Unit 3: Periodicity Flashcards
Properties of Metal
- usually a solid @ room temp (except Hg)
- shiny/lustrous
- malleable: can be hammered into sheets
- good conductors of heat + electricity
- high m.p.
- ductile: can be drawn into wires
- lose e-
- low values for electronegativity, ionization energy, and electron affinity values
Properties of Nonmetals
- dull/lack luster
- poor conductor
-insulator of heat + electricity - gain e-
- high values for electronegativity, ionization energy, and electron affinity values
Properties of Metalloids
- Have characteristics of both metals & nonmetals
- Physical properties/ appearance resemble metals
- Chemical properties resemble nonmetals
Periods
Horizontal Rows (1-7)
Groups
Vertical columns (1-18)
- sometime groups 3-12 are “omitted” and we call the remaining groups, Groups 1A-8A
Group 1
Alkali metals
Groups 3-12
Transition metals (d-block)
Group 17
Halogens
Group 18
Noble gasses
Elements 58-71
Lanthanoids (f-block)
Elements 90-103
Actinoids (f-block)
Atomic Radius (group-trend)
As you move down a group, atomic radius increases
(“snowman effect”
Why does atomic radius increase as you move down a group?
As the # of occupied energy levels increases, so does the size of the atom
Atomic Radius (period-trend)
As you move across a period, atomic radius decreases
Why does the atomic radius decrease as you move across a period?
Same: e- are being added to the same energy level
Different: the # of protons increases so the attraction between the increasingly positive center and (-) e- increases. This attraction “pulls in” the outer e-
Ionic Radius (Cations) (Group)
Cations increase in size down a group as the outer energy level gets further from the nucleus (less attraction)
Ionic Radius (Cations) (Period)
Cations in a period contain the same # of e- but an increasing # of protons, creasing the attraction between the (+) center and the (-) e-. thus decreasing the radius
Ionic Radius (Anions) (Group)
Anions increase in size down a group as the outer energy level gets further from the nucleus (less attraction)
Ionic Radius (Anions) (Period)
Anions in a period contain the same # of e- but an increasing # of protons, increasing the attraction between the (=) center and the (-) e-, thus decreasing the radis
First Ionization Energy (definition)
The energy required to remove one electron from an atom in its gaseous state
Ionization Energy (Group) (Trend)
As you move down a group, ionization energy decreases
Why does the first ionization energy decrease as you move down a group?
The # of occupied energy levels increases, so the increased distance between the e- and the nucleus reduces the attraction (lower I.E. makes it easier to remove e-)
Ionization Energy (Period) (Trend)
As you move across a period, ionization energy increases
Why does the first ionization energy increase as you move across a period?
The extra e- are filling the same energy level, but the extra protons in the nucleus attract the energy level close making it harder to remove an e- (increasing I.E.)
Electronegativity (definition)
A measure the ability to attract electrons in a covalent bond
Electronegativity (Group) (Trend)
As you move down a group, electronegativity decreases
Why does electronegativity decrease as you move down a group?
The bonding e- (outermost e-) are getting father from the nucleus and so there is reduced attraction
Electronegativity (Period) (Trend)
As you move across a period electronegativity increases
Why does electronegativity increase as you move across a period?
There is an increase in # of protons, resulting in an increased attraction between the nucleus and the bounding e-
Electronegativity (Noble gasses)
no values
no desire to attract an e-
Electron Affinity (definition)
The energy change when an electron is added to an isolated atom in the gaseous state
Metalloids
B, Si, Ge, As, Sb, Te, Po
Melting Point
depends on the structure of the element and the type of attractive forces which hold the atoms together
Melting Point (Metals)
exhibit metallic bounding (ex. Na, Mg, Al) which increase in strength as the # of valence e- increases
Melting Point (Silicon)
The metalloid has a “unique” covalent structure with very strong bonds resulting in high m.p.
Melting Point (Nonmetals)
P, S, Cl have a simpler molecuar structures with weak forces of attractions
Melting Point (Ar/noble gasses)
exist as monatomic molecules (single atoms) with extremely weak forces of attraction between the atoms
Melting Point (Group 1)
m.p. decreases down the group as the atoms become larger and the strength of the metallic bond decreases
Melting Point (Group 17)
Halogens are held together by London dispersion forces. These get stronger as the number of electrons in the molecule increases
Alkali metals
- very reactive metals
- readily lose e- (low I.E.)
-Chemical reactivity increases as you go down the group since less E is required to remove the e-, aiding in a faster/more vigorous reaction
Halogens
- very reactive non-metals
- Exist as diatomic molecules
- react by gaining an e-
- Reactivity decreases as you go down the group as the outer shell gets further from the nucleus, decreasing the attraction for another e-
Most reactive metal
Francium
Most reactive nonmetal
Fluorine
Acid
- starts w/ H
- lots of H+
(0-7)
Basic
- end w/ OH
- lots of OH- (hydroxide)
(pH>7)
Period 3
basic-> amphoteric -> acidic
