Post on 20-Jul-2016
transcript
Learning Targets
I can distinguish between chemical and physical “separation.”
I can distinguish between mixtures, compounds and elements.
I can interpret the information on a periodic table.
I can identify the key elements of life. I can describe the structure of atoms
Classical Elementseverything is made from a unique combination of these
four
WaterFireEarthAirHow could
people have been so foolish?
Physical Means
Doesn’t change the identity of a substance.
Change of state (melting, boiling, etc ...) Breaking Magnetism Dissolving Distillation (separation by boiling points) Chromatography (separation by mass)
Mixtures, compounds, elements
Mixture: substances joined together by physical means.
Compounds: elements joined together by chemical means.
Elements: substances that cannot be separated by physical or chemical means.
Air
Air: mixture of N2, O2, CO2
Water molecules also present (humidity)Air components can be separated by melting
point differences.
Earth
Earth is a mixture of salts, metals, organic matter, air, and water.
Can be separated by different physical means.
Water
Pure water is a compound of hydrogen and oxygen.
Volume: 66.6% H, and 33.3% OMass: 11.1 % H, and 88.9% O
Fire
Fire is light and heat, just energy not matter.Only exists from the result of a chemical
reaction.
What are elements?
Things that cannot be separated by physical or chemical means.
The same elements share the same physical and chemical properties.
There are currently 118 (discovered / created) elements, 98 of them found naturally on earth.
How do elements differ?
Matter is mass and volume, so different elements must have different mass and volume.
Density = mass / volumeDensity of elements was first used to
differentiate the elementsNowadays they differ by atomic number
(number of protons)
Periodic Table
Attempt to classify and organize elements.First designed by Mendeleev, based on the
element’s mass and properties.The periodic design allows the prediction of
properties of unknown elements.http://www.youtube.com/watch?v=nsbXp64YP
RQhttp://www.ptable.com/
Types of elements
Metals: Left side of “stairs”
Metalloids: touching the “stairs”
Non-metals: right side of “stairs” plus Hydrogen
Groups and Periods
Periods are the horizontal lines, there are 7 periods currently on the periodic table.
Groups are the vertical lines, elements on the same group generally have similar properties.
Groups Lithium
Sodium
Potassium
Rubidium
http://www.youtube.com/watch?v=uixxJtJPVXk
Main Groups
Alkali metals: Li, Na, K (1)Alkaline earth metals: Be, Mg, Ca (2)Transition Metals: Fe, Cu, Ni, Zn, Ag, Au, Hg
(middle section)Halogens: F, Cl, Br, I (17)Noble Gases: He, Ne, Ar, Kr, Xe (18)
What do elements look like?
Democritus (Greek philosopher) was first to come with the idea of atoms.
Dalton (English chemist) revived his idea 2 thousand years later.
Subatomic Particles
Nucleus: proton and neutronsOuter portion: electronsProton: positive, 1 amu (atomic mass unit)Neutron: neutral, 1 amuElectron: negative, 0.0005 amu
Subatomic particles
Atomic number = # protons
Atomic mass = # protons + # neutrons
# protons = # electrons
Electron Configuration
Electrons are attracted to the nucleus, but they repel one another.
Electrons arrange around the nucleus at different locations, called configurations
These locations are called orbitals, shells, or energy levels.
Valence electrons
The electrons on the outermost energy level.The valence electrons are the ones involved
in chemical reactions.
Isotopes
The number of protons define the element.
The number of neutrons make the same element heavier or lighter.
Isotopes are atoms of the same elements with different masses, different number of neutrons.
Building atoms
http://www.teachersdomain.org/assets/wgbh/nvhe/nvhe_int_elements/index.html