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