ATOMS AND THE PERIODIC TABLE

chapter three

FOCUS ACTIVITY 1

METAL USE PROPERTY

Copper Money durable

ATOMIC THEORY - history

4TH CENTURY B.C.

Matter is made of tiny particles called ATOMS.

John DALTON

ELEMENTS are made

of particles called atoms.

ATOMS of the same

elements are alike.

ATOMS form molecules.

EARLY 1900’s

(1913)

ELECTRONS orbit like planets in the solar system.

MID 1900’s (after 1925)

Modern theory

ATOMIC THEORY - STRUCTURE MODEL OF THE ATOM

ELECTRON -

NUCLEUS

PROTON +

NEUTRON (NEUTRAL)

ENERGY LEVELS

ATOMIC STRUCTURE ELECTRON LOCATION

Electrons are found in energy levels of an atom.

Electrons occupy the lowest energy level available.

Bohr’s Atom and Energy Levels

Energy Levels are like ladder rungs…

GOOD BETTER

GAINING ENERGY

Energy Levels

ORBITALS – where the _____ are located within an energy level.

S orbital

(Like a sphere)

may contain up to 2 electrons

first energy level is an s orbital

1s and 2s orbitals

P orbital

(Like a dumbbell)

may contain up to 2 electrons

second energy level may contain an s orbital and up to 3 p orbitals

Orbitals

_____ electrons are located in the outermost energy level of an atom.

They determine the chemical properties of an element.

3.2 A TOUR OF THE PERIODIC TABLE

• Properties of elements change in a regular pattern that the table helps to describe.

• Periods –

• Groups(families) -

Los Alamos National Laboratory: Periodic Table

Traditional Periodic Table

A Spiral Vision of the Periodic Table of the Elements

The number of protons in an atom determines an element’s location on the table.

Los Alamos National Laboratory: Periodic Table

6

C

Carbon

12.001

ATOMIC NUMBER

SYMBOL

NAME

MASS

PROTONS

(and ELECTRONS too)

PROTONS

+ NEUTRONS

MASS #

11

1800 1

PROTONS AND NEUTRONS HAVE EQUAL MASS.

ELECTRONS ARE TINY – 1800 EQUAL ONE PROTON.

MASS 35

ATOMIC NUMBER 17

protons _?_ electrons _?_

neutrons _?_

Cl

IONS are atoms that have lost or gained an ___.

• ELECTRON GAINED =

NEGATIVE CHARGE

(-)

ELECTRON LOST =

POSITIVE CHARGE

(+)

Na+Cl

Electron

transfer

TWO KINDS OF IONS:

A (+) CHARGED ION IS A ____.

A (-) CHARGED ION IS AN ___.

EXAMPLES:

• LITHIUM

• FLUORIDE

The atoms of an element always have the same number of protons.

BUT…..The atoms of an element may have

different numbers of neutrons.This is an ISOTOPE!

Two carbon ISOTOPES:

CARBON 12 = 6 protons and 6 neutrons

CARBON 14 = 6 protons and 8 neutrons

The AVERAGE MASS of an ATOM• Why is the mass number not an even

number?– Atoms of the same element exist with

different numbers of neutrons.– This makes the mass of different atoms of

the same element different.– The average mass is a weighted number so

that more common isotopes have a greater affect on the average than rare isotopes.

• What is an amu?– It is an “atomic mass unit”.– An amu is equivalent to the mass of 1/12 of

a carbon-12 atom.

3.3 FAMILIES OF ELEMENTS:

• HAVE THE SAME VALENCE NUMBER.

• HAVE SIMILAR CHEMICAL AND PHYSICAL PROPERTIES.

• A COLUMN OF ELEMENTS IS A FAMILY.

TWO MAJOR DIVISIONS• METALS • NONMETALS

GROUP ONE:ALKALI METALS

• VERY REACTIVE• ONE VALENCE

ELECTRON

                         

        

GROUP TWO:ALKALINE EARTH METALS

• TWO VALENCE ELECTRONS

GROUP 3-12:TRANSITION METALS

• MANY COMMON METALS

• NOT AS REACTIVE AS OTHER METALS

GROUP 17:HALOGENS• VERY REACTIVE

• FORM SALTS WITH ALKALI METALS

• 7 VALANCE ELECTRONS

GROUP 18:NOBLE GASES

• INERT / UNREACTIVE

• EIGHT VALENCE ELECTRONS

SYNTHETIC ELEMENTS• They are man-made and radioactive.• They include all elements above #92, plus #43

and #61.

SEMICONDUCTORS (METALOIDS).

The elements that are between the metals and nonmetals are known as:SEMICONDUCTORS (METALOIDS)

They may exhibit metallic and nonmetallic properties.

B

Si

Ge As

3.4 USING MOLES TO COUNT ATOMS• Some counting units:

– Reams of paper– Dozens of eggs– Atomic mass units of protons and neutrons– Moles of atoms

• A mole is the SI unit that describes the amount of a substance.

• Avogadro’s constant is the number of particles in one mole which = 6.022 x1023

• molar mass is the mass in grams of one mol of a substance…it is equal to the average atomic number of an atom.

• Vocabulary

• Parts of an atom

• History

• Element families

• Using the periodic table

• Metal vs. nonmetal

Chapter 3Studying for the Test