Ch. 8 Earth Chemistry

Journal: What do we know about matter?

Properties of Matter

• Physical properties: boiling point, melting point, color, luster, density, electrical conductivity, magnetism

• Chemical properties: how a substance will interact with another substance (reactive, unreactive)

Journal: What do we know about

an atom?

Experiments that led to the discovery of subatomic Particles

Rutherford’s Gold foil experiment• Question posed: How will a tiny particle pass

through closely packed atoms?– Took an element: pure gold– Shoot a alpha particle at the gold(helium nucleus:2 protons – 2 neutrons)

• Rutherford’s Hypothesis: If the mass of the atom was distributed evenly throughout the atom, then there would be very little to deflect the alpha particles as they passed through the atom.

• Rutherford’s Result: Most alpha particles went straight through the gold foil but a small amount were deflected at great angles!

Atomic Structure

Atom1. Protons (+ Charge)2. Neutron (Neutral)3. Electrons ( - Charge)

Atomic Structure

Atom1. Protons (+ Charge)2. Neutron (Neutral)3. Electrons ( - Charge)

Nucleus

Atomic Number

• The number of protons in an element• Identifies the element

In an uncharged atom, # protons = # electrons

What is the atomic number of Carbon?

How many protons does carbon have?

How many electrons does carbon have?

What is the atomic number of Carbon? 6How many protons does carbon have? 6

How many electrons does carbon have? 6

Mass number

• Represents the protons and neutrons found in an atom of an element

• Why aren’t electrons included in the mass number?

What defines an atom as one type of element instead of another????

• In other words, what makes one atom a Carbon and the next atom Nitrogen?

• THE NUMBER OF PROTONS!!!

What if the number of protons in an atom stays the same but I add or remove neutrons…..

What would change about that atom?

The Mass Number

Why?? Mass number = protons +

neutrons!

Isotopes

• Elements that have the same number of protons but different number of neutrons

The periodic table organizes atoms with similar chemical properties in columns• The similar properties of atoms in these

groups are due to the number of electrons in their outer most electron orbital

Valence Electrons• The electrons in the outer most electron

orbital

• What pattern do you notice about the number of valence electrons for the elements in each column?

Chemical Bonds

• 2 Main Types(Does any one remember the two types?)

Ionic & Covalent

Chemical Bonds

• Ionic Bonds – electron transfers result in charged atoms called ions– Ions with opposite charges attract forming an

ionic compound

Ionic Bond Example

Predicting typical charges of ions formed

Journal: • How do ions form? When and atoms gains or loses electrons

• How are positive ions formed?Atoms that have lost electrons

• How are negative ions formed? Atoms that have gained electrons

Predicting formulas for ionic compounds

If one ion has a +2 charge, and the other has a -1 charge, how many of each ion would you need for your charges to balance in your final molecule?

+2 -1

Predicting formulas for ionic compounds

If one ion has a +2 charge, and the other has a -1 charge, how many of each ion would you need for your charges to balance in your final molecule?

+2 -1

-1

Predicting formulas for ionic compounds

If one ion has a +2 charge, and the other has a -1 charge, how many of each ion would you need for your charges to balance in your final molecule?

Mg2+ and Cl-

MgCl2

+2 -1

-1

• Covalent Bond - attraction between atoms that share electrons – Occurs between 2 or more nonmetals

Example: Carbon dioxideCO2

Chemical Formulas

• Show the scientist the amount of each element in a particular chemical

Example: Water• Chemical Formula: H2O– There are 2 hydrogen and 1 oxygen in every water

molecule

Mixtures

• Parts keep their individual properties• Can be separated by physical means– Solution: one substance is evenly dispersed in

another• Example: Ocean Water (Water & Salt)

– Alloy: 2 or more metals

The End!

• We learned a lot of information today!

• Journal: What concept was the most difficult for you to understand?