S3.1 Flashcards
periodic table
arrangment of elements in the periodic table
- elements are arranged according to their atomic number (Z)
- vertically arranged into groups (1-18) ⇒ elements with the same number of valence electrons, hence, chemical and physical properties
- horizontally arranged into periods (1-7) ⇒ number of principal energy levels
- elements are arranged into 4 blocks associated with the 4 sublevels (s, p, d, f)
groups of the periodic table
group 1 = alkali metals
group 2 = alkaline earth metals
groups 3-14 = transition metals
group 15 = pnictogens
group 16 = chalcogens
group 17 = halogens
group 18 = noble gases
group 1
- alkali metals
- extremely reactive (reactivity increases down the group)
- soft
- Li, Na, K have lower density than water
- low melting and boiling points (decrease down the group)
- react with water ⇒ create hydroxides ⇒ stored in oil to prevent reactions with oxygen and moisture in the air
group 17
- halogens
- reactive non-metals
- melting and boiling points increase down the group
- diatomic molecules
- reactivity decreases down the group
- a halogen will react with a solution of halide ions, formed by a less reactive halogen (more reactive halogen molecule + less reactive ion) ⇒ the halogen displaces the ion
properties of metals
good conductors of electricity and heat
malleable, ductile, lustre
act as reducing agents
most often form cations
properties of non-metals
do not conduct electricity
act as oxidising agents
most often form anions
properites of metalloids
metallic and non-metallic properties
semiconductors ⇒ their conductivity relies on temperature
“tightness of hold” on electrons - trend of the periodic trend
Across the period (to the right) ⇒ higher effective nuclear change with the same number of principal energy levels → electrons are held tighter
Down the group ⇒ growing number of principal energy levels → larger orbitals, electrons held looser, shielding effect
effective nuclear charge
the net positive charge experienced by outer valence shell electrons from the force of attraction between protons in the nucleus and the force of repulsion between inner core electrons
atomic radius
- = the distance from an atom’s nucleus to the outermost orbital of one of its electrons
- usually measured as half of the distance between the nuclei of two of the same atoms bonded together (metals - half the distance between two atoms adjacent to each other in the crystalline lattice, noble gases - half the distance between two nuclei of atoms in a frozen gas)
- the electron cloud has no definite edge
atomic radius is influenced by
- energy level ⇒ higher energy levels are further away
- charge on nucleus ⇒ more charge pulls electrons closer to nucleus
- shielding effect ⇒ core electrons in inner non-valence levels of the atom reduce positive nuclear charge experienced by valence electrons
net charge experienced by an electron
Zeff = Z - S
Z … atomic number, actual charge
S … shielding constant
trends in atomic radius across the periodic table
down a group ⇒ each atom has an additional energy level → atoms get bigger
across a period ⇒ electrons are in the same energy level, larger effective nuclear charge → outermost electrons are closer → smaller radius
ionic radius of cations and anions
Cations ⇒ smaller than the original atom (as a result of losing electrons)
Anions ⇒ larger than the original atom (as a result of gaining electrons)
less electrons => smaller
ionic radius of ions of transition elements
ions of non-transition metals have noble gas configurations (isoelectronic with them)
down a group ⇒ ionic radius of ions increases
across a period ⇒ nuclear charge increases → ionic radius decreases, even with energy level differences
ionic radius of isoelectronic ions
positive ions with the most protons are smaller
losing electrons is an endo or exothermic reaction?
endothermic
do filled and half-filled orbirals have higher or lower energy? how does this affect IE?
filled and half-filled orbitals have lower energy ⇒ lower IE
IE down a group, across a period
down a group ⇒ electron is further away from the nucleus, more shielding → decreased first IE
across the period ⇒ atoms have the same energy level and shielding, nuclear charge is increasing ⇒ increased first IE
electron affinity
def, reaction, exo/endothermic, unit
= energy change associated with the addition of a mole of gaseous electrons [kJ/mol]
X (g) + e– → X– (g) ⇒ exothermic reaction
trend in electron affinity across the period and down the group
across the period ⇒ greater nuclear charge → atoms are smaller → increased electron affinity
down the group ⇒ electrons are in higher energy levels → atoms are larger → decreased electron affinity
what is the electron affinity of nobel gases?
positive
electronegativity
= tendency of an atom to attract electrons to itself when chemically combined with another element (i.e. how strong electrons are attracted to the nucleus)
higher electronegativity ⇒ pulls electrons towards itself
atoms with higher electronegativity also have negative electron affinity
trends across a period and down a group with electronegativity
down a group ⇒ decreased electronegativity
across a period ⇒ increased electronegativity
trend in metallic character across the period, down the group?
across the period ⇒ decreases
down the group ⇒ decreases
lewis acids and baces
Lewis acid ⇒ accepts electron pair
Lewis base ⇒ donates electron pair
trend of increasing acidic character across a period
increasing acidic character across a period due to greater nuclear charge, pulling electrons closer (less likely to give them away)
amphoteric substance
able to react as both an acid and base (f.i. Al2O3)
classifications of acids + naming
- binary acids ⇒ hydro- + non-metal atom + -ic acid
- oxyacids ⇒ anion:-ate, acid: -ic; anion: -ite, acid: -ous OR -ate/-ic form with oxidation number
- organic acids
hydrofluoric acid
HF
binary acid
fluoride
F-
anion
hydrochloric acid
HCl
binary acid
chloride
Cl-
anion
hydroiodic acid
HI
binary acid
iodide
I-
anion
iodic acid
HIO3
oxyacid
iodate
IO3-
anion
hydrosulfuric acid
H2S
binary acid
sulfide
S(2-)
anion
nitrous acid
HNO2
oxyacid
nitrite
NO2-
anion
nitric acid
HNO3
oxyacid
nitrate
NO3-
anion