Ceiling Periodic Table

7 05 2012

There are many clever ways of incorporating chemistry into your daily life, from periodic puzzles and periodic cups to building plastic molecular models (a favourite of mine), and even periodic cupcakes, but this ceiling seems a nice interactive idea!

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Lesson 2

3 05 2012

Click this link to download: Lesson 2: Atomic Structure, Isotopes and Electronic Configuration

Objective: To understand the basics of atomic structure, Isotopes and electronic configuration.

Atomic Structure

Atoms are made up of sub-atomic particles called protons (+), neutrons (0 hence being neutral) and electrons (-).

Particles Mass Charge
p 1 +1
n 1 0
e 0 -1

Example:

7

   Li

3

In Lithium there are 3 protons, 3 electrons, and 4 neutrons.

The number below the elemental symbol (in this case 3) is the atomic number; this indicates the number of protons in the nucleus of the atom.

The number above (in this case 7) is the atomic mass number; this represents the number of protons + the number of neutrons.

We already know from the atomic number that the number of protons is 3, so if we subtract 3 from 7 we are left with the number of neutrons, 4.

Remember: the number of protons = the number of electrons

(If we assume the element to be electrically neutral, or uncharged. If dealing with questions regarding charge, ions etc, then further considerations would need to be made.)

Test yourself:

39

     K

19

p = ?

n = ?

e = ?

(See answers at the end of this document)

Isotopes

These are atoms of the same element that have the same atomic number, but different mass number.

In other words, Isotopes have the same amount of protons but a differing amount of neutrons.

Example:

35                        37

     Cl                         Cl

17                        17

n = 18                 n = 20

Both Isotopes of Chlorine have 17 protons (and electrons), but as you can see a different amount of neutrons.

Electrons exist around the nucleus of atoms in different energy levels called electron shells, of which there are several.

Sticking with Chlorine, we see that its 17 electrons are spread throughout the layers of electron shells that make up an atom of this element.

The centre is of course the nucleus, where protons and neutrons reside, and the grey dots surrounding it are the electrons.

Those nearest to the nucleus are in the first shell, moving out one is the second shell, and the outer third shell.

In the first shell there are 2 electrons, in the second shell there are 8 electrons and in the third outermost shell there are 7 electrons (hence 2, 8, 7). It is important to know how many electrons each shell can physically hold; as there is a reason every element follows these basic rules, so onto our next heading….

Electronic Configuration

The way in which electrons are arranged within an atom.

Shell

name

Subshell

name

Subshell

max

electrons

Shell

max

electrons

K

1s

2

2

L

2s

2

2+6=8

2p

6

M

3s

2

2+6+10

=18

3p

6

3d

10

N

4s

2

2+6+

+10+14

=32

4p

6

4d

10

4f

14

http://en.wikipedia.org/wiki/Electron_shell

As you can see each shell has a sub-shell, with shell 2 being made up of 2s and 2p, shell 3 being made up of 3s, 3p and 3d. Each sub-shell has a limit Read the rest of this entry »





Lesson 2: Atomic Structure, Isotopes and Electronic Configuration

3 05 2012

Click the link below to download the Lesson, it is a Word Document file.

Lesson 2

If there are any problems downloading, or general questions/thoughts, don’t hesitate to comment.





Chemistry Lesson 1: Periodic Trends

3 05 2012

Click the link to download this lesson: Lesson 1: Periodic Trends

I wrote this to help remember the basics of periodic trends. These are basic but important for science A Level revision.

Click the link at the top and feel free to download the Word Document, leave a comment 🙂

Image courtesy of Wikipedia

Atomic radius

The distance from the atomic nucleus to the outermost stable electron orbital in an atom that is at equilibrium.

↓ Increases down a group (column of the periodic table)

←  Increases across a period (row of the periodic table) from right to left

Therefore atomic radii are largest in the bottom left corner of periodic table.

e.g. Ce is the largest, and Fr has a larger radius than He.

Why does atomic radius decrease as you go across a period? (from left to right) →

The effective nuclear charge increases → therefore attracting the orbiting electrons towards the nucleus and lessening the radius. Less distance between the electrons and the nucleus so the nuclei pull is stronger.

(See bottom of this post for more information on effective nuclear charge.)

Why does atomic radius increase as you go down a group?

The addition of a new energy level (shell)

Ionisation Energy

 This is the energy required to Read the rest of this entry »