Download Lesson 1_lesson2

Atoms Worksheet: Where we are at.
• Atom diagrams.
• Protons and neutrons located in the nucleus
with surrounding electrons located in
discreet energy levels or shells.
Review exercise 3.1
• In review exercise 3.1 we used the atomic number
(Z) and the mass number (A) to work out how
many protons, neutrons and electrons in neutral
atoms.
• Note: Elements are arranged in the periodic table
according to their atomic numbers (Z)
Definitions: You need to know
these!!!
• Atomic number (Z) = number of protons in
the atom.
• Mass number (A) = number of protons +
number of neutrons in the atom.
Isotopes
• Isotopes are atoms or the same element that have
different numbers of neutrons in the nucleus.
• As such their atomic numbers are the same but their
mass numbers differ.
Example Question:
Relative Atomic Mass
• As atoms are too small to be weighed easily. By convention we
use relative atomic masses to compare atoms.
• The modern standard atom is Carbon-12 which has a value of 12
Particle
Symbol
Mass (kg)
Relative
mass
Charge
(C)
Relative
Charge
Proton
p
1.673 x 10-27
1
1.60 x 10-19
+1
Neutron
n
1.675 x 10-27
1
0
0
Electron
e
9.110 x 10-31
~ 1/1840
1.60 x 10-19
-1
Practice Sheet: Isotopes and relative
atomic mass
Activity matching information to elements
Atoms Worksheet
• The other worksheet that you had for homework
discussed electron configurations.
• Electron configurations being the arrangement of
electrons orbiting the nucleus of an atom.
• Bohr’s work contributed the understanding that
electrons are located in energy levels or shells.
Electron Energy Levels
• In a neutral atoms the number of electrons is equal to the atomic
number of the atom.
• Electrons fill the shells closest to the nucleus first.
• The closer to the nucleus a shell is, the lower its energy level. The
shell closest to the nucleus can hold a maximum of two electrons.
The second shell out from the nucleus can hold a maximum of
eight electrons.
• The maximum number of electrons in each shell is determined by
the formula: 2n2
Energy level (n)
Energy level symbol
Max number of electrons
1
K
2
2
L
8
3
M
18
4
N
32
Question 4
• Question 4 of the worksheet asked you to:
-Draw an atom of the elements from
atomic number 1 to 20
- Answer some questions
Did anyone do this?????
• Use the diagrams on the next slide to do this
activity
Trends in electron configurations
• From this exercise we see the electrons filling the lowest
shells first. (K, Ca in row three is an exception to this
trend)
Electron Configurations
• Elements in row 1 going across the table
have electrons in shell 1. Elements in row 2
have electrons in shell 2 etc.
• Also we see that elements in the same group
(going down the table) have the same
amount of electrons in their outer valence
shells.
•Medeleev’s periodic table 1869
http://www.youtube.com/watch?v=nsbXp64YPRQ
What elements are missing from
Mendeleev’s table?
Why did Mendeleev’s table not
include the Noble gases.
• The noble gases located in group 8 of the periodic
table are extremely stable un-reactive elements.
• As such they were not discovered until 1895 by
Lord Rayleigh and William Ramsay
Intro to noble gases:
http://www.youtube.com/watch?v=QLrofyj6a2s
Nobel gas song:
http://www.youtube.com/watch?v=5KiTu4dWXik
Chemical reactivity of the elements.
• Whereas the unreactive nature of the noble gases
delayed their discovery, for other elements such as
gold the very same reason has meant that thi metal
has been known and used since 6000 BC
• Read 2.2 Jacaranda and do questions on page 48
• Look at
http://www.periodicvideos.com/videos/079.htm
• Reactivity of Rubidium:
• http://www.youtube.com/watch?v=m55kgyApYrY
Noble gases and the reactivity of
elements
• The reluctance of the noble gases to react chemically is the key
that unlocks our understanding of why other elements do react.
• Unreactive Species: If an atom has the electron configuration of a
noble gas it will be chemically unreactive, or only react with
difficulty.
• Reactive Species: If an atom does not have the same electron
configuration as a noble gas, it will tend to react in order to
achieve this.
• The noble gases are unreactive, because their outer electron shells
are full. A full shell of outer electrons is a particularly stable
arrangement. This means that noble gas atoms neither gain nor
lose electrons easily; they react with other atoms with great
difficulty, or not at all.
Formation and naming of simple
ions
Nobel gas song:
http://www.youtube.com/watch?v=5KiTu4d
WXik
• http://www.youtube.com/watch?v=CV53wf
l-oV8 10 min
• Worksheet: Electron configuration and
valency
Charge on ions and common
polyatomic ions.
• Read p 18-19 surfing scientist
• Students to answer the questions
Ionic and Covalent bonds