law of octaves john newlands(1865) noticed repeating pattern of properties every eight elements...
TRANSCRIPT
Law of Octaves John Newlands(1865) noticed repeating pattern of properties every
eight elements▪ reminded him of musical scale
never accepted as a law
Dmitri Mendeleev organized the elements by at. weight &
physical and chemical prop. published(Principles of
Chemistry) in 1869▪ one year before Julius Lothar Meyer(although
Meyer started his research about 5 years before Mendeleev)
▪ “I began to look about and write down the elements with their atomic weights and typical properties, analogous elements and like atomic weights on separate cards, and this soon convinced me that the properties of elements are in periodic dependence upon their atomic weights.” --Mendeleev, Principles of Chemistry, 1905, Vol. II
Mendeleev’s periodic law – chemical and physical prop of the elements are a periodic function of an increasing atomic mass
Mendeleev’s table organized by: ▪ atomic mass/weight(columns)▪ properties(rows)
▪ predicted unknownelements/properties▪ eka-aluminum = gallium(68)▪ eka-silicon = germanium(70)▪ eka-boron = scandium(45)▪ possible mistake with Te(128) and I(127)???
Moseley discovers atomic number (1915) periodic law is revised
▪ chemical and physical prop. of the elements are a periodic function of an increasing atomic #
period – horizontal rows
groups/families – vertical columns ▪ similar e- configuration
5.2 e- config and the pd table• main group elements
• s and p block elements
group 2 – Alkaline Earth metals
groups 13 thru 16 no particular names properties vary from metallic to nonmetallic
Halogens – group 17 most reactive nonmetals
▪ react with most metals to form salts▪ halogen(Greek) – salt maker
transition metals – groups 3-12 d-orbital electrons
▪ loosely held by nucleus▪ good elect. conductors▪ very malleable
noble gases(inert gases) – group 18 non-reactive
▪ full outer NRG level▪ stable e- configuration
rare earth elements lanthanide series
▪ shiny metals▪ similar to alkaline earth metals
actinide series▪ unique nuclear structure▪ all are radioactive
hydrogen most abundant element in universe
▪ 75% of all atoms are H 1 p+ and 1 e-
▪ allows for H to bond with many of the elements
5.3 e- configuration and periodic trends
trend – a predictable change in a particular direction▪ typically restricted to main group elements
1) atomic radius half the distance between two bonded
adjacent nuclei
atomic radius trend in a group, as atomic # increases, atomic radii
increases▪ valence e- in higher NRG levels
▪ further from nucleus
▪ more electron shielding▪ e- shielding – blockage of nuclear charge from reaching outer
most e-
▪ another NRG level of e- are shielding outer most e-
in a period, as atomic # increases, atomic radii generally decreases e- in same NRG level e- shielding constant greater nuclear charge
▪ each e- feels greater positive charge pulling▪ outer e- pulled closer to nucleus
2) ionization NRG NRG added to an atom to overcome
attractive forces holding e- around nucleus NRG required to remove e- from atom
A + ion. NRG A+ + e-
Na + ion. NRG Na+ + e-
Br + ion. NRG Br+ + e- creates ions
▪ ion – charged atom
ionization NRG trend
in a group, as atomic # increases, ionization NRG decreases atoms are larger more e- shielding
▪ less nuclear attraction for outermost e- ▪ less NRG required to remove e- Li > Na > K > Rb > Cs > Fr
ionization NRG trend cont.
in a period, as atomic # increases, ionization NRG generally increases atoms are smaller e- shielding constant
▪ greater nuclear attraction▪ more NRG required to remove e- Na < Mg < Al < Si < P < S < Cl < Ar
metals tend to lose e- oxidation – chemical reaction in which a
substance gains a more positive charge by losing e- ▪ originally meant “to form an oxide”
Na = 11p+ & 11e-
Na Na+ + e- = oxidation
Na+ = 11p+ & 10e-
= LEO
3) e- affinity NRG change associated with addition of
an electron to atom▪ positive e- affinity(exothermic)
▪ X + e- X- + NRG▪ most elements▪ Cl + e- Cl- + NRG
▪ negative e- affinity(endothermic)▪ X + e- + NRG X- ▪ few elements alkaline earth metals, noble gases, zn-subgroup full orbitals Ca + e- + NRG Ca-
periodic trend positive e- affinity(only)
▪ in a group, as atomic # increases, NRG released decreases▪ less nuclear attraction for e-
▪ in a period, as atomic # increases, NRG released increases▪ greater nuclear attraction for e-
nonmetals tend to gain e- reduction – chemical reaction in which a
substance gains e- and becomes more negative▪ originally meant “metal ore reduced to metal”
Cl = 17p+ & 17e-
Cl + e- Cl-
Cl- = 17p+ & 18e-
LEO says “GER”
4) ionic radii size of ion after the atom has lost or
gained e- cations – positive ions
▪ created when metals lose e- ▪ Na + NRG Na+ + e-
▪ smaller than their atom▪ size varies with # of e- lost
anions – negative ions▪ created when nonmetals gain e- ▪ Cl + e- Cl- + NRG
▪ larger than their atom▪ size varies with # or e- gained
5) electronegativity attraction an atom has for other atoms e- arbitrary scale
▪ F is most electronegative = 4▪ other elements based on attraction of F
periodic trend▪ in a group, as at. # increases, electronegativity
decreases▪ less attraction due to larger atoms and e- shielding
▪ in a period, as at. # increases, electronegativity increases
▪ greater nuclear attraction
▪ most electronegative = upper right corner – F▪ least electronegative = lower left corner – Fr
6) melting and boiling points melting point - temperature at which solid
changes to liquid boiling point – the temperature(at normal
pressure) at which liquid changes to gas periodic trend(transition metals only)
▪ generally, melting and boiling points are directly related to # of unpaired e- in orbital
▪ more unpaired e- the higher the melting and boiling pts.
other elements dependent on various other factors
Where did the elements come from? https://www.youtube.com/watch?v=neMEo
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