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Chemistry - elements and the periodic table - Coggle Diagram
Chemistry - elements and
the periodic table
Scientists
Robert Boyle:
discovered "an element is a substance that cannot be broken down into smaller substances by chemical means. :
Humphrey Davy:
discovered
potassium and sodium
(electrolysis - broke down water into hydrogen and oxygen)
Henry Moseley:
measured atomic number
Dobreiner:
saw trends among triads
John Newlands:
tried to find a mathematical relation between atomic weights of chemically similar elements
Groups:
octaves
Arranged the elements in rows of seven
Eight element has similar properties to the first
Errors:
no gaps were left for undiscovered elements
Dmitri Mendeleev:
suggested that properties of elements were
function of their atomic masses
Left gaps for undiscovered elements
Predicted properties of undiscovered elements
Periodic table
List of elements arranged to demonstrate trends in phyical and chemical properties
Ordered by atomic mass
Periods:
rows
Groups:
columns
Period number:
the highest unexcited energy level for an electron in that element
BAT staircase: seperates metals and non metals
M.A.N:
mass - atomic = neutrons ex. O2 (16 - 8 = 8)
Atom:
smallest part of the element that retains properties of that element
Atomic number:
number of protons
Protons = electrons
Atom = neutral
Ion = charged atom
(+) cation (-) anion
Groups:
elements that share several common properties
Same outer electron arrangement
Outer electrons:
valence electrons
Number listed above group:
usual number of valence electrons
Group 7:
Halogens ex. Chlorine and Iodine
Bleach, disinfectans and salts
Non metals
Highly reactive
Varying physical properties
React with hydrogen to form oxides
Chlorine
Green gas
Chlorine + hydrogen = hydrogen chloride gas
Hydrogen chloride gas dissolves in water to form hydrochloric acid
Chlorine reacts with sodium to form sodium chloride (table salt)
Protons = 17 Electrons = 17 Neutrons =18
Position of element
= number of shells ex. Cl = period 3; 3 shells
Group 8:
Noble gases ex. Helium and Neon
Make lighted signs, fridges and lasers
Not reactive
Little tendency to lose or gain electrons
Transition metals
Groups 3 - 12
Very hard
High melting and boiling points
Good electrical conductors
Metals
Good conductors of heat and eletricity
Group 1:
Alkali metals ex. Sodium and Potassium
Form salts and other compounds
Less dense than other metals
Highly reactive: reactivity increases as you move down the group
React with water to form hydroxides
Burn in air to form oxides
(metal + oxygen)
Sodium
Sodium + oxygen = sodium oxide
Sodium + water = sodium hydroxide and hydrogen gas
Stored in water to prevent reactions with air and water
Group 2:
Alkaline earth metals ex. Calcium and Magnesium
Form many compounds
Reactive
Burn in air to form oxide
React with water to form hydroxides
Lustrous and malleable
Flame test
(Li, Na, K, Ba, Sr, Cu)
Theory:
different colours are given off when salts of certain metals are heated. The colours can be used to identify the metals present.
Sodium = yellow / orange
Street lights
Potassium = lilac / violet / purple
Copper = green-blue / blue
Lithium = deep red
Fireworks
Strontium = red
Fireworks
Barium = yellow-green
Why does this happen?
The energy differences between energy levels in metal atoms vary. Using energy from the flame, electrons in the atoms move to higher energy levels and then return to lower energy levels. This emitts light
Procedure
Using clean / description of cleaning//
Platinum (nichrome) / soaked (dipped) //
Wire (probe) / splint (lollipop stick)
Dip wire (splint) into salt //
Place salt in (into, on, at edge of, at top of) flame //
