Ions and Isotopes

ObjectiveStudents will be able to:• use atomic symbols to represent different

atoms and their isotopes.• Identify and define ions of different

elements

Some definitions

• Ion - an atom that has a positive or negative charge

How does something have a positive or negative charge?

Number of protons and electrons has to be different!

How can an atom become an ion?

• By gaining or losing electrons

Losing Electrons= CATION

Gaining Electrons= ANION

Cation

• Positive charge• Formed by the atom losing electrons

A neutral atom of sodium loses an electron and becomes Na+1

How many electrons does Li+1 have? Mg+2?

Anion

• Negative charge• Formed by the atom gaining

electronsChlorine gains one electron and becomes Cl-1

How many electrons does Br-2 have? F-1??

Why do atoms become ions?

• Atoms want to have a full outer shell (orbital)– one electron in outer shell will lose the

electron.– all but one electron will gain one.

Which is likely to become a cation?Which is likely to become an anion?

Summary of IonsLose electrons- become positive, which is a cationGain electrons- become negative, which is an anion

Electrons are gained or lost in the outermost shell• These are called valence electrons

Atomic NotationMass number= protons + neutron

Atomic number= Protons

Element Symbol

P=

N=

E=

20

20

20

P=

N=

E=

7

7

7

Atom Builder game

Isotopes

• Isotopes are atoms of the same element that have different numbers of neutrons.

• The mass number of an isotope tells you the number of protons plus the number of neutrons.

Difference?

Similarities?

H-1 H-2H-3

http://web.visionlearning.com/custom/chemistry/animations/CHE1.3-an-isotopes.shtml

Learning Check

Naturally occurring carbon consists of three isotopes, 12C, 13C, and 14C. State the number of protons, neutrons, and electrons in each of these carbon atoms.

12C 13C 14C 6 6 6

#p _______ _______ _______

#n _______ _______ _______

#e _______ _______ _______

Solution

12C 13C 14C 6 6 6

#p 6 6 6

#n 6 7 8

#e 6 6 6

Heavy WaterApplication of isotope

• Duterium- 21H can bind with oxygen

• Only occurs 1 in every 3200 molecules• Concentrated heavy water is used for

development of nuclear weapons

• Can be poisonous to plants and animals.

Cobalt-60Application of isotope

• Has one extra neutron in the nucleus– Radioactive and emits gamma radiation, which

can pass through materials easily– Sterilizes medical equipment and kills harmful

bacteria