Ch 2 - Periodic Table Flashcards
How are valence electrons represented on the periodic table?
Roman number above each column
What are A elements?
“Representative elements”
IA to ViiiA
The valence electrons of these groups are in the s or p shells
What are B elements
“Nonrepresentative elements”
Includes transitional elements
(Valence in shells s and d)
And lanthanide and actinide series (valence in s and f subshells)
METALS
Gen info
+ 2 properties
+ 3 atomic properties
Left and centre of periodic table
(Active metals: s subshell)
(Transition metals: d subshell)
Gen high density and high melting points
Generally lustrous solids except mercury which is liquid at reg temp
Malleable and ductile
High electro-positivity
Low ionization energy
Easily give up electrons
What are transition metals?
Group B elements
Valence electrons in d subshell
Many have 2 or more OXIDATION STATES aka charges when forming bonds with other atoms.
Because the valence electrons readily nice around, this makes them good conductors of heat and electricity.
Where are lanthanide and actinide series elements found?
In the section if the f subshell (bottom of periodic table)
NON METALS
Upper right of periodic table
Brittle in their solid state
High ionization
Electron affinities
Electronegativities
(OPPOSITES of metals)
Don’t give up electrons easily
METALLOIDS
“Semi-metals”
Stairs starting from B
Have some metal and some nonmetal properties
Generally are good semiconductors due to their partial conductivity
What is effective nuclear charge?
Z-eff
A measure of the net positive charge (from the protons) experienced by the outermost electrons
THE PULL OF THE PROTONS AS EXPERIENCED BY THE ELECTRONS
Hence, in one PERIOD, the Z-eff increases as the number of proton/electron increases
Principal quantum number and it’s relation to the periodic table:
As we go down a GROUP, the principal quantum number increases
(Hence the other shells if electrons are creating more and more of a reduction in the pull from the proton)
Which group are the noble gases?
Group 18 - far right
Periods versus groups
Periods - rows
Groups /families - columns
Each item on a row has 1 more proton and 1 more electron that the element before it
Each item in a group has similar electronic configuration in the valence shell and share similar chemical properties
Atomic radius
Half the distance between the centre if two atoms of an element that are briefly in contact with each other
OPPOSITE of all other trends: decreases across periodic table from L to R
What is Z-eff?
The effective nuclear charge: the PULL ON THE ELECTRONS
Increases across a period (left to right)
What is ionic radius?
Related to how many electrons the metals/NM/MO’s are going to gain or lose to make an octet, and how that electron charge/pull related to that of the nucleus
Metals near the METALLOIDS line have MORE electrons to give up, compared to strong nucleus pull so the ionic radius is smaller.
Nonmetals near the METALLOIDS line need more electrons to make an octet, hence the ionic radius is larger because they gain electrons while the nucleus stays the same
What is ionization potential / ionization energy?
The energy needed to remove an electron from a gaseous species
Requires input of heat = endothermic process (heat is taken in)
Higher Z-eff - higher ionization energy needed
What are “active metals”?
Metals that give up their electrons very easily (have very low Z-eff hence need low ionization energy)
DONT EXIST IN THEIR NEUTRAL FORMS - always in an ionic compound
ie lithium, beryllium
First ionization and second ionization energies
The energies requires to remove he first electron, the second, and so on.
The second ionization is greater since the electron is being removed from an increasingly cationic (positive) species
Second ionization in Group 1 monivalent cations is especially very high because after the first electron is removed, it has a stable octet configuration!
Electron affinity : is it endothermic or exothermic?
EXOTHERMIC
Gives off heat when an electron is gained
Electronegativity - how is it determined?
Determined by the ionization energy
High I.E = high electroneg
Most and least electronegative elements?
Cs - LEAST
Least electronegative
Lowest ionization energy
Least electron affinity
F - MOST
Most electronegative
High ionization energy
Most ectothermic electron affinity
ALKALI METALS
Group 1
1 valence electron
Low Z-eff
Largest atomic radii
Low electronegativity, low ionization energy, low electron affinity
Readily react w Nonmetals, esp Halogens
Harsh reactions with water and air
ALKALINE EARTH METALS
Group 2 - 2 valence electrons
Slightly higher Z-eff than alkalis
Slightly smaller atomic radii than alkalis
ALKALI METALS AND ALKALINE EARTH METALS are active metals
(Very reactive, bit usually found in their neutral state)
CHALCOGENS
Group VIA - 6 electrons
CRUCIAL FOR BIOLOGICAL FUNCTIONS
Nonmetals and metalloids
Generally have small atomic radii, large ionic radii
Many of these substances in high concentrations can be damaging or toxic
HALOGENS
Group VIIA - 7 electrons
Halogens can be gas, liquid (Br) or solid (I)
Large Z-eff value
Small atomic radii
High electronegativity, high electron affinity,
**rarely found in neutral states: often found as HALIDES, aka ions
NOBLE GASES
Group VIIIA - full octet
“Inert gases” because they have low reactivity
High ionization energy, no or low electron affinity, and usually no measurable electronegativity.
VERY low boiling points - all are gases at room temp
TRANSITION METALS
Role in biology?
B groups (3-12, entire middle)
"Metals" Low electron affinity Low ionizing energy Low electronegativity Large atomic radii
Good conductors, malleable (loosely held electrons)
Very hard, high boiling points
**many of these are cofactors for enzymes
Oxidation states of TRANSITION METALS
They are able to have a varied number of electrons missing, so varied positive charges (or Cu+, Cu2+)
Because of this ability to maintain different positive oxidation states, they can form many different compounds.
Diff oxidation states = diff COLORS
