “neutron”

= “electron”

electric charge

= +1

electric charge

electric charge

The clump in the center of the atom is called the “nucleus”.

The big circles surrounding the nucleus like the layers of an onion are called “shells”.

WARNING: What one person means by “shell” or “energy level” may be different than what other people mean.

ATOM IDENTIFICATIONOkay. Let’s do what we came here to do.

ATOM IDENTIFICATIONFirst, identify what element the atom is by counting the number of protons in the nucleus.

This atom has five protons, so its atomic number is five.

Now that we know its atomic number, we can look on the periodic table to figure out what element it is.

Element number five is . . . boron.

ATOM IDENTIFICATIONThis is a boron atom, so we can write the symbol for boron . . .

B

Next, we’re going to write the atomic number of the atom in the lower left subscript area.

You don’t really need to do this most of the time, because all boron atoms automatically have an atomic number of five, but we’re going to do it just for kicks.

5

ATOM IDENTIFICATION

In other words . . .

Next, we need to figure out the mass number, which is the total number of things in the nucleus.

Mass # = # of protons + # of neutrons

Mass # = 5 + 6 = 11

11B5

ATOM IDENTIFICATION

After all, neutrons are neutral.

Finally, we need to calculate the electric charge of the atom. The protons and electrons matter for this, but not the neutrons.

Electric charge = # of protons - # of electrons

Electric charge = 5 – 4 = 1 = +1 “+”

+11B5

Let’s do a few more to see if you’ve got it.

10 Atomic number is 10 Element is neon

Ne

7 Mass number = 10 + 7 = 17

17

6 Electric charge = 10 – 6 = 4 = “4+”

4+

10 Atomic number is 10 Element is neon

Ne

4 Mass number = 10 + 4 = 14

14

2 Electric charge = 10 – 2 = 8 = “8+”

8+

8 Atomic number is 8 Element is oxygen

O

2 Mass number = 8 + 2 = 10

10

4 Electric charge = 8 - 4 = 4 = “4+”

4+

9 Atomic number is 9 Element is fluorine

F

3 Mass number = 9 + 3 = 12

12

10 Electric charge = 9 - 10 = -1 = “-”

-

7 Atomic number is 7 Element is nitrogen

N

3 Mass number = 7 + 3 = 10

10

10 Electric charge = 7 - 10 = -3 = “3-”

3-

2 Atomic number is 2 Element is helium

He

9 Mass number = 2 + 9 = 11

11

10 Electric charge = 2 - 10 = -8 = “8-”

8-

4 Atomic number is 4 Element is beryllium

Be

7 Mass number = 4 + 7 = 11

11

8 Electric charge = 4 – 8 = -4 = “4-”

4-

6 Atomic number is 6 Element is carbon

C

6 Mass number = 6 + 6 = 12

12

0 Electric charge = 6 – 0 = 6 = “6+”

6+

1 Atomic number is 1 Element is hydrogen

H

0 Mass number = 1 + 0 = 1

1

5 Electric charge = 1 – 5 = -4 = “4-”

4-

5 Atomic number is 5 Element is boron

B

3 Mass number = 5 + 3 = 8

8

0 Electric charge = 5 – 0 = +5 = “5+”

5+

8 Atomic number is 8 Element is oxygen

O

6 Mass number = 8 + 6 = 14

14

8 Electric charge = 8 - 8 = 0 = “”

3 Atomic number is 3 Element is lithium

Li

1 Mass number = 3 + 1 = 4

4

10 Electric charge = 3 - 10 = -7 = “7-”

7-

More practice atoms to come later . . .