CH 101 Exam material #1 NCSU Ghiladi

law of conservation of mass

mass is neither created nor destroyed in chemical reaction

law of definite proportions

elements of compound are always present in definite proportions by mass

law of multiple proportions

when 2 different compounds are formed from the same 2 elements, the masses of 1 element that combine with a fixed mass of another are fixed in a ratio of small whole numbers

law of combining volumes (Gay-Lussac)

volumes of reacting gases measured at the same temperature and pressure are always in ratio of small whole numbers

avagadro's law

equal volumes of gases at same temperature and pressure contain equal number of molecules

Particle-Wave Duality

most subatomic particles behave as particles and obey the physics of waves

c

velocity of light: 3x10^8 m/sec, wavelength (delta) x frequency (V)

blue/purple

light with short wavelength and large frequency

red/orange

light with long wavelength and small frequency

E

energy: h x V or hc/(delta)

to find a mol of photons

find E first, then multiply it by avagadros number (6.02 x 10^23)

photoelectric effect

the ejected electrons would have a kinetic energy that was dependent on the intensity of light (that was not observed)

n

determines primary indicator of electron's energy

l

(n-1) describes angular dependance

m _l

orientation in space

diamagnetic

not attracted to a magnetic field

paramagnetic

has unpaired electrons, is attracted to magnetic field

aufbau principle

an electron occupies the lowest-energy orbital that can receive it

hund's rule

electrons occupy orbitals of the same energy in a way that makes the number of electrons with the same spin direction as long as possible (bus seat rule)

ion configurations

to form electrons from elements in s and p blocks, remove 1+ electrons from sub shell of highest n; ex: P= [Ne] 3s^2 3p^3, P^3+= [Ne] 3s^2

d block ion configurations

remove s electrons first, then d electrons

periodic trends

-ionization energy: increases left to right, increase bottom to top
- electron affinity: increase left to right, increases bottom to top
-atomic radius: increases right to left, increase top to bottom
-Z (nuclear charge): increases left to right, increases top to bottom
-Z* (effective nuclear charge): increase left to right, increases top to bottom

Z

nuclear charge, directly from atomic number

Z*

Z*=[Z-(# inner electrons)]: effective nuclear charge, positive charge at nuclear that is "felt", increases across period owing to incomplete shielding, ex: 2s on Li "feels" a +1.3 charge because it is "shelled" by the core

atomic radii

increase down a group (more electrons are added to orbitals father from the nucleus), decrease left to right (greater attraction-->held closer-->size decreases--> owing to increase in Z*)

ionice sizes

cations smaller than correlating element because of decrease in electrons= decrease in size; anions bigger than corresponding element because increase in electrons= increase in size

ionization energy

energy required to remove an electron from atom in the gas phase; increase across period because of higher Z*, decrease going down groups because of electrons being added farther from the nucleus

electron affinity

energy involved when an atom gains electrons to from an anion, nonmetals have high affinity because they gain electrons to form anion

electronegativity

x is a measure of the ability of an atom in a molecule to attract electrons to itself (Linus Pauling); increase left to right, bottom to top; Flourine has maximum electronegativity (atoms with the lowest electronegativity is the center atom in most molecules); electrons are being pulled closer, not gaining

as Z* increases across a period

orbital energies drop because of higher Z that occurs left to right; energy of an electron increases (becomes less negative and bound less tightly) because its n quantum number increases; energy of an electron decreases (becomes more negative and more tightly bounded) as effective nuclear charge increases

DeBroglie

the heavier the object, the shorter the wavelength

when changing n

n=1 to anything will absorb more photons of energy than others

E= -hR (Z^2/n^2)

used when questions asks for energy in specific orbital (n) of specific element; ex: energy of electron in n=3 level of He^1+ ion

E= hR(H)Z^2 [(1/n(l)^2)- (1/n(h)^2)]

used when asking for frequency, energy, or wavelength of spectral line with a low n and a high n

r= (Bohr radius)(n^2/2)

used when asked for Bohr radius with n for specific element