ANTHONY GATES
CHEMISTRY
UNIT 4

Brief History

Mid-1800’s: only 70 elements were found , but scientist knew many more existed.

Scientists tried to organize the elements by chemical properties, but failed.

Dimitri Mendeleev

Organized the elements by increasing mass.

Used notecards

Left blank spaces where he knew there was an element, but they weren’t discovered yet.

The result was the first periodic table of elements.

Mendeleev cont.

After organizing the table, Mendeleev noticed repeating similarities in chemical and physical properties.

The Editing Process

When organizing his table,
Mendeleev noticed that Iodine had a smaller mass than Tellurium, but it had more properties in common with bromine and chlorine than tellurium.

Mendeleev switched the places of these elements to match up the properties.

This occurred with a few more elements.

Henry Mosely…Rethinking the Table

Discovered that each element has a different number of protons and determined the atomic number for each element.

Arranged the chart according to the atomic number (number of protons) resulting in the
Modern Periodic Table.

Periodic Law

Periodic Law: when elements are arranged in order of increasing atomic number, there is a periodic repetition of their physical and chemical properties.

Parts of the Periodic Table
Periods:

Horizontal rows

Side-to-side

7 total
Groups:

Vertical columns

Up and down

Also called families
(share characteristics)

Classes of Elements

There are three classes of elements:

Metals

Nonmetals

Metalloids

Metals

Majority of the elements

Good conductors of electricity and heat

Shiny/high luster (reflect light)

Ductile

Can be drawn into a wire

Malleable

Can be hammered into thin sheets without breaking

Nonmetals

Tend to be gasses at room temperature

Poor conductors of heat or electricity

Brittle

Shatter if hit by a hammer

Metalloids

Stair-step of elements

Individual metalloids tend to share properties of both metals and nonmetals

Mission Possible…
“Elemental Research”


Your homework is to do a little research:

Pick an element out of the beaker and write down the name of that element on the worksheet. From there you will have to find out information about the element including things like:

Chemical Symbol

Location on the periodic table (group and period number)

Properties (similar to the ones in the last three slides)

Element Class

How is it commonly used in the world?
If you missed this class, I will expect that you will pick any element on the table and fill out the Elemental Research worksheet found on my website.

Bellwork

Come up with two properties of metals and two properties of nonmetals with a partner seated near you.
(be prepared to share with the class)

Pull out your homework and be prepared to present your finding to the class.

Active Metal Group

Alkali Metals

Very reactive - react violently w/ H
2
O

Not found freely in nature

Soft metals, silver in color

Alkaline Earth Metals

Reactive Metals < Group 1

Harder, stronger than Group 1

Transition Metal Group

Transition Metals:

Outermost s and d orbitals contain electrons

Harder and denser than Active Metal Group
(Group 1 & 2)

Less reactive

Found in nature

Inner-Transition Metals

Inner Transition Metals:

Outermost s and f orbitals contain electrons

Lanthanide Series

“Rare” earth metals

Shiny, Reactive

Actinide Series

All unstable and radioactive

Halogen Group

Halogens

Very reactive nonmetals

7e- in outer energy level/shell

Reacts easily to gain 1e- = full shell

Noble Gas Group

Noble Gases:
 outer s and p orbitals are full

_s 2 _p 6

8e- in outer shell: stable!

Also called the inert gases

They don’t react because they are “happy”

They don’t want to lose or gain electrons

Representative Elements

Representative
Elements:

Elements whose s and p orbitals are partially filled

“the 2 towers”

Periodic review

Which group(s) contain the alkaline earth metals?

Group 2

Which group(s) contain the noble gases?

Group 18

Which group(s) contain the transition metals?

Groups 3-12

Bellwork

With a partner near you, identify where on the periodic table, the following groups of elements are located:

Halogens

Alkaline Earth Metals

Inner Transition Metals

Noble Gases

Alkali Metals

Transition Metals

Learning objective

I can describe relative properties of elements based on periodic trends.

Periodic Trends

Mendeleev noticed that after creating the periodic table that there was a periodic set of similarities amongst the physical and chemical properties of the elements.

Trend: Atomic Size (radius)

One half the distance between the nuclei of two atoms of the same element joined together.

Trend: Atomic Radius

Atomic radius increases as you move down the periodic table.

Higher energy levels make the atom larger.

Trend: Atomic Radius

Atomic radius decreases as you move to the right on the periodic table.

As you add another proton to the nucleus, the charge pulls the electrons closer to the nucleus, causing a decrease in size.

Practice

Which of the following pairs has the greater atomic size?

K or Cr

Ga or B

S or Sn

Trend: Ionization Energy

The energy required to remove an electron from an atom.

1 st ionization energy: energy required to remove the
1 st electron from an atom

2 nd ionization energy: energy required to remove the 2 nd electron from an atom.

3 rd , 4 th , 5 th …

Trend: Ionization Energy

Ionization energy decreases as you go down

The attractive force between the nucleus and the electrons is weaker with larger distance.

Less energy is required to overcome this force.

Trend: Ionization Energy

Ionization energy increases as you move to the right on the periodic table.

Increased attractive force between nucleus and electrons with more protons.

More energy is required to overcome this force.

Practice

Which of the following has the greater ionization energy?

Cl or Al

Na or Rb

O or Si

Trend: Electronegativity

The ability of an atom to attract electrons when the atom is in a compound.

Trend: Electronegativity

Noble Gases are not electronegative because they don’t want to react with other atoms.

Based on a scale from 0.0 - 4.0 called the
Pauling Scale

Fluorine has the highest electronegativity at 4.0

Trend: Electronegativity

Electronegativity decreases as you move down a group.

Bonding electrons are farther away; thus the nucleus can’t pull as hard on them.

Trend: Electronegativity

Electronegativity increases as you move to the right.

Metals (left): want to lose electrons

LOW electronegativity

Nonmetals (right): want to gain electrons

HIGH electronegativity

Practice

Which of these has the greater electronegativity?

Br or Cu

C or Pb

Ne or N

S or F

Bellwork

Compare silver and mercury. Which one will have the greater…

Atomic Radius

Ionization Energy

Electronegativity

Discuss with someone near you, why do other elements want to be like the Noble Gases?

Pull out your homework.

Learning Objective

I can identify how atoms can become ions and show the correct symbol for a given ion.

Atoms vs. Ions

Atoms lose or gain electrons to obtain the electron configuration of a noble gas.

This causes the atom to take on a charge.

Atoms = NEUTRAL

Ions = CHARGED ATOMS

Ion Types

Positive Ions (Cations): formed by an atom losing electrons p + e charge

Na: 1s 2 2s 2 2p 6 3s 1 11 11 none

Na + : 1s 2 2s 2 2p 6

Ne: 1s 2 2s 2 2p 6
11 10 +1
10 10 none

Ion Types

Negative Ions (Anions): formed by an atom gaining electrons p + e charge

O: 1s 2 2s 2 2p 4 8 8 none

O -2 : 1s 2 2s 2 2p 6 8 10 -2

Ne: 1s 2 2s 2 2p 6 10 10 none