classification of elements - trends in … · the periodic table has four blocks (s, p, d, f)....

Classification of Elements

What was another pattern of organization

you noticed on the periodic table?

Physical properties and states

3 main classifications of elements

Metals

Nonmetals

Metalloids

1. Metals

Elements that are shiny, smooth and clean

Solid at room temperature

Good conductors of heat and electricity

Malleable

Hammered flat

into a sheet

Ductile

Drawn out into

a wire

1. Metals

All group B and most group A elements

Staircase line is divider between metals

and nonmetals (Boron 3A and Astatine

7A)

ALMOST all elements on left side of table

are metals

What is the exception?

Hydrogen

Alkali and Alkaline Earth metals

(Group A) What does alkali mean?

basic

Alkali metals Group 1A (except hydrogen)

Alkaline earth metals Group 2A

Both alkali and alkaline earth metals are chemically reactive Alkali metals more reactive…why do you think?

Valence electrons…how many do group 1A elements have?

Is this stable?

Transition Elements

(Group B)

2 categories

Transition metals

Inner Transition Metals (2 types)

Inner Transition Metals

Located along the bottom of the periodic table

2 sets

Lanthanide series

Top row of the inner transition elements

These elements are used as phosphors

Substances that emit light when struck by electrons

Where have we seen this before?

Where do we see this today?

Actinide series

Bottom row of the inner transition elements

Transition elements

All other group B elements that are not

inner transition elements

Basically the Group B elements we see on

the actual periodic table…

Think of it as the ‗continental US‘

3 main classifications

of elements

• Metals

• Nonmetals

• Metalloids

2. Nonmetals

Occupy the upper right side of the periodic

table

Usually gases

Brittle, dull-looking solids

Poor conductors of heat and electricity

Bromine (Br) is the only nonmetal that is

liquid at room temperature

Important nonmetals

Group 7A

Halogens Highly reactive elements

What does this mean?

Why are they highly reactive?

Look at the valence electrons

Group 8A

Noble gases Highly unreactive

Why?

8 valence electrons

3 main classifications

of elements

• Metals

• Nonmetals

• Metalloids

3. Metalloids

Border the stair-case line

Elements with physical and chemical

properties of both metals and non-metals

Silicon and germanium

Two of the most important metalloids

Anyone know why?

Used in computer chips and solar cells

Everyday Examples

Metals? Jewelry

Pot and pans

Cars

Nonmetals? Air we breath

Nitrogen

Neon signs

Diamonds

Metalloids? Computer chips

Everyday Examples

Metals? Jewelry

Pot and pans

Cars

Nonmetals? Air we breath

Nitrogen

Neon signs

diamonds

Metalloids? Computer chips

Organizing the Elements by

Electron Configuration

Electron configuration determines the

chemical properties of an element.

Recall electrons in the highest principal

energy level are called valence

electrons.



All group 1 elements have one valence

electron.

All group 2 elements have two valence

electrons.



The energy level of an element‘s valence electrons indicates the period on the periodic table in which it is found.

The number of valence electrons for elements in groups 13-18 is ten less than their group number.

After the s-orbital is filled, valence electrons occupy the p-orbital.

Groups 13-18 contain elements with completely or partially filled p orbitals.



The d-block contains the transition metals and is

the largest block.

There are exceptions, but d-block elements usually

have filled outermost s orbital, and filled or partially

filled d orbital.

The five d orbitals can hold 10 electrons, so the d-

block spans ten groups on the periodic table.



The f-block contains the inner transition metals.

f-block elements have filled or partially filled

outermost s orbitals and filled or partially filled 4f and

5f orbitals.

The 7 f orbitals hold 14 electrons, and the inner

transition metals span 14 groups.

Periodic Trends

Objectives:

Compare period and group trends of

several properties.

Relate period and group trends in atomic

radii to electron configuration

Periodic Trends

Atomic Radius

Atomic radius – is determined by the amount of

positive charge in the nucleus and the number of

valence electrons of an atom. It is usually

measured in picometers (10-12).

For metals, atomic radius is half the distance

between adjacent nuclei in a crystal of the

element.

For nonmetals, the atomic radius is the distance

between nuclei of identical atoms.

Atomic Radius

Atomic Radius

The periodic trend: decreases from left to right

(periods) and increases top to bottom

(groups) due to the increasing positive charge

in the nucleus.

Atomic Radius

Atomic Radius

Atomic radius generally increases as you move

down a group.

The outermost orbital size increases down a

group, making the atom larger.

Valence electrons are not shielded from the

increasing nuclear charge because no additional

electrons come between the nucleus and the

valence electrons.

Ionic Radius

Ions – atom(s) that gain or lose one or more electrons

to form a net charge.

Ionic radius is the radius of a charged atom.

When atoms lose electrons and form positively

charged ions, they always become smaller.

Lost electrons are usually valence electrons and

could leave the outer orbital empty and therefore

smaller.

Electrostatic repulsion between remaining

electrons decreases and pulls closer to nucleus.

Ionic Radius

When atoms gain electrons and forms a

negatively charged ion, they become larger.

Increased electrostatic repulsion increases

distance of outer electrons.

Ionic Radius

Periodic Trend:

Radius of an ion decreases from left to right

(periods) until charge changes and then the

radii increases dramatically.

After the change, the radius continues to

decrease.

Ionic radii increases top to bottom (groups)

until change in charge.

Ionic Radius

Ionization Energy

Ionization energy is the energy needed to remove an electron from the positive charge of the nucleus of a gaseous atom – how strongly a nucleus holds on to an electron.

First ionization energy is the energy required to remove the first electron.

Removing the second electron requires more energy, and is called the second ionization energy.

Ionization Energy

Atoms with large ionization energies have a strong hold of its electrons and are less likely to form positive ions.

Atoms with low ionization energies lose their outer electrons easily and readily form positive ions.

The ionization at which the large increase in energy occurs is related to the number of valence electrons.

Ionization Energy

Periodic Trend:

First ionization energy increases from left to right

across a period.

First ionization energy decreases down a group

because atomic size increases and less energy is

required to remove an

electron farther from

the nucleus.

Ionization Energy

The octet rule states

that atoms tend to

gain, lose or share

electrons in order to

acquire a full set of

eight valence

electrons.

The octet rule is

useful for predicting

what types of ions an

element is likely to

form.

Trends in Ionization Energy

Low Energy = Easier to remove electron

High Energy = Difficult to remove electron

Ionization Energy

Shielding Effect

Electronegativity

Electronegativity of an element indicates

its relative ability to attract electrons in a

chemical bond.

Measured in Paulings: numbers 4 and less.

Electronegativity

Ability to attract

An electron

Forms a Anion

X -> X-

Electronegativity

Periodic Trend: electronegativity decreases down a

group and increases left to right across a period.

Boiling Point

Boiling Point Trends

-Georges Lemaitre came up with the Big Bang Theory in 1921 The Big Bang Theory:

• Matter from all the universe came from a very hot central point.

• Sooner or later, the central point began to cool…

• 15 billion years ago those atoms were drawn together by gravity.

• This region exploded and matter was thrown outward

The Big Bang Theory

In 1929, Edwin Hubble discovered that the universe is expanding.

The universe is filled with radiation that is left-over from the Big Bang called Cosmic Microwave Background Radiation, which was discovered in the 1960‘s

Red shift- tells us that objects are moving away from us.

Evidence for Big Bang Theory

Many Christians believe that God created the

Earth, and all the universe. Many criticize the Big

Bang Theory and come up with many

explanations on why it‘s not correct.

There are also two other scientific theories

explaining how the universe could have been

created.

If the universe really was created by an explosion,

and was spread evenly, then there shouldn‘t be

clusters of galaxies, stars, planets, etc.

Big Bang Theory Weaknesses

Random Facts About the

Big Bang Theory

If we were to look at the universe one

second after the Big Bang, what we would

see is a 10 billion degree sea of neutrons,

protons, electrons, (and such things as

anti-electrons, photons, and nutrions).

Some scientists believe that the universe

may contract back to a central point.

Scientists like to call this the ―Big Crunch‖.

Natural Elements

Hydrogen and Helium were the first to form after

the explosion

E = mc2 When helium formed by the fusion

of hydrogen atoms, some mass was lost as

energy.

Fusion reactions release an enormous quantity of

energy—enough to maintain the heat at the center

of a star

The continued fusion of atoms formed the other 93

natural elements.

Nuclear Fusion

4 1H -----------> 4He

occurs in the core of stars

Fusion in SuperGiant Stars

Betelgeuse is a red giant star in Orion

that is currently fusing Helium

and will become a supernova

Size comparisons video

3 4He ---------> 12C

http://www.youtube.com/watch?v=Dv6OtEnIAQk&feature=related

Elemental Abundance

1. Hydrogen

2. Helium

3. Oxygen

4. Carbon

Rare earth elements

Alchemy

Synthetic Elements

Transmutation:

The changing of

one element into

another

Alchemists tried to

change such things

as lead into gold.

Modern chemists

have produced

elements with larger

nuclei using

equipment called

particle accelerators

Lawrence‘s Cyclotron The first particle accelerator

Superheavy Elements

Transuranium Elements

Produced by nuclear collisions

Key Concepts

The elements were first organized by increasing

atomic mass, which led to inconsistencies. Later,

they were organized by increasing atomic

number.

The periodic law states that when the elements

are arranged by increasing atomic number, there

is a periodic repetition of their chemical and

physical properties.

The periodic table organizes the elements into

periods (rows) and groups (columns); elements

with similar properties are in the same group.

Key Concepts

Elements are classified as either metals, nonmetals, or metalloids.

The periodic table has four blocks (s, p, d, f).

Elements within a group have similar chemical properties.

The group number for elements in groups 1 and 2 equals the element‘s number of valence electrons.

The energy level of an atom‘s valence electrons equals its period number.

Key Concepts Atomic and ionic radii decrease from left to right across

a period, and increase as you move down a group.

Ionization energies generally increase from left to right

across a period, and decrease as you move down a

group.

The octet rule states that atoms gain, lose, or share

electrons to acquire a full set of eight valence

electrons.

Electronegativity generally increases from left to right

across a period, and decreases as you move down a

group.

classification of elements - trends in … · the periodic table has four blocks (s, p, d, f)....

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