ISOTOPES

WHAT IS AN ISOTOPE?

Atoms of the same element with different numbers of neutrons. What has changed if there is a different

number of neutrons. HINT: look at your periodic tables. Something must have changed.

WHAT IS AN ISOTOPE

If you have a different number of neutrons, that means your atomic mass has changed. Remember that atomic mass = neutrons +

protons

THE NUMBER OF PROTONS NEVER CHANGES. Why doesn’t this number ever change?

WHAT IS AN ISOTOPE?

If you change the number of protons you now have a different element. EX: If you have an atom of Ne (Neon) with

11 protons now.. You actually would have an atom of Na (Sodium)

CALCULATE THE FOLLOWING IN SODIUM

Protons Neutrons Electrons

CALCULATE THE FOLLOWING IN SODIUM

Protons 11 Neutrons 12 Electrons 11

Draw out the model

TWO SODIUM ATOMS

Sodium with 11 protons and 12 neutrons.

** This is what we see on the periodic table.

Sodium with 11 protons and 13 neutrons.

** Different from periodic table

HOW DO WE SHOW ISOTOPES?

X: element symbol

A: Mass Number# protons + # neutrons in the nucleus

Always larger than Z

Z: Atomic number

#protons

A, X, and Z are very important

to remember

!

TRY IT IN YOUR NOTES

What is the element?

How many protons are in the element?

What is the elements atomic mass?

Na

23

11

TRY IT IN YOUR NOTES

What is the element? Sodium

How many protons are in the element? 11

What is the elements atomic mass? 23

Na

23

11

TRY IT IN YOUR NOTES

What is the element?

How many protons are in the element?

What is the elements atomic mass?

Cl33

17

TRY IT IN YOUR NOTES

What is the element? Chlorine

How many protons are in the element? 17

What is the elements atomic mass? 33

Cl33

17

TRY IT IN YOUR NOTES

An atom of Nitrogen

7 protons

Mass number of 14

TRY IT IN YOUR NOTES

An atom of Nitrogen

7 protons

Atomic mass of 14

N14

7

HOW ELSE DO WE SHOW ISOTOPES?

Sodium-23

Mass Numbe

r

Element

Name

** This is what we see on the periodic table

Questions, Comments, Concerns?

Please take out your whiteboards.

Write the isotope symbol for the chemical element that has 6 protons and 8 neutrons (write the symbol both ways)

Write the isotope symbol for the chemical element that has 6 protons and 8 neutrons (write the symbol both ways)

Carbon – 14 C14

6

Write the isotope symbol for the chemical element that has 17 protons and 16 neutrons

Write the isotope symbol for the chemical element that has 17 protons and 16 neutrons

Cl or Chlorine-3317

33

How many protons are in the isotope 54Cr? (Chromium-54)

How many protons are in the isotope 54Cr? (Chromium-54)

24 just like all Chromium Protons NEVER CHANGE

TRUE/FALSE

Isotopes of an element always have the same number of neutrons. A. False B. True

TRUE/FALSE

Isotopes of an element always have the same number of neutrons. A. False

TRUE/FALSE

Isotopes of an element always have the same number of protons. A. False B. True

TRUE/FALSE

Isotopes of an element always have the same number of protons. B. True

Z = 9 A = 29

Draw the symbol. How many protons? How many neutrons?