Basic Chemistry

Atoms, Elements and How They Behave

In this Universe…..

There is…….

•Matter – anything that has MASS and takes up space.

•Space – what is not matter.

•Which is there more of????

Where did matter come from?

Big Bang

• Approx. 13 BYA• Produced enormous amounts of energy!• Energy eventually “chilled” enough to form basic building blocks of matter

• Evidence???• Expanding Universe

• Red-shift

• Background radiation

Building an atomAtoms = basic unit of matter

Made of…

•Electrons (e-)• small, no mass, negatively charged

•Protons (p+)• Has mass, positively charged

•Neutrons (n0)

• Has mass, no (neutral) charge

Atom structureProtons and Neutrons are located near the center of the atom and form the NUCLEUS

Electrons orbit around the nucleus in specific electron orbitals/shells.

Why are electrons attracted to the nucleus?

What keeps the electrons from “crashing in?”

KEY POINT!!!!Atoms, can have DIFFERENT combinations of electrons, neutrons and protons!

These different combinations makes the atoms BEHAVE differently and have different properties.

Introducing the elements!

So where did all these different atoms come from????Telling the story of matter….

-Big Bang HUGE amount of energy released

-Energy “chills” and starts to form basic building blocks of matter

-First atoms form Hydrogen and Helium.

-Hydrogen attracted to other hydrogen Big balls of hydrogen

-FUSION REACTION (aka starts) smaller atoms fuse together to form heavier elements (carbon, nitrogen, phosphorus sulfur).

-SUPER FUSION In supernovas even heavier elements are formed.

Where this leaves US!

Approx 5 BYA…

-some leftover space debris from star cycles start to coalesce in different ways

-Hydrogen collected in center starts a fusion reaction = our sun ignites

-Circling debris coalesces to form planets

What we have on Earth

Atoms can exist in varying forms on earth

-Compounds

- Two or more different atoms bonded together

- Ex. H20, CH4

-Elements

- substances consisting of only one type of atom.

- A single atom is the smallest amount of an element you can have.

- Ex. O2, H2

Structure of an Atom

P+

P+

N

N

e-

Nucleus

Orbit

e-

Structure of an Atom

PP

N

N

e

e

Nucleus

Orbit

e

ee

e

e

e

e

e

e

Each Orbit is a specific

distance from the nucleus.

P

P

N

N

e

e

Structure of an Atom

Distance increases as energy level increases.

PP

N

N

e

e

Structure of an Atom

Atomic Theories and Discoveries

Dalton: Late 19th century

- thought the atom was nothing more than a tiny indivisible sphere

Rutherford’s view of the atom

Nucleus contains protons and neutrons

Number of protons dictates which element.

Electrons circle nucleus in orbits.

Bohr’s view of the atom

Electron orbits exist at only certain energy levels (distances) from the nucleus.

Bohr’s view of the atom

Each orbit holds only a certain number of electrons

Orbit 1 – max 2Orbit 2 and 3 – max 8

Bohr’s view of the atom

Valence Electrons: Electrons in the outermost orbit; - determine which atoms can form bonds together

Bohr’s view of the atom

Elements with full “outer shells” do not react

Noble or “Inert” gases: He, Ne, Xe

The Periodic Chart

Atomic number = number of protons

Atomic Mass is the “approximate” number of protons + neutrons

If atom has a charge of zero, Electrons = Protons

Ions

atoms with a positive or negative charge

created by adding or losing electrons

•How do we get a + ion??

Isotopes

atoms with the same number of protons and electrons but different neutrons

                        

 

                                  

  

CompoundsTwo or more atoms bonded together in a set proportion

MoleculeSingle unit of a compoundContains more than one atom,

BUT can be the same type of atom (O2, N2)

CompoundsStrength of bonds depends on length, angle and Type of bond

•Ionic-•Covalent-

Bonding Animations

Types of Bonds

Ionic: one atom gives electrons to another, creates opposite charges

Types of Bonds

Covalent: atoms share electrons

Bonding – depends on valence e-’s

An atom with < 8 valence e-’s can bond with other atom(s) to fill up the outer shell (reach 8)

Examples:

Na (1Ve) bonds with Cl (7Ve’s)

C (4Ve) bonds with 4H (1 Ve each)

O (6 Ve) bonds with 2H (1 Ve each)

Types of Bonds

Which do you think is stronger?

•Ionic: two atoms attracted by opposite charges?

OR

•Covalent: two atoms holding on to same electrons

Mixtures vs. Compounds

Mixtures have “ingredients” that do not bind chemically with each other

•Each substance keeps its own property

•No definite proportions•Types: solution, suspension, colloid

Chemical Formulas

A chemical formula tells us three things:

•What elements are involved

•How many atoms of each you have

•How many molecules you have

Chemical Formulas•Ex: 3C6H12O6 •This means there are 3 molecules of (C6H12O6 which is glucose)

•1 molecule of (C6H12O6) contains 6 Carbon atoms, 12 Hydrogen atoms and 6 Oxygen atoms

•So how many H’s total are represented in this formula?

Mixtures vs. Compounds

Compounds have different properties than any of the elements that make it up

•Parts are Chemically bound•Definite proportions required

Mixtures vs. Compounds

Mixtures have ingredients that do not chemically bind to one another

•Mixture has same properties as ingredients

•No definite proportions needed

Types of Mixtures

Solution – Homogeneous mixture

•equal composition throughout

•2 or more substances; solvent and solute

•Solute is individual ions or molecules

Can you think of an example?

Types of Mixtures

Suspension – heterogeneous

•looks uniform when shaken or stirred;

•Separates upon sitting (no agitation)

Can you think of an example?

Types of Mixtures

Colloid –

•Mixture of very tiny particles of dispersed in another substance;

•Suspended but do not settle out

Can you think of an example?

Properties of WaterMost important Most important inorganic inorganic compoundcompound in living systems in living systems

Nearly all chemical reactions Nearly all chemical reactions occur in wateroccur in water

Properties of Water

Polar covalent Polar covalent

•Share electrons Share electrons but not equally – but not equally – creates slight creates slight (-)charge in the O (-)charge in the O and a slight (+) and a slight (+) charge in the Hcharge in the H’’s s of waterof water

Properties of Water

Polarity of Water movie

Properties of Water

Cohesion

•Water molecules stick to other water molecules

•Creates a high surfacetension

Properties of Water

Universal SolventUniversal Solvent

Polarity of water allows it to Polarity of water allows it to interact with neighboring polar or interact with neighboring polar or ionic molecules ionic molecules

Dissolves or suspends many Dissolves or suspends many substancessubstances

What will not dissolve in water? What will not dissolve in water?

Properties of Water

EXAMPLE NaCl + HEXAMPLE NaCl + H22O O Na Na++ + Cl + Cl-- + +

HH22OO

oxygen attracts sodiumoxygen attracts sodium hydrogen attracts chloridehydrogen attracts chloride sodium & chloride separate as

ionic bonds are broken

Adhesion

•Water molecules stick to other substances with partial charge

Water

GlassTube

Properties of Water

Water has a high specific heat

•Specific heat is the amount of energy needed to raise 1 gram of water 1 degree.

•Water absorbs a lot of energy before its temp goes up•Keeps earth’s temperature stable!

Properties of Water

Concept of pH – see pH scale and worksheet