Transcript Periodic Properties of Elements

Periodic Properties of Elements
1869 First Modern Periodic Table
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Mendeleev
Arranged by atomic weight
Modern atomic numbers
Atomic number = number of protons in the atom
Mass number = the number of protons and
neutrons in the atom
• Mass number - the atomic number = the amount
of neutrons in the atom
• Number of electrons = (usually) same number as
protons so it is neutral
How to distinguish between mass
numbers and atomic numbers
Periodic Table of Properties
• Vertical = families, groups, labeled IA – 2B
• Horizontal –periods, series 1,2,3,4 --1A –Alkali Metals
2A -Alkali Earth
7A –Halogen
8A –Noble gasses
A group = representative elements
B group = transition elements
Electrons
• number of valance electrons
• A group = main group = group number
(columns)
• 1A means the atom has 1 valance electron
• 2A means the atom has 2 valance electrons
Metals and nonmetals
• metallic nature –metal- silvery or gray, high
density, solids, high melting and boiling point,
good conductors of heat and electricity,
malleable, ductile-thin wires drawn out, Al, Ge,
Sb, Po
• Nonmetal –solid liquid or gas
lower melting pts than boiling pts,
lower densities, poor conductors of heat and
electricity, brittle as solids, B, Si, As, Te, At
Al, Ge,Sb,Po, B, Si,As, Te,At are considered
metaloids
Metalloids
• Between metals and non-metals, some
properties of metals, some of non-metals,
some have neither
Metallic Nature
• A, Main group of elements only
-down a group = increased metallic nature
-across a period = decreases in metallic nature
11Na vrs 19K = K is more metallic in nature
20Ca vrs 31Ga = Ca is more metallic in nature
19K vrs 12Mg = K is more metallic in nature
11Na vrs. 20Ca = they are equal in metallic nature
Atomic size in the quantum model
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The outer edge of an atom is fuzzy like a cloud
The cloud fades away
The electron is in the cloud which is an orbital
Electron cloud
In a bond where atoms share an electron
between them, the distance between the two
nuclei determines the covalent radius of
atoms
Atomic size
• Down a group = atomic size increases
• Across a period = atomic size decreases
Ionization property
• Energy required to remove an electron from a
neutral gaseous atom
• 11Na
e- = 11Na+ = no longer has a
balanced charge and is not neutral = ion
Na still has 11 positive protons but now has
only 10 negative electrons = now has a
positive charge.
• The more an atom loses electrons, the more it
will try to hold to what it has left
• It takes more Ionization energy to pull off the
next electron from the atom
• 11Na
e- e- = 11Na+2
• Na could have up to 11 ionization energies
with each one being stronger than the
previous
• Down a group = 1st ionization energy
decreases
• Across a period 1st ionization energy increases
regularly