Trends in Atomic Radii, Electronegativity and Ionisation Energy Flashcards
Atomic radii decreases….
across a period
Explanation for atomic radii decreasing
- across a period, successive valence e- are being added to the SAME ENERGY LEVEL while the number of protons is STEADILY INCREASING
- individual valence electrons experience attraction to the increasing number of protons
- therefore they’re PULLED CLOSER to the nucleus and the VALENCE SHELL contracts
Atomic radii increases…..
down a group
Explanation for atomic radii increasing
- down a group, valence e- are being added to SUCCESSIVE HIGHER ENERGY LEVELS
- each successive energy level is FURTHER FROM THE NUCLEUS
- due to this increased distance, the electrostatic attraction between the protons and e- DECREASES, WIDENING THE RADIUS
- inner e- shells also SHEILD THE NUCLEUS and cause e-/e- REPULSION, pushing outer e- further from the nucleus, INCREASING RADII
Are cations bigger or smaller than their parent ion?
smaller
Why are cations a different size to their parent ion?
- Cations have a smaller radius because they LOSE ONE OR MORE e- from their valence shell (or they lose an ENTIRE ENERGY LEVEL)
- therefore there is GREATER ATTRACTION between the nucleus and the REMAINING e-, drawing the outer e- CLOSER TO THE NUCLEUS
- there is also LESS e-/e- REPULSION between remaining e-
- therefore the cation is SMALLER than its parent ion
Are anions bigger or smaller than their parent ion?
bigger
Why are anions a different size to their parent ion?
- anions have a LARGER RADIUS because they GAIN ONE OR MORE e- into their valence e- shell/ outer energy level
- therefore there is GREATER e-/e- REPULSION, forcing the outer e- AWAY from the NUCLEUS
Electronegativity decreases….
down a group
Explanation for electronegativity decreasing
- what factors affect it: nuclear charge (more protons, the stronger the attraction it will have to e-); number and location of other e- in the atomic shells
- e- are added to SUCCESSIVE HIGHER ENERGY LEVELS so are FURTHER AWAY from the nucleus and experience LESS ATTRACTION to the nucleus due to their distance from the protons and because the other e- in inner shells act to SHIELD the valence e- from the nucleus
What is electronegativity?
a measure of the ability of an atom in a compound to attract e- to itself, particularly e- shared in a covalent bond
What is the first ionisation energy?
The energy required to remove the most loosely held valence electrons to convert one mole of gaseous atoms into one mole of gaseous ions, each with a charge of 1+
F.I.E decreases….
down a group
Explanation for decrease in F.I.E
down a group, valence e- are being added to SUCCESSIVE HIGHER ENERGY LEVELS
- each successive energy level is FURTHER FROM THE NUCLEUS
- due to this increased distance, the electrostatic attraction between the protons and e- DECREASES, WIDENING THE RADIUS
- inner e- shells also SHEILD THE NUCLEUS, and the attraction TOWARDS THE NUCLEUS IS DECREASED
- therefore ionisation energy is DECREASED
Explanation for increase in F.I.E
- across a period, successive valence e- are being added to the SAME ENERGY LEVEL while the number of protons is STEADILY INCREASING
- individual valence electrons experience attraction to the increasing number of protons
- this GREATER ATTRACTION towards the nucleus means MORE ENERGY is needed to remove the outermost electron and the ionisation energy is INCREASED
Ionisation energy of noble gases is high/low?
Ionisation energy of metal is high/low?
Ionisation energy of non metals gases is high/low?
- High because of the stability of the full e- levels
- Low which reflects how readily metals form cations
- High
Electronegativity increases…
across a period
Explanation for electronegativity increasing
- across a period, successive valence e- are being added to the SAME ENERGY LEVEL while the number of protons is STEADILY INCREASING
- individual valence electrons experience attraction to the increasing number of protons
- therefore attraction between BONDING e- and NUCLEUS is INCREASED
Electronegativity of noble gases is high/low?
Electronegativity of metal is high/low?
Electronegativity of non metals gases is high/low?
- noble gases are not assigned electronegativity values as they do not form covalent bonds
- low because their nuclei do not exert a strong attractive force for electrons
- high(er) because the nuclei do exert a strong attractive force for electrons
order of electronegativity is…
Fluorine > Oxygen > Nitrogen, Chlorine > Other Elements
