Lecture 1 Flashcards
Nucleus includes: (2)
- Neutron
- Proton
Electrons (4)
- occupies large space
- occupies in shells
- inner shell has max 2 e-
- outer electrons, aka outermost shells
Why is carbon 12.03?
- because of isotopes
What is isotopes?
same # of electrons, different neutrons
What are isotopes used for?
- imagining, radiocarbon dating
Radiocarbon dating
use to determine the dead, fossils and how long these bones last for
Mass number (He 4 or 2)
- top # (4)
- # of protons + neutrons
atomic number
- number of protons
All life depends on what in the atmosphere?
- carbon dioxide
Archeology
- the study of human activity through the recovery and analysis of material culture
- takes bones and grind them, see how much C14 are in these bones.
If bones have the same amount of C14 as in the atmosphere, what does that mean?
- recent bone
once u die, the exchange of CO2 stops, C14 starts to decay, gets less and less overtime
What causes the formation of chemical bonds?
To link atoms tgt, to form chemical bonds, only electrons are important.
What elements mostly made up our body? (4)
- hydrogen
- carbon
- nitrogen
- oxygen
Periodic table (group)
same amount of e- in the outer most shell, meaning that they are similar chemistry
Rows (period)
all the amount in the same rows are roughly the same size, because of the same # of shells
Three types of bond
- covalent bond
- ionic bond
Covalent bond (3)
- A covalent bond is made of 2 electrons
- These 2 electrons are shared, i.e. one electron comes from each atom
- Atoms can form bonds until their outermost shell is filled
What is so special about central atom?
95% probability of where e- are
What is nonpolar covalent bond?
Electrons are shown to be superimposed
on the bond to indicate that they are
halfway between the two atoms, shared
equally
Polar covalent bonds
Electrons are not shared equally (O is more electronegative than H), so partial charges exist on the O and H atoms Polar = shared unequally, e- spend more time on the oxygen
Trends of electronegativity
The higher the electronegativity, the stronger the attraction
Valence electron
number of unpaired electrons
What is so special about hydrogen bond? (2)
- A meniscus forms where water meets a solid surface,
as a result of two forces. - high surface tension
- in trees, water can rise up to the top because of hydrogen bond, force that push the water up (evaporation) coz of hydrogen bond
- (a) In ice, water molecules form a crystal lattice.
- (b) In liquid water, no
crystal lattice forms. - (c) Liquid water is denser than ice. As a result,
ice floats.
Adhesion: Water
Water molecules that adhere to the glass resist the downward pull of cohesion
Cohesion: Water
Water molecules at the surface experience a net downward pull from hydrogen bonds with water molecules below
