The periodic table is made of elements◦ What are elements?
Pure substances that cannot be broken down into simpler substances
Protons (+):◦ Positively charged◦ Same as the atomic number
Neutrons (neutral)
Electrons (-) ◦ Negatively charged
Each element is made up of:
1850’s: there were 58 known elements◦ Today there are 112!
◦ Scientists tried to organize elements
Atomic mass: the average mass of an atom of an element
The Periodic Table
Russian chemist He wrote down information about elements
on cards and put elements with similar properties in columns.
Dmitri Mendeleev
When Mendeleev arranged elements in order of increasing atomic mass, he found that some properties were similar!
He left some gaps in the table for elements that he thought would eventually be there based on properties.
Putting Elements in Order
By about 1915, the periodic table became based on a special number for each element, called its atomic number:◦ Is the number of protons an element has in its
nucleus.
All atoms are neutral◦ Their positive and negative charges balance◦ SO, atoms contain an equal number of electrons
and protons
The total number of protons and neutrons in an atom.
# of protons + # of neutrons = mass number
How do we find the number of neutrons?
Mass Number:
Mass number – atomic number = # of neutrons
Let’s do some!!How many neutrons do the following elements
have? a. magnesium b. nitrogen
c. argon d. copper e. hydrogen
Each element has a symbol of 1-2 letters◦ Ex: Ag – silver, H - hydrogen
Elements are commonly named after the people who have discovered them◦ Ex: Einstein- Einsteinium
Element Symbols
Fill in the following table:
Element Name
Element Symbol
#of Protons # of Electrons
# of Neutrons
carbon
O
16
aluminum
34
lithium
Ne
79
barium
http://www.youtube.com/watch?v=GFIvXVMbII0
The Periodic Table
GROUPS/FAMILIES: (1-18)◦ VERTICAL◦ UP and DOWN◦ Usually have common properties
PERIODS: (1-7)◦ Horizontal◦ LEFT TO RIGHT
How is it organized?Groups and Periods
LABEL
Separates metals from non-metals.
The elements touching the staircase: These are called METALLOIDS.
◦ Have properties of both metals and non-metals◦ Few in number◦ Solids
The “Staircase”
LABEL
Good conductors of heat and electricity
Bright metallic shine (lustre)
Easily shaped (malleable)
Solids (except mercury)
Poor conductors of heat and electricity
Dull, various colours
Brittle Solid or gas
(except bromine)
METALS vs. NON-METALS
Metals in the periodic table that run from Group 3 to the staircase.
Metal properties
Transition Metals
Except for hydrogen Most reactive
◦ Require special storage Why?
◦ Each alkali metal has an unpaired electron and tends to get rid of the electron by forming a compound
List them!
http://www.youtube.com/watch?v=m55kgyApYrY
Group 1- Alkali Metals
LABEL
Similar to group 1, but they are not as intense
Ex: magnesium reacts with water but less vigorously than sodium does.
List them!
Group 2- Alkaline Earth Metals
LABEL
Very un-reactive – INERT Is a useful property when it comes to light
bulbs!◦ Argon is commonly used inside a light bulb to
keep the tungsten from burning out Stable
◦ Do not have any unpaired electrons List them!
Group 18- Noble Gases
LABEL