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Elements
*organized on the Periodic Table of Elements
*periodic= occuring in a predictable pattern
The Ancient Beliefs 440 BC
They thought there were
4 elements:
•Fire
•Water
•Wind
•Earth
Elements
• are substances that cannot be changed into simpler substances by chemical reactions.
• There are about 118 elements found on Earth (only 92 occur naturally).
Starts with metals
Metals-Metalloids--Nonmetals- Noble Gases
An atomis the smallest part of an element
An atom is made up of:
Protons
Neutrons
Electrons
Key for the Periodic Table
CCarbon-------Element name
6 -------------atomic number
------Element symbol
12.011------atomic mass
Subatomic particlesparticle charge location Mass
(in amu’s)
Proton + In nucleus 1
neutron No charge In nucleus 1
electron negative In orbit around the nucleus
1/1836
Video on atoms-listen
An atom of Lithium
*The atomic # of Lithium must be 3
*The mass of an atom of Lithium MUST be 7. (4+3)
An atom of Sodium Na
• The atomic # of Sodium must be 11
• *The mass of an atom of Lithium MUST be 23. (11 + 12)
The atom and the Periodic Table
• The atomic # = the # of protons• The mass of the atom is:• (# protons) + (# of neutrons)• Assume the # of electrons = # protons
Drawing atoms:
• Let’s draw an atom of:
Carbon
• Let’s draw an atom of:
Fluorine
Atom comes from the Greek word
atomos
• Atomos in Greek means INVISIBLE
• Scientists used to think that the atom was NOT made of any smaller particles
• It wasn’t until 1897 that scientists realized that atoms are made up of smaller particles
Draw these on your own
• Helium
• Potassium
• Oxygen
• Hydrogen
Molecules and atoms
• Molecules are made up of atoms. Water is a molecule with 2 Hydrogen atoms and and 1 Oxygen atom.
• How many atoms are in:
• CO2
• H2O2
• O2
What are they?
Metals
• Good conductors of heat and electricity
• Good at giving up electrons
• Malleable and ductile• Lustrous
Non-Metals• Poor conductors
therefore, good insulators• Good at taking electrons• Brittle (break easily)
Nuclei of a Helium atom and of a Lithium atom