All matter are composed of atoms (microscopic particles)



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

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