Chemistry Intro• ancient thinkers said there must be a smallest part

that stuff is made up of, this was called the atom

• scientists discovered that atoms are actually made up of smaller particles

• Proton:• Neutron:• Electron:

Linked

• atoms have equal number of electrons and

protons so there are overall charge is zero• electrons stay around nucleus because of

positive/negative attraction with protons• most of the atom is empty space where

electrons move

LinKed

• e- are found in energy levels (specific distance from nucleus) & sublevels (orbital or movement shape/pattern)

• e- move in complicated patterns determined by attractive force of nucleus

• to be stable (“happy”) ALL atoms want 8 e- in their outer most (valence) energy level

Element - pure substance that cannot be broken down into simpler substances

Practice:

Periodic Table of Element• Horizontal rows gives # of energy level of electrons• Blocks give sublevel (electron orbital shapes)

Linked

valence – outer most energy level

Isotopes• Most elements are uniform mixtures of 2 or more unique

substances called isotopes.• Isotopes of an element have very similar chemical

properties but their atoms have slightly different massesWhat about the different atoms, of the same element, could make their masses different??? _________________

____________________________________________________________________________________________________

Linked

BrainPOP

Compound is a pure substance that

• is made from 2 or more different elements chemically combined

• are always formed from a specific combination of elements in a fixed ratio

• cannot be broken down into simpler compounds or elements by physical means.

• Atoms are identified by their elemental symbol within a formula

• Subscripts tell how many atoms of that element are present in the compound/molecule

i.e.) “urea” - CO(NH2)2 [from Wikipedia ”Urea serves an

important role in the metabolism of nitrogen-containing compounds by

animals and is the main nitrogen-containing substance in the urine of

mammals”]

C: 1O: 1N: 2H: 4

Molecules & Chemical Formulas

PracticeHow many atoms of each element are there in each formula?

KHCO3 H2SO4

(NH4)2SO4 (CH3)3COH

What keeps atom together to make compounds?

All atoms want a full valence shell (8)

• Atoms with less than 4 valence will give electrons away to make 8

• Atoms with more than 4 valence will take electrons from others to make 8

• ion – atom got charged so it could get 8 valence

• cation – positive charge• anion – negative charge

Ionic Bonding • Oppositely charged ions attract (the attraction

“glues” the ions together) and is called “ionic bond”

Examples

Mg N

Al O

What happens when neither atoms wants to give valence electrons? How can each get 8???_______________________________________________

– shared e- “belongs” to both atoms– both valences are full– valence energy levels of overlap

• the sharing/overlap binds the atoms together and is called a covalent bond

Linked

Examples

CHCH4

C2H2

What about water? Formula for water ______

Water is called the universal solvent (“can dissolve a lot of stuff”)

Why can water dissolve so much stuff???

ion–dipole attraction separates NaCl formula units into isolated ions

dipole-dipole attraction cause water molecules to surround and isolate sugar molecules

When sharing, why would one interacting thing get more than another??? ____________________________________________________________________________________________________

Molecular (“Pull”) Polarity• Stronger atom PULLS electrons toward its-self• Creates area with more electrons (negative charge)• Thus, the molecule becomes partially charged • Has an area that is a little negative and another area

that is a little positive

water is polar (“puller”)

Polarity results in ….Intermolecular (Van der Waals)

ForcesDipole-Dipole - of one molecule attracts to the of another

Hydrogen bondingdipole-dipole attraction of H in a polar bond to an F, O, or N in another molecule

H bonding is stronger than regular dipole-dipole due to an unshared electron pair

Linked

Van der Waals forces of water(linked)

cohesion (molecules sticking together) causes water to form drops that are nearly spherical, and adhesion ( molecules sticking to another substance) keeps the drops in placeCapillary action – ability of water to flow up a thin tube without assistance against gravity

Mixture -combination of two or more substances (called components) each retaining its individual identity and properties

• Heterogeneous– mixture that looks different & is different• Homogeneous – mixture that looks the same

BUT is different

–solution – evenly distributed homogeneous mixture

– Solute – part that “does the dissolving”– Solvent – part that gets “dissolved”

M&M’s “look” different (linked)

Coffee with cream & sugar looks the same

sugar -

water -

Changes in Matter • Physical change – alters a substance without

changing its composition• may result in drastically different appearance BUT composition of substance remains unchanged– Examples:

H2O H2O H2O

Acids & Bases

• Acid – substance that releases H+ in water

• Base – substance that releases OH- in water

H+ + O H- • strength of acid/base measured by pH = -

log [H+]• the more H+ the more acidic BUT the

lower the pHlinked

Changes in Matter

• What is a chemical change?– matter is neither created nor destroyed– new substance(s) are made from rearrangement

of atoms

• How do you know new substances have been made?– will have new physical properties

• Chemical change (“reaction”)– a process that involves one or more substance changing into new substances

• substances formed after change have different compositions & properties from those present before– Examples:

Changes in Matter

Linked

Writing Chemical equations• We use formulas and symbols to describe

a chemical rxn

• If substance A is mixed with substance B and the two undergo a chemical change that produces substances C and D we write:

A + B C + D

A and B are called the reactants (left side of arrow)

C and D are called the products (right side of arrow)

Balanced Chemical Equations

• Glucose and oxygen react to produce carbon dioxide and water

C6H12O6 + O2 CO2 + H2O

coefficient – BIG number written in front of reactant/product• tells you # of molecules

What about the law of

conservation of matter???

tells you # of atoms