CHEMISTRY UNIT 2 THE STRUCTURE OF THE ATOM AND THE PERIODIC TABLE

CHEMISTR

Y UNIT

2THE S

TRUCTURE OF

THE ATOM

AND T

HE

PERIODIC

TABLE

STRUCTU

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THE A

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Nucleus Center of an atom Made up of:

Protons Positive charge

Neutrons Neutral charge

Electron Cloud Surrounds the nucleus Made up of:

Electrons Negative charge

THE STRUCTURE OF AN ATOM - TWO PARTS

Atom

NucleusCenter of

atom

Proton

Positive Charge

Neutron

Neutral Charge

Electron CloudSurrounds the

nucleus

Electron

Negative Charge

Positively charged

Atoms of the same element have the same number of protons.

atomic number

No two elements have the same atomic number.

Change # of protons? Different element

PROTONS

CHECK YOUR UNDERSTANDING

Element

Atomic

Number

Protons (p+)

1

Platinum

16

Fluorine

79

Calcium

Neutrally charged

Atoms of the same element may have different number of neutrons.

Mass Number Neutrons + Protons

Change # of neutrons?

Different isotope

NEUTRONS

Hydrogen

Most naturally occurring isotopes are stable

A few naturally occurring isotopes and all man-made isotopes are unstable

Unstable isotopes can become stable by releasing different types of particles.

Radioactive Decay

ISOTOPES

CHECK YOUR UNDERSTANDING

URANIUM

Mass Number 235

Atomic Number

Number of Neutrons 143

URANIUM

Mass Number 238

Atomic Number

Number of Neutrons

Negatively charged

Atoms of the same element may have different numbers of electrons

Atoms neutral unless stated otherwise

Charge

Change # of Electrons?

Ion

ELECTRONS

Electrons have energy kinetic Level

How Many Electrons Fit in the

Level

1 2

2 8

3 18

4 32

ELECTRON CLOUD

CHECK YOUR UNDERSTANDING

Atom/Ion Symbol

Atomic Number Protons Charge Electrons

17

I

12 10

19 +1

56 54

-1 36

8 -2

-3 18

ISOTOPE NOTATION

How many protons?

How many neutrons?

How many electrons?

CHECK YOUR UNDERSTANDING

REVIEW

Atom

NucleusCenter of

atom

Proton

Positive Charge

Change? New atom

Neutron

Neutral Charge

Change? New isotope

Electron CloudSurrounds the

nucleus

Electron

Negative Charge

Change? New ion

STRUCTU

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ARRANGEMENT OF

THE P

ERIODIC

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INFORMATION IN THE PERIODIC TABLE

Name of the Element

Symbol for the Element

Atomic Number: Number of protons

All atoms on the periodic table are neutral

Atomic Mass: The average mass of the isotopes of an element Protons + Neutrons

SYMBOLS

One or two letters that represent an element

Calcium is Ca1. First letter is Capital2. 2nd (& 3rd) letter is Lower case3. All letters are PRINTED only

STRUCTURE AND ARRANGEMENT

M E N D E L E E V

Grouped elements with similar properties.

Left gaps for what he assumed were undiscovered elements.

Periodic Law: Elements exhibited a periodic

recurrence of properties when arranged in order of increasing atomic mass.

C U R R E N T LY

Elements are arranged by increasing atomic number

Rows (Periods) Column (Groups) Families

Except Hydrogen

Better placed in group 7A. Some books place it

in both

ELEMENTS IN SAME GROUP SHARE SIMILAR PROPERTIES

TRENDS A

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PATT

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Roughly 80% of all elements

Located left of the stair-step line

All metals have similar properties

Good conductors Reactive Usually make positive

ions Easily combined to make

alloys

METALS

Located right of the stair-step line

All non-metals have similar propertiesGenerally poor conductors of heat and electricityAre good oxidizing agents (like rust)Form negative ionsSolid, liquid or gas at room temperature

NON-METALS

Touch the stair-step line

All properties between metals and non-metals

Often good Semi-conductors Electrical

conductivity between conductors (such as copper) and insulators (such as glass). 

METALLOIDS

ELECTRONEGATIVITY

An atom’s ability to attract electrons to itself

increases across periodsdecreases down groups

Size of an atomDecreases across periods Increases down groups

ATOMIC RADIUS

Similar properties in Groups/Families

PROPERTIES

Group 1 (except H)

All are shiny, soft metals

Highly reactive

ALKALI METALS

Group 2Highly reactive-

not as reactive as alkali

Very high melting point

Distinguishable by flame color

ALKALINE EARTH METALS

Group 17 Name means “salt formers” React with metals

to form saltsHighly reactive

HALOGENS

Group 18Stable/non-reactive

ColorlessOdorless

NOBLE/INERT GASSES

Group 3-12Very hardHigh melting/boiling points

High conductivity

TRANSITION METALS

Periods 6-7 Elements 57-71 and 89-103

Removed form main body of the table so it fits on a standard page

Actinides are all radioactive

Lanthanides bond with water

LANTHANIDE AND ACTINIDE SERIES

Group 13 is the Boron family

Group 14 is the Carbon family

Group 15 is the Nitrogen family

Group 16 is the Oxygen family

OTHER GROUPS