periodic trends Flashcards
(21 cards)
atomic radius
distance of an atom from its nucleus to the outermost electron
atomic radius across a period
From left to right across a period the net attraction force of the nucleus to each electron increases as the number of protons in the nucleus increases.
a greater force of attraction means a smaller distance between the nucleus and valance electrons and a smaller atomic radius.
atomic radius down a group
from top to bottom down a group the number of energy levels increases.
more energy levels result in a larger atomic radius
ionisation energy
amount of energy required to remove one electron from a single atom in the gaseous phase
ionisation proportionality
inversely proportional to atomic radius
ionisation energy across a period
from left to right across a period the net. attraction force of the nucleus to each electron increases as the number of protons in the nucleus increases.
A strong force of attraction means a smaller distance between the nucleus + valence electron and a smaller atomic radius.
A strong force of attraction means that more energy is required to overcome force to remove one electron
ionisation energy down a group
from top to bottom down a group the number of energy levels increases (increasing atomic radius).
valence electrons are increasingly shielded from the positive nucleus by core electrons .
This results in a weaker force of attraction on each electron means that less energy is required to overcome
a weak force of attraction means that less energy is required to overcome forces to remove electrons
electron affinity
the amount of energy liberated when an electron is added to a single atom in the gaseous phase
electron affinity across a period
from left to right across a period the number of protons in the nucleus increases.
The attraction for an electron increases.
More energy is released when an electron is added
electron affinity down a group
from top to bottom down a group the number of energy levels increases (increasing atomic radius).
More energy levels means more electron shielding of positive nucleus .
The attraction for an electron decreases .
Less energy is released when an electron is added
electronegativity
the ability of an atom to attract bonding pairs of electrons
density
mass per unit volume
mass/volume
non metals are less dense than metals
density across a period
from left to right across a group density increases
atomic radius decreases
atomic mass increases
density down a group
from top to bottom down a group density increases
atomic radius increases
atomic mass increases substantially
melting point
the temperature at which a solid changes phase to a liquid
boiling point
the temperature at which a liquid changes phase to a gas
melting and boiling point trends
metals group 1-14 (left to right) increases
non metals group 15-18(left to right) very low
metals group 1 +2 (top to bottom) decreases
non metals group 17+18 (top to bottom) increases
properties of group 1
alkali metals
most reactive - have single valance e- which is easily lost
found in compounds
soft and light grey
react w cold water
properties of group 2
alkaline earth metals
reactive - 2 valance e-
react w cold water,light grey,soft,good conductors (except Be)
properties of group 17
halogens
very reactive
form salts
7 valence e-
found in compounds
low melting points
properties of group 18
nobles gases
unreactive
gases at room temperature
