Chemistry unit 4
Atomic radius
Half the distance between the nuclei of two chemically bonded atoms
Anion
Product of an atom gaining an electron
Kilojoules
Units used to measure ionization energy and electron affinity
What is the trend in attomic radii when one moves left in a period
it gets smaller as you go to right, more protons means more pull
Mendeleev
Created the first periodic table in 1869 where elements were arranged by atomic mass
Halogens
Group 17
Noble gas
Group 18
S block elements
Groups 1-2 (chemically reactive metals)
Transition metals
Groups 3-12
Shielding
Inner electrons blocking nuclear pull on valence electrons
Metalloids
Semiconducting elements that are shiny but brittle
Electronnegativity
A measure of the ability of an atom in a chemical compound to attract electrons
Metallic character
A relative measure of how easily atoms lose or give up electrons
Periodic table
An arrangement of the electrons in order of their atomic numbers so that elements with similar properties fall in the same column, or group
Ionization
Any process that results in the formation of an ion
Why do atoms get LARGER as you move DOWN within the same group on the periodic table?
Atoms gain more energy levels as they go down a group. More energy levels=bigger
Why do atoms get SMALLER as you move RIGHT within the same period on the periodic table?
Atoms have more protons, which means positive nucleus, electron cloud gets negative so there's an increased attraction
Ions
Atoms that have gained or lost electrons
Cannizzaro
Developed a standard method for measuring the atomic masses of atoms
Pauling
Developed an arbitrary scale that ranges from 0-4
Nonmetals
Dull, brittle, insulating elements
Main groups
Elements in the s and p blocks
Endothermic
Energy added to an atom results in this type of process
Exothermic
Energy released from an atom results in this type of process
Alkali metals
Group 1
Alkaline earth metals
Group 2
P block elements
Groups 13-18 (except helium)
D block elements
Groups 3-12 (transition metals)
Periods
Horizontal row on the periodic table; corresponds to energy levels
Berzelius
Introduced letters to symbolize elements
F block elements
Located between groups 3&4 in the 6&7 periods; lanthanides
Cation
Product of an atom losing an electron
Moseley
Rearranged the periodic table by atomic number
Metals
Shiny, malleable, ductile elements that are good conductors of heat and electricity
Prout
Stated that H was the fundamental element from which all others were composed
Newlands
Suggested the Law of Octaves
Debereiner
Suggested the existence of triads in terms of properties of elements
Periodic law
The chemical and physical properties of the elements are a periodic function of their atomic number
Electron affinity
The energy change that occurs when an electron is acquired by a neutral atom
Ionization energy
The minimum energy required to remove one electron from a neutral atom of an element
Fluorine
The most electronegative element on the periodic table with a value of 4
Periodic trends
Used to classify the arrangement of elements on the periodic table
Groups
Vertical columns on the periodic table
SUBLEVEL affect ionization energy
an electron from a sublevel that is more than half full requires additional energy to be removed
Period trend of electronegativity
going from left to right across a period, the electronegativity increases
Group trend of electronegativity
going from top to bottom down a group, electronegativity decreases or stays the same
What is the trend in atomic radii when one moves down a group
it increases because more electrons, needs larger atom bcuz more energy levels
Period trend of metallic character
metallic character of an atom decreases as you go from left to right across a period on the periodic table
Group trend of metallic character
metallic character of an atom increases as you go from top to bottom down a group on the periodic table
Why does the electronegativity increase as you go across a period
the electrons are close to the nucleus so it's easier for electrons to get pulled in, there's a greater pull and they're closer to stability
Why does the electronegativity decrease as you go down a group
the electrons aren't pulled closer so it's harder to attract electrons and electronegativity is lower
RADIUS affect ionization energy
the greater the distance between the nuclei and the outer electrons of an atom, the less the ionization energy
SHIELDING EFFECT affect ionization energy
the greater the shielding effect, the less the ionization energy
NUCLEAR CHARGE affect ionization energy
the larger the nuclear charge, the greater ionization energy
Are anions larger or smaller than their respective atoms
they're larger because gaining electrons means more electrons than protons
Are cations larger or smaller than their respective atoms
they're smaller because they're losing electrons
