Elements and AtomsBuilding blocks of matter

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)

Chemical Means

Changes the identity of a substance.

BurningElectrifyingChemical reactionLight

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)

Life ElementsCHONPS – Carbon,

Hydrogen, Oxygen, Nitrogen, Phosphorous, and Sulfur

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.

Electron configuration

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.

Isotopes

Building atoms

http://www.teachersdomain.org/assets/wgbh/nvhe/nvhe_int_elements/index.html

Recap

What were the classical elements? Why are they not considered elements anymore?

How do we define an element?How is the periodic table organized?What are valence electrons?