Atoms• Atom – smallest particle of an element that retains the characteristics of that element.

• Element – the most simple chemical substance

• Arranged in the periodic table– Columns and rows– Each element is

identified via 1 letter or 2 letter abbreviation

Structure of an Atom

• Composed of a Nucleus

– Contains Protons (p+)

– Contains Neutrons (n0)

– Protons + Neutrons = Atomic Mass

– # protons = atomic number

• Surrounded by Electrons (smaller particles) with negative (e-) charges.

– Travel in regions called energy levels

• 2 in 1st shell

• 8 in 2nd shell

• 18 in 3rd shell

Crash course on the Periodic Table• Columns go up and down• Rows go left and right• Metals are left of the zigzag, Nonmetals

to the right (except H)• Elements are uncharged, which means

the number of protons MUST EQUAL the number of electrons

• Column numbers tell you valence shell electron number (I.e. their bonding pattern)

• Valence shell electrons are the outermost electrons on an atom.– Hydrogen 1, 1 valence e-– Oxygen 16, 6 valence e-– Carbon 14, 4 valence e-– Nitrogen 15, 5 valence e-

What element am I? _____________________atom

am I?

Bonding - Ionic

• Elements become “happy” when they have a full valence electron shell– 2, 8, 18, etc

• With elements only 1 or 2 electrons away from a full shell will lose or gain electrons.

• Bonds between metals and nonmetals.

• The charge between the elements keeps them attracted together (ions)

• Compound – atoms held together by ionic bonds.

Common Bonds in Biology• Covalent Bonds are the most common in

Biology.

• Organic in biology means “made of Carbon.”

• Isotopes – atoms of the same element that contain different numbers of neutrons.

Bonding - Covalent• When elements have about

4 electrons to gain or lose, they elect to share electrons!– Saves energy, easier to do

than to steal!

• Occurs between nonmetals.

• Water uses covalent bonds.

• Molecule – atoms held together by covalent bonds.

Properties of Water• Consists of 1 Oxygen atom and

2 Hydrogen atoms per 1 water molecule.

• Water resists temperature change (insulator)

• Has three phases:– Solid (ice), liquid, gas (vapor)

• Carries substances via Osmosis.– Serves as material transportation– Blood, plant sap

• Water makes up 70-95% of organisms.

• Cycles through the kidneys and eliminated out of the body

Hydrogen Bonds• Water – a polar molecule

– Means it has a slightly positive (+) end and a slightly negative (-) end.

• Because of its polarity…• Bonds to other water molecules

through Hydrogen Bonds - Holds large molecules like

proteins together• Sticks together (+ and – attract)

to create a cohesion via surface tension

• Good solvent• Can adhere creep up tubes via

capillary action.- From ground to tops of trees.- The meniscus in a graduated cylinder

Mixtures• A mixture is a combination of

substances where both substances keep their original properties.– Physically mixed, not chemically

mixed.• Solution – one or more substances

(solutes) are distributed evenly in another substance (solvent) (water)– The more solute in a solvent,

the higher the concentration.– Organisms need to maintain a

certain concentration for life processes, called homeostasis.

• Suspensions – mixtures of water and non dissolved particles– Example: Blood

pH Scale• pH – a measure of how acidic or

basic something is.• Use pH paper to test• Acidic range is 0-6

– Acids form H+ ions in water– Example: Lemon (2)

• Neutral is 7– Example: Pure water and blood (7)

• Basic range 8-14– Bases form OH- ions in water– Example: Ammonia (12)

• Buffers – weak acids and weak bases that react with strong acids or bases to prevent sudden changes in pH.

• Neutralization reaction:– HCl + NaOH → HOH + NaCl