dmitri mendeleev 1834 - 1907 in 1869 he published a table of the elements organized by increasing...
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Dmitri Mendeleev
1834 - 1907
In 1869 he published a table of the elements organized by increasing atomic mass.
Henry Moseley
1887 - 1915
In 1913, through his work with X-rays, he determined the actual nuclear charge (atomic number) of the elements*. He rearranged the elements in order of increasing atomic number.*“There is in the atom a fundamental quantity which increases by regular steps as we pass from each element to the next. This quantity can only be the charge on the central positive nucleus.”
Review!
• What group number are the Halogens found in?
Review!
• What special group is Sodium a part of?
Review!
• Is Chlorine a metal or a nonmetal? How do you know?
Periodic Law or Periodicity: The arrangement of the elements in
order of their atomic numbers so that elements with similar properties fall in
the same column, or group.
The horizontal rows of the periodic table are called PERIODS.
The vertical columns of the periodic table are called GROUPS, or FAMILIES.
The elements in any group of the periodic table have similar physical and chemical properties!
Electron Configuration and the Periodic Table
– The s-block Elements: Groups 1 and 2• Group I: Alkali metals-all elements in this group
have one electron in their outer energy level. ns1
•Group II: Alkaline earth metals-all elements in this group have two electrons in their outer energy level. ns2
Hydrogen and Helium-the Oddballs
The p-block Elements: Groups 13-18 (except He)
Contains metals AND nonmetals AND metalloids along the zigzag line (boron, silicon, germanium, arsenic, antimony, and tellurium)
Group 17- Halogens-the most reactive nonmetals
How many valence electrons do the halogens have?
b.
The Noble gases-
He, Ar, Kr, Xe, Rn-very unreactive
Why are the noble gases so unreactive?
The f-block Elements:
• Lanthanides-numbers 58-71; the transition elements
• Actinides-number 90-103; the inner transition elements
Also known as the inner transition metals
The d-block Elements: Groups 3-8
Also known as the transition metals
Some deviations occur in the d-block because the s and d energy levels are so close together
sd d dd d
The d-block Elements: Groups 3-12
Irregular Electron configurations – sometimes the electron configuration is NOT what we would predict it to be. Sometimes electrons are moved because (l) it will result in greater stability for that atom or (2) for
some unknown reason??
Stability:
Example: Group 6: Chromium, Molybdenum, Tungsten
Cr:NOT [Ar]4s23d4 instead [Ar] 4s13d5
Example: Group 9: Copper, Silver, Gold
Cu: NOT [Ar]4s23d9 instead [Ar] 4s13d10
Other exceptions exist, but these are the main ones.
Valence Electrons-
• electrons available to be lost, gained, or shared in the formation of chemical compounds. Valence electrons are in the outer s and p energy level of representative atoms – All Group A elements.
• In the transition elements, valence electrons are in d and f sublevels that are not full or half full.
Octet Rule
• In chemical bonding, atoms will give, share, or take electrons to have a full outer energy level. For all elements except H, a full outer energy level will have eight electrons, (hence the name “Octet” rule). Hydrogen’s full outer energy level will have 2 electrons.
On your periodic table, let’s label the valence electrons and oxidation number trends!
Valence e-: 1 2 3 4 5 6 7 8
Oxidation #: +1 +2 +3 +4 -3 -2 -1 0
Review Time!
• Which group has 2 valence electrons?
• What is that group’s special name?
Review Time!
• Which group is NONREACTIVE?
• Why?
Review time!
• Would Cesium react (have similar chemical properties) like Lithium or Barium?
• Why?
Periodic Trends!
Atomic Radii-• defined as one-half the distance between the
nuclei of identical atoms that are bonded together.
– periodic trends- atoms get smaller as you go from left to right because of an increasing positive charge of the nucleus
– group trends- radii get larger down a group because of electrons occupying more energy levels and sublevels
Atomic Radius Explained!
Now draw your trend lines on your P.T.!
Atomic & Ionic Radius
Which has the greater atomic size, C or O?
Which has the greater atomic size, C or O?
• Atomic size increases down a column because orbitals of higher quantum number (n) have their maximum probability farther from the nucleus. Atomic size decreases from left to right in the periodic table because the greater number of protons in the nucleus will exert a greater attraction on the electrons, pulling them closer to the nucleus.
Which has the greater atomic size, Li or K?
Which has the greater atomic size, Li or
K?
• Atomic size increases down a column because orbitals of higher quantum number (n) have their maximum probability farther from the nucleus. Atomic size decreases from left to right in the periodic table because the greater number of protons in the nucleus will exert a greater attraction on the electrons, pulling them closer to the nucleus.
Learning Check!
• Is a barium atom larger or smaller than a strontium atom?
• If a halogen and an alkali metal are in the same period, which element will have the larger atomic radius?
• Compared to the atomic radius of a sodium atom, the atomic radius of a magnesium atom is smaller. The smaller radius is primarily a result of the magnesium atom having…?
Size of Ions (Ionic Radii)
A Positive ion is a cation after it has lost an electron(s) (Ca+2, Cs+1)
A negative ion is an anion after it has gained an electron(s) ( Br-1, O-2)
I think cats are a positive force! Therefore… CATions are positive
ions!
Size of Ions (Ionic Radii)
• Cations (Na+1, Ba+2) are SMALLER than the original ion (Na, Ba)
•
• Anions (Cl-1, S-2) are LARGER than the original ion (Cl, S)
Metals LOSING electrons
•For each of the Group 1 metals below, the ion is much smaller than the atom.
– When an atom loses an electron, it loses it from it’s outer energy level.
– As a result, the remaining electrons are drawn closer to the nucleus.
– ion has one fewer occupied energy level and therefore, takes up less space.
Nonmetals GAINING electrons
•For each of the Group 17 nonmetals below, the ion is much larger than the atom.
– As the number of electrons increases, the attraction of the nucleus for any one electron decreases.
– As a result of adding more electrons, the ion takes up MORE space
Learning Check!
• Is a sodium atom (Na) larger or smaller than a sodium ion (Na+)?
• In general, how does ionic radius vary from top to bottom within a group?
• Which element will form an ion whose ionic radius is larger than its atomic radius? K, F, Li or Mg
Ionization energy-the energy required to remove
one electron from a neutral atom of an element
– periodic trends- increase across the period because of increasing nuclear charge
– group trends- decrease down the group because electrons are farther away from nucleus.
Now draw your trend lines on your P.T.!
Atomic & Ionic Radius
ION. ENERGY
Learning Check!• Would it be easier to remove an electron
from a boron atom or from an aluminum atom?
• Would it be easier to remove an electron from a boron atom or from a carbon atom?
• Low ionization energies are most characteristic of atoms that are….?
Which has the higher ionization energy, Mg or P?
Which has the higher ionization energy, Mg or P?
• From left to right in a period, ionization energy increases the closer the element gets to a noble gas configuration.
P
Which has the higher ionization energy, As or Sb?
Which has the higher ionization energy, As or Sb?
• Ionization energy decreases down a group because the electrons in high quantum number orbitals are held less strongly by the nucleus than are electrons in low-n orbitals.
As
Electronegativity-a measure of the ability of an atom in a chemical
compound to attract electrons.
– periodic trends- EN tends to increase across each period because of greater nuclear charge in the atom
– group trends- decrease or stay the same down a group
– Does not apply to noble gases
Electronegativity (EN)EN: a measure of the ability of an atom in a chemical compound to attract electrons.
periodic trends- increase across each period because of greater nuclear charge in the atomgroup trends- decrease or stay the same down a group. Does not apply to noble gases
Now draw your trend lines on your P.T.!
ELECTRONEG.
Atomic & Ionic Radius
ION. ENERGY
Learning Check!
• Which element in the periodic table is the most electronegative? Which element is the least electronegative?
• The halogen with the highest electronegativity is….?
In summary…
D.The metallic character trends explain the location of metals,
metalloids, and nonmetals
Which is the more metallic element, Sn or Te?
Which is the more metallic element, Si or Sn?
Reactivity of metals
• How reactive are metals within a group? The further down the group, the more reactive the metal. Remember the video – as you go down the alkali metals group, the bigger the explosion. Sounds like
Cesium!!
