C7 - Periodic table and energy Flashcards
Who was responsible for the periodic table
Dmitri Mendeleev
How did Mendeleev organise the periodic table?
-In order of increasing atomic mass
-Grouped according to similar physical and chemical properties
-Left gaps for undiscovered elements
-Switched tellurium and iodine
Why didn’t Mendeleev accept noble gasses were elements?
They did not react
How is the periodic table arranged now
-Increasing atomic number
-7 horizontal periods
-18 vertical groups
What are groups?
Vertical column on periodic table
Elements with similar chemical properties and same number of outer-shell electrons
What are periods?
Horizontal rows in periodic table
Show trend in (physical) properties across a period
What’s periodicity?
Repeating trend in properties of element across each period of the periodic table
Periodic trend in electron configuration in period 2 and 3
-Period 2: 2s sub-shell fills with 2e-, 2p sub-shell fills with 6e-
-Period 3: 3s sub-shell fills with 2e-, 3p sub-shell fills with 6e-
What are blocks
Correspond to highest energy subshell
S block
P block
D block
F block
How are blocks arranged
What does ionisation energy measure?
How easily an atom loses electrons to form positive ions
What’s first ionisation energy?
Energy required to remove one electron from each atom in one mole of gaseous atoms of an element of form one mole of gaseous 1+ ions
First ionisation formula of Na
Na (g) —> Na+ (g) + e-
What factors affect ionisation energy?
Atomic radius
Nuclear charge
Electron shielding
How does atomic radius affect ionisation energy?
Greater distance between nucleus and out electrons
Less nuclear attraction
How does nuclear charge affect ionisation energy?
More protons
Greater attraction between nucleus and outer electrons
How does electron shielding affect ionisation energy?
Electrons are negatively charged
Inner shell electrons repel outer shell electrons
Reduce attraction between nucleus and outer electrons
What is shielding?
Repulsion between electrons in different inner shells
Reduces net attractive forces between nucleus and outer shell electrons