Transcript Powerpoint - Valence Electrons

Chapter 2 – Elements and
The Periodic Table
Elements
• Element – a type of matter made up of only one
kind of atom (e.g. periodic table).
• Atom – smallest particle of an element that still
retains all the properties of that element.
• Compound – 2 or more elements joined (e.g.
H2O).
• Molecule – 2 or more atoms combined (e.g. CO
carbon monoxide; O2 oxygen gas).
Symbols Off the Periodic Table
•
•
•
•
The symbols on the Periodic Table are universal (used world-wide)
Symbols come from Latin (or Greek) words
CAPITALIZE the first letter
Lower case 2nd letter (if it is needed) e.g. No vs. NO
Who created the Periodic Table?
Section 2.2
• Born : 1834
Died : 1907
Nationality : Russian
Occupation : Chemist
• Dmitri Mendeleev brought
order to the chaos of
chemistry by asserting his
periodic law, which states
that the elements arrange
themselves according to
their atomic number and
their chemical properties.
How is the Periodic Table set up?
• Elements are listed horizontally according to
their atomic number (number of protons).
• Periods are the horizontal rows of elements.
• Elements are listed vertically according to their
chemical properties.
• Groups or Families are arranged vertically.
Alkaline
Earth
Alkali
Metals
Metals
Groups
Halogens
Noble
Gases
Atomic Number and Atomic Mass
• Atomic number =
number of protons
found in the nucleus.
– Ex. Oxygen’s
atomic number is 8
• Atomic mass = mass
of an average atom of
an element.
Measured in atomic
mass units (amu)
Atomic number
Symbol
Atomic mass
Alkali Metals
• Highly reactive
– Reactivity increases as you go down the
group.
•
•
•
•
•
Metals
React with both oxygen and water.
Soft
Low melting points
Have a +1 ion charge
Alkaline Earth Metals
•
•
•
•
Less reactive than alkali metals
Metals
Burn in air if heated
Produce bright flames and used in
fireworks.
• Will react with water, but not as vigorously
as alkali metals
• Have a +2 ion charge
Halogens
•
•
•
•
•
•
Non-metals
Highly reactive
F and Cl are gases at room temperature
Br is a liquid and I is a solid
F is the most reactive and I is the least
Have a -1 ion charge
Noble Gases
•
•
•
•
•
•
Most stable and unreactive elements
They are colourless, odourless gases
Ar and Ne are used in light fixtures
Non-metals
“Royal”
Have a 0 ion charge
Metals, Non-metals, and Metalloids
Table 2.2 - Properties
State at
Room
Temperature
Appearance
Conductivity
Malleability
and
Ductility
Metals
- Solid except
Mercury
- shiny luster
- good conductors of
heat and electricity
- malleable
- ductile
Non-metals
- some gases
or solids
-bromine is a
liquid
- not very
shiny
- poor conductors of
heat and electricity
- brittle
- not ductile
Metalloids
- solids
- can be shiny
or dull
- may conduct
electricity
- poor conductors of
heat
- brittle
- not ductile
Section 2.3 - Electron Shells:
3-D Outside the Nucleus
• The way an element
chemically reacts depends
on the number of electrons
in it’s outer shell.
• Atoms are stable when their
outer shells are full of
electrons.
• If a shell is not full, the atom
is reactive, and it either
wants to fill its outer orbital or
get rid of it altogether.
Shell
(orbital)
Maximum
# of e-
1
2
2
8
3
8
4
18
Just use this table for
our purposes in grade 9
Bohr Model Diagrams
• It has 8 e- in outer
shell.
• Doesn’t react!
• Noble Gas
Look at the outer shell.
Examples when outer shell is not full
Look at the outer shell of each:
– Outer shells not full.
– Reactive!
Lithium
Lithium will donate 1 eand Fluorine borrow 1 eFluorine
Valence Electrons
• Valence electrons are found in the outermost
shell.
• Most elements in the same family have the
same number of valence electrons
Examples:
Halogens = seven valence electrons
Alkali = one valence electron
Alkali Earth metals = two valence electrons
Noble Gases - are stable and non-reactive
because they are full in the outer most valence
shell.
Bohr Models of the First 18
Elements
Ion Charge or Combining Capacity
• The ion charge is an electric charge that forms
on an atom when it gains or loses electrons.
• Any electrically charged atom is called an ion.
• If an atom has gained electrons, it will be
negatively charged.
– Usually non-metals
• If an atom has lost electrons, it will be
positively charged.
– Usually metals