Chapter 4Earth Chemistry

• Be sure to also review atomic particles

• And the periodic table

Chapter 4:1Matter

 

    

    

    

    

    

    

    

  

Objectives

• Compare chemical properties and physical properties of matter

• Describe the basic structure of the atom• Compare atomic number, mass number,

and atomic mass• Define isotope• Describe the arrangement of elements in

the periodic table

What is matter?

• Matter is anything that takes up space and has mass.

• Amount of matter is the mass of an object

• Observable and measurable properties

All M atter has two m ajor d istinguish ing properties .

D ensity C olor

Physical P ropertiesObserved w ithout changing

the com position of the substance

Iron rusting H elium 's unreactiv ity

C hem ical P ropertiescharacteristics that describe how a

substance interacts w ith other substancesto produce different kinds of m atter.

M atter

Element

• A substance that cannot be broken down into a simpler form by ordinary chemical means.

Primary Earth Elements

OxygenSiliconAluminumIronCalciumSodiumPotassiumMagnesiumAll Others

Bohr_s_Model_of_the_Atom

Atom• Is now defined as the smallest particle of an

element that retains the chemical properties of that element. Made of subatomic particles

NucleusProtons –

positive chargeand

Neutrons -neutral charge

Electrons-have a negative charge

Electron Cloud• Electrons do not orbit around the nucleus

like miniature planets… instead they are found in “clouds” or regions of probability around the nucleus. Electrons

Atomic Number• Each kind of atom has its own distinct atomic

number. Only atoms of that element have the same atomic number.

• Atomic number equals number of protons• Uncharged atom – equal number of protons and

electrons, atomic number = number of electrons• For Example GOLDGOLD, has a atomic number of

79. GoldGold has 79 protons in its nucleus. No atoms have an atomic number of 79 except GOLDGOLD atoms.

Exploring_the_Modern_Periodic_Table

Two_Rows_of_Elements_at_Bottom_of_Periodic_Table

Periodic Table of ElementsElements in same column have similar arrangement of electrons

Using_the_Modern_Periodic_Table

Atomic Symbol

66

CCCarbonCarbon

12.01112.011

[He]2s[He]2s222p2p22

Atomic Number

Atomic Name

Atomic Mass

Atomic MassAtomic Mass• The mass number of any atom is the TOTAL

number of protons AND neutrons in the nucleus of an atom.

• For example GOLDGOLD, has a mass number of 197 amu or atomic mass units.

Isotopes

Atoms of the same element (the same number of protons) with different numbers of neutrons.

They have identical atomic numbers but different mass numbers.

ISOTOPES• Different number of neutrons / different masses yields

isotopes of same element with different properties

Average Atomic Mass

• Weighted average of the atomic masses of naturally occurring isotopes of an element

• Average calculated for Periodic Table

electron

neutron

proton

Valence Electrons• Similarities in chemical

properties places elements in periodic table in columns or groups

• Outermost electrons in cloud are Valence

• Atoms’ number of valence electrons generally same for every atom in that group

Metals and Nonmetals• Elements whose atoms

with only 1, 2, or 3 valence electrons lose electrons easily

• Metallic properties and classified as metals

• Elements whose atoms ranging from 4-7 valence electrons more likely to gain electrons

• Classified as nonmetals

Families__Alkali_Metals__Halogens__Noble_Gases_

Section 4.2 Section 4.2 Combinations of AtomsCombinations of Atoms

Section Objectives

• Define compound and molecule.

• Interpret chemical formulas.

• Describe two ways that electrons form chemical bonds between atoms.

• Explain the differences between compounds and mixtures.

Elements_and_Compounds

Compound

• A substance that is made of two or more elements that are joined by chemical bonds.

• The compound’s properties differ from those of the elements that compose it.

Molecule

• The simplest unit of a compound that retains all of the substances chemical properties.

Diatomic Molecule

• Molecules made up of two atoms, which can be the same element.

• N2, F2, Cl2, O2.

Chemical Formulas

• A combination of symbols and numbers that show which elements, and the number of atoms of each element, that make up a molecule of a compound. The numbers here are called subscripts.

How about (NH4)2CO3?

Chemical Equations

• A formula that describes the chemical reaction of elements and compounds to form new compounds.

Equation Structure

• reactants → products

• The arrow means “gives” or “yields”.

• For the picture, the chemical equation is:

2H2 + O2 → 2H2O

Balanced Equations

• The number of atoms of each type must be equal to each other on either side of the arrow.

• You cannot change the chemical formulas.

• We put numbers (called coefficients) in front of the reactants or products to make it balance.

So, Let’s Balance This Puppy!

CaCO3 + HCl → Ca2+ + Cl− + CO2 + H2O

CaCO3 + 2HCl → Ca2+ + 2Cl− + CO2 + H2O

Chemical Bonds

• The forces that hold atoms together in a molecule.

• Produced by the sharing or transferring of electrons from the outermost (valence) electrons of two or more atoms.

Ions• An atom or group of

atoms that carries an electrical charge from either gaining or losing an electron(s), trying to fill the valence shell and “look” like a noble gas.

• Gain = negative charge Loss = positive charge

Ionic Bond

• The attractive force between oppositely charged ions that result from the transfer of electrons.

Ionic Compound• A compound formed through the transfer of electrons.

• MOST are formed by the transfer of electrons from a metal to a non-metal.

• Example: NaCl (table salt)

Covalent Bond

• A bond based on the attraction between atoms that SHARE electrons.

Covalent Compound• A compound formed by the sharing of

electrons by two or more atoms. Each atom “thinks” that it “looks” like a noble gas.

Diatomic Hydrogen

Polar Covalent Bonds• Chemical bonds are rarely PURELY ionic

or covalent, they are usually somewhat “in between”, and the atoms do not share the electrons equally.

Metallic Bonds (Not In The Book)

Metals_and_Non_Metals

Heterogeneous Mixtures

• Where two or more substances are not uniformly distributed.

Granite, mostly a mixtureof orthoclase and quartz.

Homogenous Mixtures

• Means “having the same composition and properties throughout.”

• Also called a solution, in which two or more substances are uniformly dispersed.

• Can be solid, liquid, or gas.

Smog build-up during the day

AlloyAlloy

• A solution composed of two or more metals.

• For example, this 15th century bronze door is made up of a SOLID solution of copper and tin…BRONZE

Assignment • 4.2 Key Terms• Directed Reading