What is an atom? An element? A molecule? A compound?
Atom: Each element is composed of identical particles called atoms
Element: All matter is composed of chemical elements. Elements cannot be chemically broken down into simpler substances
Molecule: Two or more atoms can stick together to form a molecule
Compound: A substance consisting of two or more elements combined in a fixed ratio.
Which six elements make up roughly 99% of human body mass?
i. Carbon (C)
ii. Nitrogen (N)
iii. Oxygen (O)
iv. Hydrogen (H)
v. Calcium (Ca)
vi. Phosphorus (P)
What are the three subatomic particles? Their charges? Which subatomic particle is
responsible for defining the element? Which is responsible for its reactivity?
1) Protons → found in the nucleus and have a positive charge (p+). Also atomic number
2) Neutrons → found in the nucleus and have no charge (n0).
3) Electrons → travel around the nucleus in orbitals (shells) and have a
negative charge (e-).
- each shell holds a specific # of
electrons.
- outermost shell = valence (responsible for reactivity)
What is the atomic number? Atomic mass/weight? What is an isotope?
Atomic number (# of protons)
Mass number (protons + neutrons)
Isotopes are atoms of elements that differ in the number of neutrons.
How many electrons fit into a single orbital? How about the first shell and second shell? What
do we call electrons in the outer shell that dictate how the atom reacts?
1st shell has 2 e- (nearest to nucleus)
2nd shell has 8 e-
3rd shell holds 8 or more e- (max 18 e-) these are valence electrons.
What is a stable number of electrons in a valence shell? What are the three basic types of chemical bonds? What is a double bond?
stable number for most elements is 8 electrons
* Chemical bonds are formed to achieve complete shells of electrons= chemical stability.
* The two strongest chemical bonds are ionic bonds and covalent bonds, hydrogen bonds.
double bond: two atoms share two pairs of electrons, for a total of four bonding electrons.
What is electronegativity?
a measure of an atom’s attraction to shared electrons.
What are polar bonds and why is this important for water?
electrons not shared equally
between atoms.
every one oxygen atom will need two hydrogen atoms to form water.
What is a hydrogen bond?
formed when a hydrogen atom with a partial positive charge attracts the partial negative charge of a nearby
electronegative atom (most often
N or O)
What are some of the unique properties of water because of this hydrogen bonding?
most abundant and important
inorganic compound in all living organisms
- high freezing & boiling
points - high heat capacity.
- high heat of vaporization.
- it’s a universal solvent.
- cohesion & adhesion.
- high tensile strength.
- quirky properties of density
What is a solution? A solvent? A solute?
- A solution is a liquid consisting of a
uniform mixture of two or more
substances. - The agent being dissolved is the solute.
- The liquid that functions as the dissolving agent is the solvent
What is the hydrogen ion concentration and pH of pure water?
1 pH unit = a 10X
change in H+ concentration
pure water = 7 or 10
Know how the pH scale works
Acid = value less than 7; base = value higher than 7. pH is a measure of the hydrogen
ion concentration. The higher the hydrogen ion concentration, the more acidic a substance is,
which means the lower its pH value.
What is a buffer?
substances that minimize pH
change by accepting H+ ions when they’re in
excess or donating H+ ions when they’re
depleted.
e.g. of this is the pH of human
blood, which has a pH maintained between
7.35-7.45
What causes acid rain? What are some of the effects of acid rain?
When we burn fossil fuels, they release gases that can
react with water to form sulphuric and nitric acids
damaging ecosystems by acidifying water and harming aquatic life, stripping essential nutrients from soil, and weakening trees by damaging leaves = making them more vulnerable to pests and disease
What causes ocean acidification? What happens to the pH of the oceans as they become
more acidic (or less basic)? How does this affect the shells of many sea creatures, including
most with shells and things like corals?
Ocean acidification hinders the
ability of coral animals to build
their calcium carbonate
structures we call coral reefs.
Ocean pH decreases
Ocean absorbs excess CO2 from atmosphere which created carbonic acid.
