Periodic Trends Flashcards
evolution of the periodic table
-daltons first list of elements in 1803 only had 5 elements, hydrogen, oxygen, azote(nitrogen), carbon, and sulfur
-arranged elements by their mass
John Dalton (~1810)
-Dalton’s 2nd list had 20 elements published in 1808
-many of his masses were not correct
-he designated a symbol to each number
Dmitri Mendelev (~1869)
-he recognizes patterns in the properties of elements and tries to arrange the table by those patterns (by mass)
-anything that repeats is called periodic such as (weather, sleep cycle
-his 1st periodic table was published in 1869
-this method left spaces in the table to be discovered later
Henry Moseley (~1911)
-realizes that the patterns correlate with the # of protons
-1st to arrange the table by atomic #
-he discovers the periodic law**
-his table still had holes but they were filled when other elements were discovered
Henry Moseley’s periodic law
the physical and chemical properties of the elements are periodic functions of their atomic numbers
Modern Periodic Table
-elements are odered by increasing atomic #
-elements with similar properties are in the same group
-each set of elements with similar properties has a name
Alkali Metals
group 1
-all end in s for e- configuration
-hydrogen is not one
-extremely reactive because they want to give away their 1 valance electron
Alkaline Earth Metals
group 2
-all end in s2 for e- configuration
-2nd most reactive metals
-they are called alkaline because they form a basic solution
Transition Metals
groups 3-12
-all have 2 valence electrons from the sublevel
-all elements with e-configuration ending in the d and f blocks
-the metals can take on many different charges
-the f block is often called inner transition metals
Lanthanides
1st row on the f-block (starts with lanthanum)
Actinides
2nd row of the f-block (starts with actinium)
Non-metals
-elements that arent metals
-to the right of the periodic table
Semimetals
-also called metalloids
-have properties of both metals and non-metals
Halogens
group 17
-have 7 valence electrons
-these are one electron away from having a full sub-level (so they are very reactive non-metals)
Noble gases
group 17
-nonreactive because they have a full sublevel
-noble gases have been forced to bond buy the don’t like to
Metals (characteristics)
(left side of the stair step line)
-usually solid at room temp and shiny
-malleable and ductile
-good conductors of heat and electricity
Non-metals (characteristics)
(right of the stair step line)
-usually gases at room temp
-brittle
-poor conductors of heat and electricty
Atomic Radius
size of the atom
atomic radius trends
-as you go down each group the radius goes up (higher energy levels are farther from the nucleus making the radius larger)
-as you go from left to right across each row the radius goes down (bc of the increased nucleur charge the e-‘s are stronger pulled towards the nucleus making the radius smaller)
Ionic Radius (cations)
cations are smaller than their neutral atoms bc they lose e-‘s. That means the electrons in their valence shell are lost
Ionic Radius (anions)
anions are bigger than their neutral atom because they gain electrons. this makes the e- repulsions greater and results in a bigger radius
Ionization Energy
-it is the amnt of energy it takes to knock an electron off
–the further out an electron is, the easier it is to steal (so it take less energy to do so
-the larger an atom is the lower its ionization energy
-trend is opposite of the radius trend
Ionization Energy trend
-across a row ionization e goes up bc the effective nuclear charge increases
-down a group i.e. goes down bc e-‘s are farther from the nucleus so they aren’t held as tightly and are easier to pull off.
Electronegativity
(mine) electronegativity is an element’s tendency to attract a bonding pair of electrons
-how selfish they are with the e-
