Chemistry : The Periodic table
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what purpose did the periodic talble bring?
organization of the elements. enables chemists to predict the existence of elements that aren't even discovered yet.
how many elements have scientists discovered by the end of the 1700's? what elements were they?
30. metals like copper, silver and gold.
what technique did scientists use to discover additional elements?
spectroscopy: elements are discovered in their line spectra.
what did the German Chemist, Dobereiner, observe in the early 1800's?
several elements could be classified into sets of three (triads)
what did Dobereiner's Triad include?
lithium, sodium, potassium and iodine.
use Dobereiner's triad to explain how chlorine, bromine and iodine have similar shemical properties.
35.5 (atomic mass of chlorine) + 126.90 (atomic mass of iodine / 2
= 81.2 (Bromine which is 79.9)
How did Newlands present and organized elements? (bonus: how many elements are known by his time?)
elements were arranged in order of increasing atomic mass. This pattern repeats every 8 elements. (Law of octaves)
What did Dmitri Mendeleev produce when he arranged the cards of the elements by increasing atomic mass?
what was his purpose on doing this?
he arranged his table so that elements in the same column have similar properties.
what did H.G.J moseley develop?
the concept of the atomic number.
"when elements are arranged in order of increasing atomic number, their physical and chemical properties show a periodic pattern."
the modern periodic table has how many squares?
what are the vertical groups/columns called?
groups or families.
what are the horizontal rows in the table called?
What elements are in group 1A? 2A? 7A? 8A?
alkaline earth metals
what are metals? where are they found in the periodic table?
good conductors of heat and electricity. usually solid in room temperature (exculding mercury)
far left side
what are non metals? where are they found in the periodic table?
do not possess a metallic luster. Poor conductors of heat and electricity.. mostly gases at room temperature.
far right side.
what are semimetals/metalloids?
acquire some properties of metals and metalloids.
what are valence electrons?
electrons that are responsible for an atom's chemical behavior.
s block elements?
how many electrons can each block hold?
s - 2
p - 6
d - 10
f - 14
what types of elements are in the s and p block?
what types of elements are in the d block?
what type of metals are in the f - block?
inner transition metals.
what are the four periodic trends?
- 1.) atomic radius
- 2.) ionic radius
- 3.) ionization energy
- 4.) electronegativity
what is the atomic radius?
the distance from the center of an atom's nucleus to its outermost electron.
if an atom is going down a group, what is happening?
it is getting larger. ionization energy decreases
if an atom is going from the left to right, that is happening?
getting smaller ionization energy increases
true or false: some ions are more common than others.
what is ionic radius?
size of element's ion
if an elements loses electrons (becomes positive ions) it becomes....
is an element gains electrons (becomes negative ions) it becomes...
what is an ionization energy?
the energy needed to remove one of its electrons.
how many joules are required to remove 1 electron from a lithium?
8.64 x 10 ^ -19
what is joules? (J)
the SI unit for energy.
how do atoms hold onto their electrons if it has high ionization energies?
atoms with low ionization energies will...
lose one or more of their electrons and gain a positive charge.
equation of mole?
6.02 x 10 ^ 23
what is ionization energy?
the energy to remove the first electron from an isolated atom
what is electron affinity?
the energy change that occurs when it gains an extra elctron.
what is electronegativity?
reflects its ability to attract electrons in a chemical bond.
what is the most electronegative elements?
flourine. it has an electronegativity of 4.0
how are the trends of ionization energy and electronegativy similar?
both increase as you move from left to right across a period and decrease as you move down a group.
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