Chapter 5 Flashcards
What did Dobereiner do?
observed that elements could be classified into sets of three called TRIADS
triads
a group of three elements with similar chemical properties
What did Newlands do?
created the law of OCTAVES
law of octaves
when elements are arranged in order of increasing atomic mass, the properties of the eighth element are similar to the properties of the first, the ninth like the second, etc
What did Mendeleev do?
noticed that when elements were arranged in order of increasing atomic mass, certain similarities in their chemical properties appeared in regular intervals
periodic
repeating patterns
Why does Mendeleev get credit for the periodic table?
organized the table by grouping elements with similar properties, left a few spots blank, and accurately predicted the properties of these unknown elements
What did Moseley do?
discovered elements fit into patterns better when they were arranged according to atomic number rather than atomic weight
periodic law
physical and chemical properties of elements are periodic functions of their atomic numbers
periodic table
arrangement of elements in order of their atomic numbers so that elements with similar properties fall in the same columns or groups
elements arranged in groups
have similar chemical properties
length of period
determined by number of electrons that can occupy the sublevels filled in that period
blocks
s,p,d,f; determined by electron sublevel being filled in that block
alkali metals
group 1 elements, most reactive metals, silvery appearance, soft
alkaline earth metals
group 2 elements, less reactive than alkali but too reactive to find in nature in pure form
Hydrogen
electron config of 1s^1 but does not share properties as group 1
Helium
in group 18 because it’s nonreactive
transition elements
d-block elements, typically metallic properties, 3 through 12
p-block elements
groups 13 through 18, except for Helium
main group elements
s and p block elements
p block elements
right side is all nonmetals but Hydrogen and Helium, all six metalloids are in p block, left and bottom are eight p block metals
p block element properties
vary greatly
halogens
group 17, most reactive nonmetals, react with most metals to form compounds known as salts
Flourine
most reactive nonmetal
metalloids
semiconducting elements located between nonmetals and metals in p block
p block metals
harder and denser than s block alkaline earth metals but softer and less dense than d block metals
f block
wedged between groups 3 and 4 due to them filling 4f sublevel
lanthanides
first row of f block, shiny metals similar in reactivity to group 2 alkaline earth metals
periodic trend
property of an element that can be predicted from the arrangement in periodic table
atomic radius
distance from center of atom’s nucleus to outermost electron
How to increase atomic radius?
going right to left across period and down periods
cation
atom loses electrons and becomes smaller, positive charge
anion
atom gains electrons and becomes larger, negative charge
Why does an atom get smaller when losing electrons?
losing electrons increases positive force which then pulls electrons closer to nucleus and reduces radius
octet rule
atoms tend to gain, lose, or share electrons in order to acquire a full set of valence electrons
octet
set of eight
valence electrons
electrons on outermost energy level
When are atoms stable?
when they have eight valence electrons
ionization energy
energy needed to remove an electron
When does ionization energy increase?
as you move from left to right and up periods
successive ionization energies
energy needed to remove a second, third, fourth, etc electron
Why does successive ionization energy increase?
removing electrons makes a positive ion which makes it harder to remove electrons
When does a jump in ionization energy occur?
when an electron is pulled from the noble gas core
electronegativity
atom’s ability to attract electrons in chemical bond
When does electronegativity increase?
as you move left to right and up a period
electron affinity
energy change that occurs when an atom gains an extra electron
electron affinity
energy change that occurs when an atom gains an extra electron
When does electron affinity increase?
as you move left to right across period and up a period
