Atomic Structure & The Periodic Table

Chapter 5

Objectives

Students will be able to: Recognize where atoms of some common elements are

found and how they are named. Describe atomic structure and how that structure

determines an elements identity. Identify number of proton, electrons, and neutrons using a

periodic table. Interpret information about an element using a periodic

table. Evaluate and calculate the number of atomic particles and

the atomic mass using a chocolate chip cookie.

All matter is made of atoms!

Everything in this room is made up of atoms!

2400 Years Ago….

Greek philosophers proposed that everything on Earth was made of only four basic substances– air, water, fire, and earth.

Everything else contained a mixture of these substances.

Today chemists know that about 100 basic substances, or elements, account for everything we see and touch.

Types of Atoms in Earth’s Crust and Living Things Hydrogen atoms account for about 90% of

the total mass of the universe, but make up only 1% of the Earth’s crust. Most of these atoms are combined with oxygen atoms in the form of water.

Living things contain at least 25 types of atoms. Primarily oxygen, carbon, hydrogen, and nitrogen.

Names and Symbols of Elements

Elements get their names in many different ways. Magnesium was named for the region in Greece

known as Magnesia. Lithium comes from the Greek word lithos, which

means “stone” Neptunium was named after the planet Neptune.

Li

Mg Np

Element Symbols Each element has its own unique symbol. For

some elements, the symbol is simply the first letter of its name.

Hydrogen- H Sulfur- S Carbon- C

The symbols for other elements use the first letter plus one other letter of the element’s name. The first letter is capitalized but the second letter is not.

Aluminum- Al Platinum- Pt Zinc- Zn

Element Symbols

The origin of some symbols, however, are less obvious.

The symbol for gold is Au. The symbol for lead is Pb. The symbol for iron is Fe

Symbols you need to know!!!

Pb-Lead Sn-Tin

Au- Gold Zn-Zinc

Symbols you need to know

Ni- Nickel Mn-Manganese

K- Potassium S- Sulfur

Symbols you need to know

Al- Aluminum Na- Sodium

O- Oxygen C- Carbon

Symbols you need to know

He- Helium Hg- Mercury

I- Iodine Ag- Silver

Symbols you need to know

Cu- Copper Fe- Iron

Ca- Calcium Cl- Chlorine

Symbols you need to know

Si- Silicon Mg- Magnesium

Ne- Neon Ni- Nitrogen

Symbols you need to know

B- Boron H- Hydrogen

John Dalton In the early 1800’s British scientist John

Dalton proposed that each element is made up of tiny particles called atoms.

Dalton stated that all of the atoms of a particular element are identical but are different from atoms of all other elements.

Daltons theory also assumed that atoms could not be divided into anything simpler. Scientist later found that atoms are made of even smaller particles.

The Structure of an Atom

A key discovery leading to the current model of the atom was that atoms contain charged particles. The charge is either positive or negative.

The structure of an Atom

Atoms are composed of three types of particles--- electrons, protons, and neutrons.

Proton- Positively charged particle. Inside the nucleus.

Neutron- An uncharged particle, Has the same mass as a proton. Inside the nucleus.

Electron- Negatively charged particles that move around outside the nucleus.

Atomic Structure: Electrons Atoms are extremely small. In fact, you could

fit millions of atoms in the period at the end of this sentence.

Electrons are much smaller than protons or neutrons. About 2000 times smaller.

They also move about the nucleus very quickly.

Negative electrons are attracted to the positive charged protons.

Atomic Numbers

The identity of an atom is determined by the number of protons in its nucleus, called the Atomic number.

Every hydrogen atom- atomic number 1- has exactly one proton in its nucleus.

Gold has 79 protons which means the atomic number is 79.

Atomic Mass Numbers The total number of protons and neutrons in

an atom’s nucleus is called its atomic mass number.

While the atoms of a certain element always have the same number of protons, they may not always the same number of neutrons, so not all atoms of an element have the same atomic mass number.

These are called isotopes.

Chlorine isotopes

Isotopes

You can find the number of neutrons in a particular isotope by subtracting the atomic number from the atomic mass number.

Atomic Mass

The atomic mass of the atoms of an element is the average mass of all the element’s isotopes.

Mendeleev

Russian Chemist: Dmitri Mendeleev

Arranged elements based on their physical and chemical properties. He arranged them in rows on a chart.

In 1869 he produced the first periodic table of elements.

Mendeleev

Mendeleev left some empty spaces where no known elements fit the pattern. He predicted new elements would be discovered.

He even described some of the properties of the unknown elements. Six years after the periodic table was published an element, aluminum, was discovered that matched some of Mendeleev’s descriptions!

Periodic Table

We call it the periodic table because it shows a periodic, or repeating pattern of properties of the elements.

The background colors of the square indicate whether the element is a metal, nonmetal, or metalloid.

Reading the Periodic Table1. The number at the top of the square is the atomic

number- the number protons in an element.

2. The chemical symbol is an abbreviation for the element’s name

3. The name of the element is written below the symbol

4. The number below the name indicates the average atomic mass of all the isotopes of the element

The Periodic Table (p. 148-149)

1. The color of the element’s symbol indicates the physical state of the element.

White letters indicate a gas Blue letters indicate a liquid Black letters indicate a solid

Groups

Elements in a vertical column of the periodic table show similarities in their chemical and physical properties.

Columns are known as groups Example: Halogen group: Combine easily

with many other elements and compounds. Example: Some metals react violently with

water and are all located in the same group.

Period

Each horizontal row in the periodic table is called the period.

The chemical properties of the elements show a progression

Atomic size decreases as you travel across the periodic table.

Review

Q: What are the particles that make up an atom?

A: Protons, neutrons, and electrons

Review

Q: The atomic number of potassium is 19. How does potassium-39 differ from potassium-41?

A: Potassium-41 has two more neutrons.

Review

Q: How is the modern periodic table organized?

A: By the atomic Number

Review

Q: What information about an atom’s properties can you read from the periodic table.

A: The number of protons in an atom’s nucleus, the average mass of one atom of that element, the element’s symbol, and the elements name.

Review

Q: Would you expect strontium (Sr) to be more like potassium (K) or bromine (Br)?

A: Potassium, because it is closer on the periodic table

Now We Are Ready for the Atomic Cookie Activity!

Section 5.3 The Periodic Table is a Map of Elements

Objectives: Classify elements as metals, nonmetals, and

metalloids. Identify different groups of elements. Describe radioactive elements.

How Are Elements Different?

Each element is located in a different part of the periodic table, and each has a very different use.

http://www.dayah.com/periodic/

Periodic Table has distinct Regions!

The Periodic Table is like a road map. Just as a map shows you where your going,

an atoms position on the periodic table indicates the properties of an element.

The Periodic table has 3 main regions: Metals on the left Nonmental on the right (except- H) Metalloids in between

The Periodic Table

An element’s position in the table also indicates how reactive it is.

Reactive indicates how likely an element is to undergo a chemical change.

Atoms in Groups 1 & 7 are the most reactive. Elements in Group 8 are the least reactive.

Most Elements are Metals

Metals are elements that conduct electricity and heat well and have a shiny appearance.

They can also be shaped by bending or being drawn into a long wire. Except for Mercury, Hg. Mercury is a liquid at room temperature. Most metals are solid at room temperature.

Reactive Metals

Group 1: Alkali Metals are extremely reactive. In fact, Sodium and Potassium are usually

stored in oil, to keep them from reacting with air. When exposed to air these elements react rapidly with oxygen and water vapor.

The ions of these metals are important for life, and play an essential role in the functioning of living cells.

Reactive Metals

Group 2: Alkaline Earth Metals are less reactive than the Alkali metals.

Calcium ions are an essential part of your diet.

Magnesium is a light, inexpensive metal that is often combined with other metals and used in airplane frames.

Transition Metals The elements in Groups 3-12 The earliest known elements: Cu, Au, Ag,

and Fe. Generally less reactive than other metals. This is why Gold and Silver are easily shaped

and used for jewelry. Ancient artifacts made from transition metals

can be found, remained unchanged. You can even find transition metals in foods

you eat!

Transition Metals

The properties of transition metals make them very important to industries.

Iron used to make steel- bridges and buildings

Copper used to make electrical wire Many are important for modern technology

Incandescent light bulbs made of tungsten Platinum is used in catalytic converters

Alloys

Two or more metals combine to form an alloy.

Alloys can be stronger, less likely to corrode, and easier to shape than pure metals.

Example: Steel- contains iron, nickel, chromium, and manganese.

Rare Earth Metals

Found in the top row of the rows of metals outside the main body of the periodic table.

Known as lanthanides because they follow the element lanthanum on the table.

Called Rare Earth Metals because scientist once thought they were only found in tiny amounts on Earth. Eventually scientist learned that they are not SO rare, but they are hard to isolate in pure form!

Rare Earth Metals

More and more uses are being found for the rare earth metals.

Europium, Eu, is used as a coating for television tubes.

Praseodymium, Pr, provides a protective coating against harmful radiation in a welder’s helmet