“If I have seen further, it is by standing on the shoulders of giants.” Isaac Newton
What does this mean to you?
Greek Philosopher’s contribution
4 Elements of matter
matter is made of atoms (cannot be further divided)
Earth Fire Air Water
Alchemist believed that all matter was made of a limited number of elements.
Elements are basic substances that cannot be broken down into simpler forms by ordinary means.
92 exist in nature -
20 synthetic -
Atoms were tiny particles that could not be divided
Each element had its own kind of atom
John Dalton proposed that an atom is a sphere of matter that is the same throughout.
Came up with the idea of the electron – negatively charged particle
J.J. Thomson discovered that all atoms contain electrons, which are tiny, negatively charged particles. Thomson proposed that an atom is a sphere of positive charge. The electrons are mixed uniformly in the sphere.
Clay with embedded
He hypothesized that almost all the mass and all the positive charge of an atom is concentrated in an extremely tiny nucleus at the center of the atom.
Thought electrons traveled in fixed paths around the nucleus called energy levels.
Electrons are in random orbits around the nucleus
Electrons move rapidly throughout the atom
Energy Levels Still Exist
Electrons in Energy Levels 2 e - 8 e - 18 e - 32 e -
Arrangement and number of sub-atomic particles
Center or core of an atom
Contains 99.9% of the weight of an atom
Contains protons and neutrons
Occupies 1 / 100,000 of the space of an atom
Positively Charged Sub-atomic particles
Found in the nucleus
All protons are a like
Weight of 1 proton =
1 atomic mass unit
Neutrally charged (no charge) sub-atomic particle
Atomic weight of 1 atomic mass unit
Found in nucleus
The Number of Protons in the nucleus.
What makes atoms different?
Atomic number is the number of Protons in an atom
All atoms of a particular element have the SAME number of protons (All Carbon atoms have 6 protons)
In a neutral atom, the atomic number = the number of electrons
What is a neutral atom?
Neutral atoms have no overall charge
# of Protons = # of Electrons
How Many Electrons?
Copper (Cu) has an atomic number of 29.
How many electrons does it have?
Also called atomic weight or Mass Number
Sum weight of protons and neutrons in an atom
Periodic Table Atomic Number Element Symbol Mass Number 29 Cu 63.546
Mass number = protons + neutrons
Neutrons = mass number – protons
How many neutrons does Copper have? 35 Mass # = 63.546 (rounds to 64) Neutrons = 64-29 =
Atoms of the same element with different numbers of neutrons.
Isotopes Carbon 12 Carbon 13 Carbon 14
Negatively charged sub-atomic particle
Weight = 0.0006 atomic mass unit
Form an electron cloud (area where electrons are likely to be)
# of protons does not equal # of electrons
Positive Ion --- cation
More protons than electrons
Negative Ion --- anion
More electrons than protons
Number of elements
Oddly enough, the exact number of naturally-occurring elements is uncertain. Uranium (atomic number=92) is the element with the highest atomic number found in significant quantities on earth or elsewhere . The elements astatine (atomic number=85) and francium (atomic number=87), along with all the other known elements (up to atomic number 109) were discovered when first made artificially; if they occur naturally, then they exist only in exceedingly small amounts.
Discovering the Elements. United Learning (1996). Retrieved October 12, 2006, from unitedstreaming: http://www.unitedstreaming.com/
Physical Science Series: Atomic Structure and the Periodic Table. United Learning (1998). Retrieved October 12, 2006, from unitedstreaming: http://www.unitedstreaming.com/