Ch2 - The Chemistry of Life Flashcards
What parts make up an atom? Where are they located?
Proton (+) : center of atom
Neutron (=): center of atom
Electron (-): orbit on electron cloud
What is an element?
substance with only 1 atom
What determines the atomic number & atomic mass?
Atomic number – # of protons & neutrons
Atomic mass – proton + neutron
What are isotopes? Ex
An element with a different # of neutrons
ex. Carbon 14
What are radioactive isotopes?
whose nuclei are unstable (bc of change in # of neutrons)
break down at a constant rate - releasing matter/energy as radiation
Uses of radioactive isotopes?
treat cancer
find age of rocks/fossils
kill bacteria
track movement of atoms within living tissue
What is a compound?
substance formed by 2+ different elements that are bonded chemically
What is a molecule?
smallest unit of most compounds
2+ atoms joined chemically (same or different)
What is a mixture? Two types of mixtures?
2+ atoms not joined chemically
Homogenous: blended well together – will not separate
Heterogenous: Not uniform
What determines chemical bonds?
Valence electrons
What are covalent bonds?
Strongest bond - sharing of electrons between 2 atoms
What are ionic bonds?
Transfer of 1+ electrons across atoms
What is an ion? Example? Types of ions?
Atom that has gained/lost an electron
Ex. NaCl
Cation: Positively charged ion
Anion: Negatively charged ion
What is the octet rule?
Atom is most stable with 8 electrons in valence shell
Bond pair vs Lone pair
Bond pair: 2 electrons that have fomed a bond
Lone pair: 2 electrons that are not involved in any bond
What is the van der waals force?
If two polar molecules are brought together so that atoms touching are opposite charges, their slightly positive and negative charges will cause them to attract (in other words, both surfaces have matching shapes)
What is polarity?
Unequal sharing of electrons causing partial positive and negative charges
Ex. Water molecule – O- H+
What is hydrogen bond?
Between 2 water molecules
Oxygen of 1 molecule and Hydrogen of another molecule – due to partial positive/negative charge
List the properties of water
- Cohesion
- Adhesion
- Good solvent
- Acids & bases
- High heat capacity
- High heat of vaporization
What is cohesion? Example
Attraction between molecules of the same substance
Ex. Water striders can walk on water
Ex. Drinking from a straw
What causes high surface tension?
In water - cohesion causes high surface tension since the bonds are very strong
Explain why water striders can walk on water
Why does ice float?
Ice is less dense than water – hydrogen bonds spread apart in order to be more stable
What is adhesion?
Bonding between unlike molecules
- can counter force of gravity