The Periodic Table So you thought you knew ...

Mendeleev’s Arrangement

By mid-1800’s, chemists needed a way to organize the 50+ elements already discovered

Russian chemist, Dimitri Mendeleev found a pattern when he placed the elements in order of increasing atomic mass

The properties of the elements appeared in regular intervals, or periodically - hence, the Periodic Table

The Modern Periodic Table Most elements with atomic numbers less than

93 are natural - the exist naturally on Earth

The other elements are synthetic(man-made)

Once the relationships between elements were established, scientists could predict other elements that could be made Based on what the atomic structure should be

(according to position on periodic table)

Classes of Elements

We can predict the physical and chemical properties of an element based on its position in the table

3 classes: Metal Non-metal Metalloid

Copy the following table into your notes:

Classes of Elements cont’d

MATERIAL

STATE AT ROOM TEMP.

APPEARANCE

CONDUCTIVITY(Heat & Electricity)

MALLEABILITY & DUCTILITY

Metals

Non-Metals

Metalloids

Classes of Elements cont’d

MATERIAL

STATE AT ROOM TEMP.

APPEARANCE

CONDUCTIVITY

MALLEABILITY & DUCTILITY

Metals Solid (except mercury – liquid)

Shiny Good Malleable Ductile

Non-Metals

Some gas, some solid (except Bromine – liquid)

Not very shiny

Poor Brittle Not ductile

Metalloids

Solids Can be shiny or dull

May conduct electricity,Poor conductor of heat

Brittle Not ductile

Where are they on the PT?

Metals

Non-Metals

Metalloids

In-Class Assignment: Read pages 202 – 204: Mining For Metals; Metals

and Health; Diamond Mining. Answer the following questions:

1. What compound is used to extract gold from ore?2. What are the negative effects of gold mining and

refining?3. How is iron used in your body?4. What organs can be injured if iron levels in the body

are too high?5. Name the two processes that result in high

concentrations of metals in animals.6. Why are waterways a key source of mercury

poisoning? 7. Answer question 1 on p. 203.8. In point form, describe four ways diamond mine

companies contribute to their local communities. Do you think mine companies did this around 100 years ago?

What Else Can the Periodic Table Tell Us?

Elements are organized into periods and groups

Periods are horizontal rows, numbered 1 to 7, starting from the top

Rows and rows... Even though they skip some squares in between,

all of the rows go from left to right

Elements in the same row have something in common - the same number of energy levels (or electron shells)

Every element in the top row (the first period) has one electron shell for its electrons

All of the elements in the second row (the second period) have two electron shells for their electrons, etc

At this time, the maximum number of energy levels or electron shells for any element is seven

Groups

Groups (or families) are vertical columns

They are numbered 1-18, starting on the left

Groups When a column goes from top to bottom, it's

called a group. The elements in a group have the same

number of electrons in their outer energy shell

Every element in the first column (group one) has one electron in its outer shell.

Every element on the second column (group two) has two electrons in the outer shell... etc

N.B. There are exceptions to the order when you look at the transition elements, but you get the idea.

For now, “1,2, skip a few, minus 10”

Happy Atoms Electrons want to be happy

They are happiest when their outermost energy level is full of electrons!

During a chemical reaction, one atom can join with another atom by gaining, losing, or sharing valence electrons

Valence electrons determine how reactive an element is

All in the Family (Anybody? Anybody?)

Families are groups of elements with similar chemical properties

Each family reacts and behaves differently

4 important families are1. Alkali Metals2. Alkaline Earth Metals3. Halogen Gases4. Noble Gases

Alkali Metals (Group 1)

Traits: Very reactive – why? They all have 1 electron

in their outer shell. That’s 1 away from being happy (full shell)

Increased desire to bond (and lose electron) = more reactive

Alkali Metals cont’d

MORE TRAITS:

Low melting points

Shiny

Light in weight

Soft

EG. SODIUM

Alkaline Earth Metals – Group 2

2nd most reactive family Needs to get rid of 2

valence electrons to be happy

When heated, they will burn in air and produce bright, colourful flames Eg. Magnesium Often used in fireworks

Very important in physiology Eg. calcium

Eg. Magnesium

Halogens – Group 17

How many valence electrons ? 7 – only 1 short of being full

Because they are so close to being happy, they combine with many different elements Very reactive non-metals! Often bond with elements from Group 1

Halides Extremely corrosive

Chlorine and Iodine are both used as disinfectants

When a halogen combines with another element, the compound is called a halide Sodium Chloride (NaCl) is a

halide

Inert Gases - Group 18

Aka Noble gasesAka group zeroHappiest elements of all!

Outer electron shells are fullHappy not reacting with other

elements – rarely combine Non-reactivity = inert

Odourless, colourless gases (at room temp.)

When they do bond, they were forced

Outlaws:

HYDROGEN

Has talents of 2 groups: one and seven

either missing an electron or have one extra

NOT an alkali metal It’s a gas

HELIUM

Even though it only has 2 valence electrons, it is still in the inert gas family

There’s one in every family, right?

Transition Metal Groups

Transition metals (groups 3-12) are special They have a lot of electrons that are

distributed in different ways (i.e. They don’t follow the pattern)

Can use the two outermost shells to bond with other elements (instead of just outermost) Most have two shells that aren’t “happy”

The last two...LANTHANIDE SERIES Aka: Rare-earth

metals or inner transition metals

Found naturally on earth Except for Promethium

(Pm) - radioactive

ACTINIDE SERIES All radioactive

elements Some with higher

atomic numbers have only been made in labs Particle accelerators