all matter are composed of atoms (microscopic particles)
to form a line 1 mm long 4 million of the largest atoms are needed
basic types of atoms are called elements
there are 118 elements
examples of elements: oxygen, silicon, aluminum, copper, iron, calcium, gold, silver
each element has a unique set of chemical and physical properties that distinguish it
from all other elements
Symbols of elements
each element has a unique symbol that is internationally recognized
symbol of an element consists of one to three letters
element
symbol
oxygen
O
silicon
Si
aluminum
Al
copper
Cu
iron
Fe
calcium
Ca
gold
Au
three letter symbols are used for newly discovered unnamed elements
first letter of the symbol is always capitalized or uppercase; next letter is lowercase
***it is easy to see where the symbols for oxygen, silicon, aluminum and
calcium came from
symbols can come from
first letter of the name (e.g., oxygen)
first letter of the name plus the next letter (e.g., , silicon, aluminum and calcium)
first letter of the name plus a later letter in the name
magnesium
Mg
chlorine
Cl
zinc
Zn
plutionium
Pu
other symbols for elements came from the Latin name
Latin was the language of many early chemists
Cu
cuprum
Fe
ferrum
Au
aurum
other symbols for elements came from the German name
W
wolfram (German word for tungsten)
names of elements
1. some elements have been named in honor of a person
Seaborgium
from Glenn Seaborg, an American chemist and Nobel Prize winner
who helped isolate and identify elements 94 -102
Einsteinium
from Albert Einstein
Curium
from Marie and Pierre Curie who first discovered radioactivity
2. some elements have been named after places
americium
(the America)
europium
(Europe)
californium
(California state)
berkelium
(Berkely, California)
francium
(France)
3. some elements have been named after the planets
plutonium
(planet Pluto)
neptunium
(planet Neptune)
uranium
(planet Uranus)
Hydrogen - most common element
more than 90% of the atoms in the known universe are hydrogen atoms
living things are composed primarily of four elements C, H, O, N
in 1750 only 16 elements were known (e.g., gold, carbon, copper, iron, lead,
mercury, platinum, silver)
elements may exist as single atoms or as molecules
e.g., Helium, used to fill balloons exist as individual atoms (monoatomic)
molecule - consist of two or more atoms in a definite ratio (generally composed of
non-metals only)
- may consist of two or more atoms of the same elements or
atoms of different elements
Nitrogen, N2 is diatomic
diatomic means each molecule contains 2 atoms of the same type
other diatomic molecules are H2, O2, and the halogens
other elements which exist as molecules
P4, S8
some elements have allotropic forms
allotrope - one of a number of different molecular or crystalline forms
of the element
oxygen has two allotropes
O2 gas that we breathe
O3
ozone, toxic
produced by electric discharge through air
you can smell ozone when separating clothes stuck together by “static cling” or
after an intense thunderstorm
carbon has four allotropes
1. graphite - soft gray solid with slippery texture
2. diamond - hardest substance on Earth
3. buckyball - 60-C molecule
4. buckytube