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Properties of AtomsChapter 3

Write the notes that are colored RED!

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History of the AtomGreek Philosopher Democritus, more than

2,300 years ago, proposed that matter is composed of small particles.

John Dalton in 1850 theorized that all atoms of an element contain the same type of atom.

Ernest Rutherford proposed the name ‘proton’ for the positively charged particles in the nucleus of an atom after WWI (in 1911)

Neils Bohr in 1913 proposed that electrons travel only in certain successively larger orbits. He suggested that the outer orbits could hold more electrons than the inner ones, and that these outer orbits determine the atom's chemical properties.

The Elements

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Properties of Matter

If you break a piece of matter in half, and then break it in half again, how many breaks will you have to make before you can break it no further?

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The Building Blocks of Matter Matter: Anything that takes up

space Atom: tiny building blocks of

matter, made up of protons, neutrons, and electrons

Elements: substances that are made up of only one type of atom

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What makes up an Atom? Protons: particles that

have a positive (+) charge Neutrons: particles that

have no electric charge Electrons: particles that

have a negative (-) charge

An atom is mostly

empty space!

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The term electron cloud is used to describe the area around an atomic nucleus where an electron will probably be. It is also described as the “fuzzy” orbit of an electron.

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How many protons and neutrons ?

Atomic Number = the # of protons (+) in the element.Ex: all Iron atoms contain 26

protons Atomic Mass = the # of

protons (+) plus the # of neutrons.

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How many electrons? Neutral atom: the number of protons is

equal to the number of electrons8 p+ = 8 e-

Positive charge: the number of protons is greater than the number of electrons8 p+ > 6 e-

Negative charge: the number of protons is less than the number of electrons8 p+ < 10 e-

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Isotopes Isotopes: Atoms of the same element

that have different numbers of neutrons. Medical doctors use radioactive isotopes to

treat certain types of cancer; geologists use isotopes to determine the ages of some rocks and fossils.

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Introduction to the Elements:

Element Song

By:

Tom Leher

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Looking at the Periodic Tabletext page 106

Elements are arranged according to increasing atomic number

Elements are separated into columns (called groups) and rows (called periods).

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Electron Orbital All of the elements in a period

have the same # of atomic orbitals. All of the elements in a group have

the same # of electrons in their outer orbital, or shell.

A valence electron is an electron located in the outermost shell (shell) of the atom, that can be transferred to or shared with another atom.

It is very difficult for

anything to penetrate

the electron could & hit

the nucleus.

Drawing atomic models

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Using the rules draw :

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Boron Oxygen

Now in your notebook draw Helium and Lithium

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Homework: Complete the worksheet on drawing atoms. See if you can figure out 19 and 20

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How to draw isotopes

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Now try these

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Stability & Chemical Bonding If matter is stable, it tends not to

bond with other atoms. Ex: salt (outer energy level is full)

If it is unstable, it is more likely to bond with atoms. Ex: copper (outer energy level is

not full)

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Compounds Compounds: Matter that is made of

2 or more elements & has physical and chemical properties different from each of the elements that make it up. Ex: Water is made up of hydrogen

and oxygen (H20) and table salt is sodium chloride (NaCl)

Compounds must be separated by chemical meansEx: drop HCl on CaCO3 and

CO2 is released.

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Bonding

Covalent Bonds:

When atoms share the electrons in the outer portion of their electron cloud

Ionic Bonds:

When one ion gains or loses an electron to another ion, they bond together.

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Mixtures Mixture: 2 or more substances that are

NOT chemically combined Heterogeneous mixture: not mixed evenly

& components retain their own properties Ex: trail mix, rock, beach sand

Homogeneous mixtures: evenly mixed throughout & components do not retain their own properties Ex: Kool-aid, salt water, cake batter

Mixtures can be

separated by

physical meansEx: Let the water evaporate from a saltwater mixture

Balloon Bonding You will show me ionic and covalent bonds using

the balloon as your electron

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How to draw Louis dot structure 1. draw the element 2. Erase middle (leave the outer shell) 3. Replace middle with symbol 4. Only leave the outer shell electrons

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Now lets try some louis dot structures on the white boards

Boron Carbon Sodium Helium Argon Yttrium Tin Polonium Krypton –Why is this one different? The rule of octet

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Ionic Bonds (metal + nonmetal):

Draw Na and Draw Cl

It is easier for Na to loose 1 and Cl to gain 1 so NA would be 1+ and Cl would be 1- because of the amount of positive and negative charges they have

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Covalent Bonds (nonmetals) :

Atoms share electrons No charges How does h2O happen? Try to

draw it

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Balancing Equations In a chemical reaction substances

change into other substances by the breaking of old chemical bonds and the forming of new ones.

To represent chemical reactions we use symbols and formulas called chemical equations.

Law of Conservation of Matter: matter can not be created nor destroyed, only changed from one form to another.

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Balancing Equations cont. Balanced chemical equation has the same #

of atoms of each element on the left side (reactants) of the yield (arrow) as on the right side (product).

Arrow () means “reacts to produce” or “yields”

Substances on the LEFT side are reactants Substances on the RIGHT side are products Subscript: number of atoms present of an

element in a formula Cannot be changed in the equation

Coefficient: places in front of a formula to change the number of atoms of each element

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Balance the following equations: ___F2 + ___S ___SF6

___Zn + ___O2 ___ZnO

___H2 + ___I2 ___HI

___B + ___F2 ___BF3

___N2 + ___H2 ___NH3