Vertical column - group
8 groups(I to VIII), 18 vertical columns
14 columns -Â subgroups for groups I to VII
3 columns - group VIII
1 column - zero group elements
Sub group A(1, 2, 13, 14, 15, 16, 17) - Normal/Representative elements(outermost shell incomplete)
Sub group B(3, 4, 5, 6, 7 ,8 ,9, 10, 11, 12) - Transition elements(two outermost shells incomplete)
Inner transition elements - lanthanide and actinide series
Alkali metals - most reactive metals(react violently with water to form hydrogen and alkali solution)
Alkaline earth metals - form bases
Halogens - most reactive nonmetals(form acids with hydrogen and salts with metals)
When elements are arranged in the order of increasing atomic number, the characteristic properties of elements reappear at regular intervals.
Periodic properties - Characteristic properties of elements which occur at definite intervals
PROPERTIES
- Atomic Radii
- Distance between nucleus and outermost shell of atom
- Unit: angstrom unit
- No.of shells(more shells, increased radii)
- Nuclear charge - positive charge present in the nucleus
- Greater nuclear charge, lesser atomic radii
Depends on:
- Increase in a group from top to bottom(more shells, less ENC)
- Smallest atomic radii: Helium
- Ionisation Potential
- Amount of energy absorbed/required to remove one or more electrons from the valence shell of an atom of an element
- Expressed in eV(electron volt)
- First Ionisation potential is the least
- Members of group 18 have highest ionisation potential
- Decreases from going top to bottom in a group(increase in shells = less effect of enc)
- Larger the atomic radii, lower the IP
- Factors affecting: Nuclear charge, atomic size
- Increases across period
- Decreases down group
- Highest IP = helium
- Lowest ip = caesium
- Electron Affinity
- Amount of energy released when one or more electrons are added to the outermost shell of an atom of an element
- Expressed in eV(electron volt) with -ve sign
- Smaller atom = greater ea(higher forces = hold atoms with more force)
- Greater nuclear charge = greater ea
- Noble gases = 0 electron affinity
- Highest ea = halogens
- Lowest ea = alkali metals
- Decreases down group
- Increases across period
- Reducing elements on the left, oxidising elements in the rights
- Alkali metals: strong reducing agents
- Halogens: strong oxidising agents
- Metallic Character
- Ease with which an element loses electrons
- Becomes electropositive
- Common characteristic among metals
- Greater atomic radii = greater metallic character
- Decreased ip = increased mc
- Elements at the bottom of the group are most metallic
- Reactivity of metals increase down group
- Decreases across period
- Non-metallic character
- Ease with which an atom of an element gains one or more electrons and becomes electronegative
- Common in non metals
- Small atomic radii = higher non metallic character
- Increased ip = increased non metallic character
- Decreases down group
- Increases across period
- Electronegativity
- Tendency of at atom to attract electrons to itself when combines in a compound
- Wide difference in electronegativity: ionic bond
- Small difference in electronegativity: covalent bond
- Non-polar covalent: shared atoms exactly midway
- Polar covalent: shared pair of electrons attracted towards one element(partial + and - charges)
- Small atomic size = more electronegative
- Greater nuclear charge = more electronegative
- Decreases top to bottom in a group
- Increases across period
- Low electronegativity is a characteristic of metals
- High electronegativity is a characteristic of nonmetals
- Most electronegative: fluorine
- Least electronegative: Caesium
Noble gases, lanthanides, actinides: no electronegativity values(ng: full valence shell, lanthanide actinide: complex chemistry = no follow trends)
Little variance between en values of transition metals(metallic property affects ability to attract electrons)
Melting boiling metals: decrease down group,
Melting boiling non metals: increase down group
Density: increase down group
Oxides: acidic to basic down group
Hydroxides: less basic to strongly basic down group
Oxyacids: strong acid to weak acid down group
Hydrides: Less acidic to more acidic down group
MP/BP across group - increases upto group 14, slight decrease
Density - increase to maximum, slight decrease across periods
Oxides across group: basic to amphoteric to acidic
Hydroxides across group: strongly basic to amphoteric to acidic
Oxyacids across group: weak acids to strong acids
Hydrides across group: strongly basic to strongly acidic