A Little Periodic Table History…

History of the Periodic Table

• Dmitri Mendeleev, a Russian scientist born in Siberia in 1834, is known as the father of the periodic table of the elements

• The periodic table is designed to help you predict chemical and physical properties of elements

Method Behind the Madness

• Mendeleev set out to find a pattern in the elements

• He wrote facts on paper cards for each element

Melting Point

Density

Colors

Atomic Masses

• After laying all of his cards out he noticed that by arranging them according to their properties they were arranged in order of increasing atomic mass

• Mendeleev was even able to use the patterns in his table to predict the properties of undiscovered elements

• The first periodic table was published in 1869

Method Behind the Madness (cont)

Mendeleev SongThe Genious of Mendeleev's Periodic Table - TedEd

Today, elements are arranged in order of increasing atomic number on the periodic table

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Element Location

Elements are located in three main categories on the periodic table based on their physical properties

Metals

Nonmetals

Metalloids

Physical Properties

Physical Property - a property of matter that can be observed or measured WITHOUT CHANGING the substance

Examples of Physical Properties

Color/Texture

Malleable – Can be pounded/rolled into a shape

Mass – How much matter is in an object

Ductile – Can be stretched into a long wire

Density – How tightly mass is packed into an object

Metals, Nonmetals, & Metalloids

Metals Most elements are metals. The 88

elements to the left of the stair-step line are metals or metal-like elements.

Physical Properties of Metals:

high luster (shininess)

good conductors of heat and electricity

high density (heavy for their size)

high melting point

ductile

malleable

Metals

Non-Metals Non-metals are found to the right of the

stair-step line. Their characteristics are opposite those of metals.

Physical Properties of Nonmetals:

no luster (dull appearance)

poor conductor of heat and electricity

brittle (breaks easily)

not ductile

not malleable

low density

low melting point

Non-Metals

Metalloids Elements on both sides of the zigzag line have

properties of both metals and nonmetals. These elements are called metalloids.

Physical Properties of Metalloids:

solids

can be shiny or dull

ductile

malleable

conduct heat and electricity, but not as well as metals

Antimony (Sb)

Metalloids

Scientists organize elements according to their physical and chemical properties

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How to Read the Periodic Table

• The Periodic table is designed to help you predict what an element's physical and chemical properties are

• You can also predict what elements will bond with each other

Elements are arranged:

Vertically into Groups (also called Families)

Horizontally Into Periods

Periodic Table Bitesize (only show part 1)

Periodic Table Arrangement

Groups or Families•Vertical columns on the periodic table

Periods•Horizontal rows of the periodic table

Why?

If you looked at one atom of every element in a group you would see…

Each atom has the same number of valence electrons (the electrons in its outermost shell).

Think back to the Bohr Model

An example…

The group 2 atoms all have 2 electrons in their outer shells

Be (Beryllium) Atom

Mg (Magnesium) Atom

Valence Electrons

• Effect the way an atom bonds, which determines many of the chemical properties of the elemento Atoms can have anywhere between 1

and 8 valence electrons

• This is why elements within a group usually have similar chemical properties

Chemical Properties

A chemical property is a characteristic that is observed when a substance changes into a different substance

Examples of Chemical Properties

Reactivity

Corrosion

Oxidation – rusting or tarnishing

Flammable – capable of

igniting

Combustible – capable of igniting at higher temps

Metal Reactivity

Metals – ReactivityReactivity decreases from left to right

Nonmetals – ReactivityReactivity increases from left to right

Not Reactive

If you looked at an atom from each element in a period

you would see…

Each atom has the same number of electron holding shells.

An example…

The period 4 atoms each have 4 electron containing shells

K (Potassium)

Atom Fe (Iron) Atom

Kr (Krypton)

Atom

4th Shell

Each group has distinct properties

The periodic Table is divided into several groups based on the properties of different atoms

For example…

The periodic table tells us several things…

Information on the periodic table:

•Atomic number

•Atomic symbol

•Mass number (Atomic Mass)

•Element name

•Group and period numbers

Periodic Table

Think Inside the BoxAtomic Number: Number of protons (also the number of electrons) in an atom of an

element.Element’s Symbol:

An abbreviation for the element.

Element’s Name

Atomic Mass:

Number of protons + neutrons.

OOxygen

16

8

Chemical Symbols• Shorthand way of representing the

elements

• Usually one or two letters

• Usually taken from the name of the element– Carbon-C, Calcium-Ca, Hydrogen-H,

Iodine-I, Oxygen-O, Chlorine-Cl

Chemical Symbols

• Some symbols come from their Latin name:– Gold-Au--aurum– Silver-Ag--argentum– Iron-Fe--Ferrum– Mercury-Hg--hydrogyrum

How do we know the number of subatomic particles in an atom?

• Atomic number: this number indicates the number of protons in an atom of a particular element– Ex: Hydrogen’s atomic number is 1

• So hydrogen has 1 proton

– Ex: Carbon’s atomic number is 6• So carbon has 6 protons

**The number of protons is a unique property that identifies an element.

Ex. 2 protons = He, 29 protons = Cu

Atomic Mass• Atomic Mass Unit (amu) is used to

measure the particles in atoms– Protons & Neutrons are about 1 amu– Electrons are MUCH smaller

• It takes about 2,000 electrons to equal 1 amu

• Atomic Mass = Protons + Neutrons

Atomic #

Symbol

Mass #

Pick an element off the Periodic Table and draw and label it just like this one!

Group and Period NumbersPeriod

NumbersGroup Numbers

Atomic No.Atomic No. = # of protons

Since protonsprotons & electronselectrons are EQUAL...the atomic no. also tells

you the # of # of electronselectrons

*Atomic # = # of Protons = # of electrons*

How Can I Find Out the Number of Protons and

Electrons?

Let’s take a look:

A = Atomic number

P = Number of protons

E = Number of electrons

These are all the same number!!

Atomic # = # of Protons = # of electronsAtomic # = # of Protons = # of electronsSo

NeutronsNeutrons = Mass Number – Atomic Number

Mass NumberMass Number = number of protons + number of neutrons

So

Then How Can I Find Out the Number of Neutrons?

Now let’s look at MAN:

M= Atomic Mass

- A= Atomic Number

N= # of Neutrons

Simple math!

Mass minus atomic number gives you the number of neutrons!!!

Let’s work a couple together

Let’s try Nitrogen!

Nitrogen

A= P= E= M= -A= N=

Boron

A= P= E= M= -A= N=

7

771477

555

1156

Now that we know how to figure out protons,

electrons, and neutrons…

Let’s try to create a Bohr Model

++

++++

Lithium

--

--

--

3

Li

Lithium7

Protons

Neutrons =

Electrons =

= 3

4 (7-3 = 4)

3 (2 in the 12 in the 1stst shell, 1 in the 2 shell, 1 in the 2ndnd shell shell)

Atomic Structure

Protons determine an element’s identity and valence electrons determine its chemical properties

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SUMMARY

1. The Atomic Number of an atom = number of

protons in the nucleus.

2. The Atomic Mass of an atom = number of

Protons + Neutrons in the nucleus.

3. The number of Protons = Number of Electrons.

4. Electrons orbit the nucleus in shells.

5. Each shell can only carry a set number of electrons.