The Atom and

Periodic TablePhysical Science

Element verse Atom

• ELEMENT– A substance that

cannot be broken down into simpler substances

– Ex: Neon, Gold, Helium

• ATOM– Smallest particle

of an element–Counting unit of

elements

History of the Atomic ModelDemocritus

--believed in the atom

John Dalton--made the theory on

atoms

J.J. Thomson--found the electron

Ernest Rutherford--found the nucleus

History of the Atomic Model

Neil Bohr--established energy

levels

Electron Cloud Model--the current model of

the atom

3 Subatomic ParticlesAtoms can be broken into:

• Protons–Positively charged– Symbol = p+

–Mass = 1

• Electrons–Negatively charged– Symbol = e-

– Extremely small mass

• Neutrons– No charged (neutral)– Symbol = n–Mass = 1

Parts of an Atom• Nucleus– Center of the atom– Small, dense,

positively charged– Where Protons and

Neutrons remain

• Energy Levels/Shells/Orbitals– Around the nucleus– Contains the electrons

Atomic Number

• The Identify of the element

• Number of Protons• Top of the Element

Block• SECRET: Also the

number of electrons

Mass Number

• The sum of the Protons and Neutrons

• Bottom Number of the element block

• Round to the Nearest Whole Number

Understanding an Element BlockATOMIC NUMBER

Element Symbol1st letter is upper case2nd letter is lower case

Element Name

Mass NUMBER

How do you Find Items

• Number of Protons = Atomic Number

• Number of Electrons = Number of Protons– (Because Atoms are neutral which means positive equals negative)

• Number of Neutrons = Mass Number subtract Atomic Number

Electron, Protons, Neutrons Example Practice

Name Symbol Atomic Number

Mass Number

Number of Protons

Number of Electrons

Number of Neutrons

NEON

BORON

ISOTOPES• Atoms of the same

element that have the same atomic number but different mass numbers

• # of protons stays the same

• # of neutrons change

How Isotopes are Written

• Elements name/symbol dash mass number• Ex:–Oxygen—16 p+= n =

–Oxygen—17 p+= n =

–O—18 p+= n =

Why is Mass Number a Decimal?• Mass Number is the

weighted average of all the isotopes of an atom

• The isotope whom mass number is closest to the actual mass number is more abundant

IONS• Charged Particles–Negative Charge = gains electrons–Positive Charge = lose electrons

The Periodic Table• An arrangement of

elements in columns based on properties that repeat from row to row

• Modern Periodic Table arranged by Henry Moseley– Arranged by increasing

atomic number

Parts of the Periodic Table

• ROWS–Called Periods–Go across

• COLUMNS–Called Groups–Go up and down

Periods• 7 periods• Elements in the

same period have:–Same number of

energy levels or shells or orbitals

Groups• 18 groups• Elements in the

same group have the same:–Properties–Valence Electrons–Oxidation

Numbers

Valence Electrons• Number of electrons on

the outermost (last) energy level

• Code: – 1, 2, 3, 4, 5, 6, 7, 8

• Number next to “A” at the top of the column

Know Your Roman Numerals• I = 1

• II = 2

• III = 3

• IV = 4

• V = 5

• VI = 6

• VII = 7

• VIII = 8

Oxidation Number• Number of electrons an

atom will gain or lose to become stable

• Stable = 8 electrons on last shell

• Code:– +1, +2, +3, ±4, -3, -2, -1, 0

• “+” means lose electrons• “—” means gain electrons

Labeling the Periodic Table

Bohr’s Model

• Focuses On Electrons

• Places electrons into energy levels

• Developed by Neil Bohr

Components of Bohr’s Model

Circles• Number of

Circles = Period Number = Number of Energy Level

DOTS• Go on the Last Circle• Number of Dots = Number

of Valence Electrons

• Important Note– First energy level has a max

of 2 electrons– All other energy levels have

a max of 8 electrons

Steps to Draw Bohr’s Model1. Place a dot to be

Nucleus

2. Place circles around Nucleus

3. Place dots on last circle in correct order

EXAMPLEOxygen

Bohr Model Practice

NEON Boron Helium

Electron Dot Diagrams• Model of an atom

in which each dot represents the valence electrons

• AKA: Lewis Dot Diagrams

Steps to Draw Dot Diagrams1. Identify the number of

valence electrons

2. Write the element’s symbol

3. Place dots around the symbol equal to valence electrons in correct order

ExampleNEON

Dot Diagram Practice

Fluorine Sodium Carbon

Classifying Elements• Elements are

classified as metals, nonmetals, or metalloids based on properties and location on the periodic table

Metals• Most elements are them• Good Conductors of

electricity/heat• Solid at room

temperature (except Mercury)

• Ductile: turn into thin wire

• Luster: reflect light

• Malleable: hammer into sheets

• High Melting Point• Left side of the stair step• Francium: Most reactive

metal• High Boiling Point

Nonmetals• Dull• Brittle• Poor Conductors of

electricity/heat• Most are gas at room

temperature• Low Melting Point• Low Boiling Point• Right Side of Stair Step• Fluorine: most reactive

nonmetal

Metalloids• Have BOTH

characteristics of metals and nonmetals

• Found on the stair-step line

• What are the Metalloids–B, Si, Ge, As, Sb, Te, Po,

At

Periodic Trend• Reactivity–As you go left to

right across a period, the less reactive elements become

THE FAMILIES AND GROUPS OF THE PERIODIC TABLE

Alkali Metals• Group IA

• 1 valence electron

• Reactivity increases from top to bottom

• Francium is most reactive metal

Alkaline Earth Metals

• Group IIA

• 2 valence electrons

• Ca: is in your bones, teeth, shells

Transitional Metals• THE MIDDLE OF THE

PERIODIC TABLE• Groups 3B-12B• Vary in oxidation

numbers• Brightly colored• Likes to combine

with Oxygen

BORON FAMILY

• Group IIIA

• 3 valence electrons

• Al: most abundant metal in Earth’s crust

Carbon Family• Group IVA

• 4 valence electrons

• Carbon is the element of life

Nitrogen Family• Group VA

• 5 valence electrons

• N is 78% of air

• Main component of fertilizer

Oxygen Family

• Group VIA

• 6 valence electrons

• O: most abundant element in Earth’s crust

The Halogens• Group VIIA

• 7 valence electrons

• Salt formers

• Reactive with metals

• Fluorine: most reactive nonmetal

Noble Gases• Group VIIIA

• 8 valence electrons

• Stable = not reactive

• Inert Gases

• All Shells are full