physical science 9 - a tradition of excellence since 1964 s/chapter 3.2.pdf · 0801 chapter 3.2 20...

0801 Chapter 3.2 1

Physical

Science 9 The Periodic Table

0801 Chapter 3.2 2

Physical

Science 9 The Periodic Table

0801 Chapter 3.2 3

Physical

Science 9 Atomic Structure

The Periodic Table groups elements together much like a grocery

store groups items in the same aisle.

Where is the Malt-O-

Meal you rebel scum!

0801 Chapter 3.2 4

2:00

0801 Chapter 3.2 5

Physical

Science 9

Simplified Periodic Table

See pages 78-79 in your text

0801 Chapter 3.2 6

Periodic Table with electron configurations

0801 Chapter 3.2 7

Standard Periodic Table

0801 Chapter 3.2 8

1:50

0801 Chapter 3.2 9


0801 Chapter 3.2 10


Symbol – A one or two letter

abbreviation for an element.

The first letter is ALWAYS

upper case.

Atomic Number – The

number of protons in the

atom. The periodic table is

arranged in proton order

from left to right.

Element name – The name of

the element.

Atomic Mass – The number of grams of one mole of the element (mass of

the element). Elements that have more protons generally have more mass,

therefore mass increases as you move from left to right.

0801 Chapter 3.2 11


You do NOT have to memorize data in the Periodic

Table. It will ALWAYS be available to you for tests and

homework.

The Periodic Table is your FRIEND!!!

0801 Chapter 3.2 12

Physical

Science 9 Other Periodic Tables

0801 Chapter 3.2 13

Physical

Science 9 Other Periodic Tables

0801 Chapter 3.2 14

The Periodic Table of the

Elements Created by an old Russian guy

named Dmitri Mendeleev in 1869.

He arranged the known elements of his

day in a table with each column

representing elements that had similar

chemical properties.

0801 Chapter 3.2 15


Elements

His original table included spaces for

elements that had not been discovered yet.

I was a genius of my time, and I

also had many, many bad hair

days.

0801 Chapter 3.2 16


Elements

Mendeleev’s Table had some problems,

but they pretty much eliminated when his

table was modified to list elements

according to atomic mass.

0801 Chapter 3.2 17 17:00

0801 Chapter 3.2 18

The Periodic Table

According to your book, there

are 92 naturally occurring

elements.

However, only 88 have actually

been found in nature. The

others have been synthesized

in labs or in atomic reactions.

Uranium (U, atomic number 92) is the heaviest naturally occurring

element. All of the heavier elements 93-118 were created in labs by

shooting a stable atom with protons hoping one will stick. Some of these

atoms exist only for nanoseconds before the extra proton is dumped.

0801 Chapter 3.2 19

Physical

Science 9 Electron Configuration

The electron configuration of an atom is a form of notation which

shows how the electrons are distributed among the various atomic

orbital and energy levels.

Orbitals are filled in a certain

order. Energy levels are not

filled one at a time – many times

the higher energy orbitals (d

and f) are skipped.

0801 Chapter 3.2 20

Physical


Example – Hydrogen has 1 electron. Using the chart below, it is

easy to see that the 1s orbital would be used to store this one

electron. Therefore, hydrogen’s electron configuration would be…

1s1

The first number is the energy

level of the atom where the

electron is.

The letter is the orbital that the

electron is in.

The exponent is the number of

electrons held in that orbital.

0801 Chapter 3.2 21

Physical


How about Helium? It has two electrons in each atom. The electron

configuration for Helium would be…

1s2

0801 Chapter 3.2 22

Physical


What about Oxygen? It has eight electrons in each atom. The

electron configuration for Oxygen would be…

1s2 2s2 2p4

If you add up all the exponents, it

should equal the number of

electrons

0801 Chapter 3.2 23

Physical


Let’s blow you away with a tough one. Let’s write the electron

configuration of Krypton.

1s2 2s2 2p6 3s2 3p6

4s2 3d10 4p6

0801 Chapter 3.2 24

Physical


0801 Chapter 3.2 25

0801 Chapter 3.2 26

0801 Chapter 3.2 27

Physical

Science 9 Electron Configuration Using the Periodic Table to do electron configurations

0801 Chapter 3.2 28

Physical

Science 9 Electron Configuration Shortcut Using Noble Gases

0801 Chapter 3.2 29

0801 Chapter 3.2 30

Physical

Science 9 Ions vs. Atoms

All atoms have a common goal…

It is the same goal that many of us have…

We want to have a fulfilling life…

Atoms want to be full as well…

It is each atoms goal to acquire EIGHT (8) electrons in

its outer energy level (there are a few exceptions

which we’ll cover later.)

0801 Chapter 3.2 31

Physical


As you remember from a previous discussion, the

outer energy level electrons are called valence

electrons.

As it turns out, the closer an atom is to having eight

valence electrons the more effort it has to attain that

goal.

Those atoms that are just one away from eight will do

almost anything to gain another electron…stealing is

their way of life…pillaging is their MO (modus

operandi)…

0801 Chapter 3.2 32

Physical


A chlorine atom has 7 electrons, and is

searching for one more to take from someone.

Along comes a sodium atom. The sodium atom

has only one valence electron. If it could get

rid of it, it would then have 8 valence electrons!

Sodium wants to get rid of

that one electron as much as

Chlorine wants to gain one,

so Sodium easily gives it up

and both atoms are happy!

However, they are not atoms

anymore…

0801 Chapter 3.2 33

Physical


Since the Chlorine atom

has added an electron, it

has also added an

additional negative

charge (remember,

electrons are negative).

So now the atom is not

electrically neutral

anymore…it has been

ionized! It is now an ion!

Since the Chlorine atom gained one negative charge, it’s overall charge

is -1. The Sodium atom has given up an electron, so its overall charge is

+1. This charge is called the VALENCE of an ion.

0801 Chapter 3.2 34

Physical


If an atom GAINS

electrons, it becomes

NEGATIVELY charged…

If an atom LOSES

electrons, it becomes

POSITIVELY charged.

0801 Chapter 3.2 35

Physical


If an atom LOSES electrons, it becomes POSITIVELY

charged…

…these ions are called

CATIONS

0801 Chapter 3.2 36

Physical


If an atom GAINS electrons, it becomes NEGATIVELY

charged.

These ions are called anions

0801 Chapter 3.2 37

Physical

Science 9 Octet Rule Exceptions

Hydrogen, Helium, Lithium, and Beryllium (the first

four elements) are happy with two valence electrons,

since the first energy level can only hold two

electrons, so it’s full!

0801 Chapter 3.2 38

Atomic number vs. Mass number

The ATOMIC NUMBER is the number of protons in the

atom.

The mass number is the number of protons and

neutrons in the nucleus.

The mass number of an atom can vary depending on

the number of neutrons. Atoms of almost any

element can have different number of neutrons.

0801 Chapter 3.2 39


Carbon, for instance, can commonly have 6, 7 or 8

neutrons in each atom.

They would be referred

to as C-12, C-13 or C-14.

0801 Chapter 3.2 40


When you look at the Periodic Table, you will notice

that Carbon has an atomic mass of 12.011.

If all of the Carbon atoms had 6 neutrons, the atomic

mass would be exactly 12.000.

But since there are

some C-13 and C-14

atoms mixed in, it raises

the atomic mass

slightly.

0801 Chapter 3.2 41


These variations in the number of neutrons are

called

ISOTOPES

So, C-12, C-13, and C-14

are isotopes of Carbon.

0801 Chapter 3.2 42

Calculating the number of Neutrons

To calculate the number of neutrons any atom has,

take the mass number and subtract the atomic

number (the number of protons).

C-14 has a mass

number of 14, with an

atomic mass of 6.

14-6 = 8 neutrons

0801 Chapter 3.2 43

Deathly Isotopes

Many isotopes are harmless. The water you drink

everyday contains isotopes of both hydrogen and

Oxygen (H-1, H-2, O-16, O-17 and O-18.

Isotopes that are

radioactive (give off

energy as they decay)

are dangerous and can

damage living cells.

0801 Chapter 3.2 44

0801 Chapter 3.2 45

Mass of a Single Atom

The mass of a single atom is extremely small.

Units like grams, pounds, and ounces are way too

big for the mass of an atom.

Scientists came up with a unit that can be used

with atoms. It is called the Atomic Mass Unit.

It is defined as 1/12th the mass of a Carbon-12 atom.

Since Carbon-12 has 6 protons and 6 neutrons, and

since electrons contribute very little to the overall

mass, it can be assumed that each proton and

neutron have a mass of 1 AMU.

0801 Chapter 3.2 46

Avogadro’s Number

So where do the atomic masses found in the Periodic

table come from?

Scientists came up with a quantity

unit called the moles. 1 mole = 6.02

x 1023.

This number was named after a

funny-looking Italian scientist,

Lorenzo Romano Amedeo Carlo

Avogadro. We call it Avogadro’s

number.

0801 Chapter 3.2 47

Avogadro’s Number

If you take 6.02 x 1023 atoms (1 mole) and place them

on a scale, you would come up with the atomic mass.

6.02 x 1023 is a BIG number.

If you had a mole (6.02 x

1023) of coke cans, they

would cover the entire

surface of the Earth with a

depth of 200 miles.

0801 Chapter 3.2 48

Avogadro’s Number

However, when you’re talking about something as

small as atoms, a mole of copper atoms would fit in a

tablespoon.

0801 Chapter 3.2 49

That’s All Folks

physical science 9 - a tradition of excellence since 1964 s/chapter 3.2.pdf · 0801 chapter 3.2 20...

Documents