Periodicity Flashcards
periodicity
repeated patterns in periodic table
period
row across periodic table
group
column down periodic table
In what order are elements on periodic table arranged?
atomic number
What do elements in the same period have?
outer electrons in same shell
What do elements in the same group have?
same number of outer electrons
As the number of protons increases…
attractions of electrons to nucleus increases
As the number of full shells increases…
- repulsion is greater
- electrons pulled less strongly towards nucleus
Trend in atomic radius across period
- same number of shells
- more protons electrons
- pulled more strongly toward nucleus
- radius decreases across period
Trend in atomic radius down group
- more protons
- number of shells increases
- electrons repelled more
- less attraction to nucleus
- atomic radius increases down group
Trend in ionic radius across period
- metallic ions lose electrons so have one fewer shell so size decreases non-metal
- ions gain electrons so have one more shell so size increases
Trend in ionic radius down group
- protons increases
- shells increase
- ionic size increases because electrons held less tightly
Trend in electronegativity across period
- more protons
- same number of shells
- greater attraction to nucleus
Trend in electronegativity down group
- more protons
- more shells
- less attraction of electrons to nucleus
electronegativity
ability to attract a pair of electrons towards self in covalent bond
halogens
reactive group of non-metals in group 17
noble gases
very unreactive family of non-metals found at extreme right-hand side in group 18
alkali metals
reactive group of metals in group 1
lanthanoides and actinoides
metals which make up first and second row of f block
metalloid elements
have characteristics of both metals and non-metals
trend in ionization energy across period
- increases
- effective nuclear charge increases
- increase in attraction between outer electrons and nucleus
- more difficult to remove electrons
trend in ionization energy down group
- decreases
- electron is removed from energy level furthest from nucleus
- nuclear charge increases
- effective nuclear charge about the same (shielding of inner electrons)
- increased distance between electron and nucleus reduces attraction
What accounts for the drop in IE between group 15 and 16?
- electron removed from group 16 element comes from doubly occupied p orbital
- easier to remove as it is repelled by partner
Why do elements with valence electron in p orbitals have lower IE?
p orbitals have higher energy than s orbitals
electron affinity
energy change when one mole of electrons is added to one mole of gaseous atoms to form one mole of gaseous ions
What is the equation for electron affinity of element X?
X(g) + e- –> X-(g)
Why do noble gases have no electron affinities?
generally do not form negative ions
What is the second electron affinity for oxygen?
O- + e- –> O2-
Is second electron affinity endothermic or exothermic? Why?
endothermic added electron is repelled by negatively charged ion energy needs to be available therefore for this to occur
What is the EA for group 17?
- incomplete outer energy levels
- high effective nuclear charge
- attract electrons the most
What is the EA for group 1?
- lowest effective nuclear charge
- attract electron the least
What is the EA for group 2 and 3?
- maximum EA
- electron must be placed in p orbital further from nucleus
- experiences reduced electrostatic attraction due to shielding
What is the EA for group 15?
- added electron must occupy singly occupied p orbital
- increased inter-electron attraction
- attraction between electron and atom less
