Chapter 7 Flashcards
what is Zeff?
effective nuclear charge
what is the formula for Zeff?
Zeff = Z - P
Z = atomic number P = # of core electrons
e. g. Zeff(Al) = 13 - 10 = 3
e. g. Zeff(Si) 14 - 10 = 4
what is the trend for Zeff?
increases to the right
decreases going down a group
what is the trend for atom size?
size increases down a group
generallyy decreases from left to right
explain the trend for atom size
group: b/c same outer shell electron configuration and increase in n (orbital size)
family: b/c Zeff increases and inner electrons shield outer electrons from the full positive charge of the nucleus
which is bigger, cation or anion?
anions are bigger in atomic radius, cations are smaller in atomic radius
how do you determine size for ions?
if they all have the same number of electrons, the atom with the most protons has the highest Zeff —> the higher the Zeff the smaller the radius
how do ions move in an electronic device?
from cathode to anode when charging
when using electronics they discharge from anode to cathode
what is the first ionization energy?
the energy required to remove the highest energy electron from neutral gaseous atoms
the energy is POSITIVE
second ionization energy
second ionization energy: I2: always requires more energy than I1 because removing a negative particle from a positive ion
IE trend
IE decreases down a group because: atomic radii increases down a group and +/- attraction decreases with greater distance: electrons are further away from the nucleus and aren’t as tightly bound
IE generallyyyy increase across a period from left to right because electrons are held tightly: Zeff is greater
exceptions to the IE trend?
elements with filled s or half filled p subshells have higher IE than expected
- Be > B: Be is 2s and B is 2p. electrons in 2p are shielded from the positive charge of the nucleus by electrons in the 2s orbital. electron in the 2s orbital are not effective in shielding each other
- N > O
- Zn, Cd, Hg
what is electron affinity?
the energy given off when adding an electron to a gaseous atom
- not a well established trend
- second EA always requires energy (endothermic) b/c a second electron must be forced onto an already negatively charged ion
metallic character trend
metallic character increase from right to left and top to bottom
why do metals form cations?
low IE
why do nonmetals usually form anions?
high IE and EA
nonmetals
form molecules
metals
form ionic compounds
oxides of metals
basic
oxides of nonmetals
acidic
metalloids
IE are too high to form cations
EA too negative to form anions
group 1A
- alkali metals
- soft
- low density
- form M+ ions
what are the most important alkali metals?
Li, K, Na
- occur in oceans, salt beds, and minerals
- preparation of free metals by reduction:
LiCl —> 2Li(s) + Cl2(g)
what happens when alkali metals react with oxygen?
- react with oxygen: most be stored in oil because they redly react with the air
- oxides form with Li
- peroxides form with Na
- superoxides form with K, Rb, and Cs
what happens when alkali metals react with water?
Li: moderate
Na: rapid
K: in flames
Rb and Cs: explode
group 2A
- alkali earth metals
- harder
- more dense
- less reactive than Group 1A due to smaller size and increase in Zeff
- form M+2 ions
what are the most important alkali earth metals?
Mg, Ca (most abundant too)
- occur as silicates, carbonates, and sulfates
- magnesium is even found in the ocean
what happens when alkali earth metals react with oxygen and water?
react less vigorously with oxygen and water than 1A
CaCO3(s) + heat -> CaO(s) + CO2(g)
CaO(s) + H2O(l) + Ca+2(aq) + 2OH-(aq)
Mg+2(aq) + 2OH-(aq) —> Mg(OH)2(s)
Mg(OH)2 + 2HCl(aq) —> MgCL2(s) + 2H2O(l)
hydrogen
- diatomic (H2)
- odorless, colorless gas
- 3 isotopes
- 1s1: high IE so shares e- in covalent bonds like H2O
- can also gain an electron (ionic bond like in NaH)
what are the isotopes of hydrogen?
1H: hydrogen: 99.9%
2H: deuterium: .01%
3H: tritium: radioactive
oxygen
- diatomic (O2)
- odorless, colorless gas
- 21% air composed of oxygen - isolated from air
- has allotropes
- has 3 ions
what are allotropes? what are oxygens allotropes?
same element but different compounds
O2 and O3(ozone)
3O2(g) + 284.6kJ —> 2O3(g) + O2(g)
what are the 3 ions of oxygen?
- oxide (O^-2): C/S/P vs Li/Ca/Al
C: CO vs. CO2
P: P2O10 vs. P4O6(acidic)
S: so2 vs SO3
- peroxide(O2^-2): unstable
2H2O(aq) —> 2H2O(l) + O2(g) + 196.1 kJ
- superoxide (O2^-1): rescue maskssulfur
S8
- a ring
- yellow solid
- makes acidic solution
- S^-2(sulfide): S(s) + O2(g) —> SO2(g) —> SO3(g)
nitrogen
- diatomic (N2)
- odorless, colorless gas
- 78% of the air - isolated from the air
what is the range of charge for the ions of nitrogen?
-3 to +5
find oxidation state of nitrogen
N2O5
NH3, N2H4
N2O, NO, NO2, N2O4, HNO2, HNO3
phosphorous
P4
- strained Td solid
- formed with: rock + sand + coke:
Ca3(PO4)2 + SiO2 + C —> CaSiO3 + CO + P
- 3 allotropeswhat are the allotropes of phosphorous?
white, red, black
halogens
- high EA….X-
- you always make an acid when you combine a nonmetal with water: Cl2(g) + H2O(l) —> 2HCl(g)
nobel gases
- monoatomic
- full s and p shells
- high IE
- thought to be unreactive until 1962: XeF2, XeF4, XeF6
why does IE of nobel gases decrease as you move down a group?
decreases as you move down b/c IE is taking an electron away and the atom gets bigger as you go down so it’s easier to take an electron
carbon
- solid
- covalent bonding
- CO, CO2, H2CO3 (buffer in our blood)
- hydrocarbons
- 2 forms
what are the 2 forms of carbon?
crystalline and amorphous forms
silicon
- solid
- prepared with sand and coke
- semiconductors that power our devices
- SiO2
- silicates: SiO4^-2 (asbestos)
- silicones - (SiOR2)n - caulk, implants
SiO2
sand and window glass
boron
- octet exception
- rocket fuel
- B2H6 + O2 —> B2O3 + H2O + 2030kJ (HC Brown 1979 Nobel Prize)
among the nonmetallic elements, the change in atomic radius in moving one place left or right in a row is smaller than the change in moving up or down. explain.
when moving up or down you add an entire shell because n increases. when you move left or right only zeff varies which played a minor roll in comparison
explain any difference in the orders of atomic and ionic size when it comes to anions and cations of atoms
anions are larger than cations. secondly, these ions are isoelectronic so when looking at size, the atom w/ the highest atomic # and most protons is the smallest because Zeff is larger
Na2O + H2O –>
NaOH
BaO + H2O –>
Ba(OH)2
N2O5 + H2O –>
HNO3
SO3 + H2O–>
H2SO4
HNO3 + Sc2O3 –>
Sc(NO3)3 + H2O
what is needed to make a basic solution?
H2O
in born haber, make sure to double BOTH Hf and IE/EA if needed (like in MgCl2)
DONT FORGET
what do you always make when you combine a nonmetal with water?
an acid
Cl + H2O –> HCl
