periodicity

Question 1

what was the old model of the periodic table

Answer 1

• just over 60 elements
  -Mendeleev arranged them in increasing order of atomic mass
• he lined up elements with similar properties in a group
• Mendeleev swapped elements assuming atomic mass was incorrect if it didn’t match the group properties
• left gaps for elements that wernt discovered
• predicted properties of missing elements from group trends

Question 2

what is the modern version of period table

Answer 2

-2014-> 114 elements
- elements arranged in increasing order of atomic number
-atoms in groups have same number of electrons in outer shell
- periods give highest energy electron shell in an elements atom

Question 3

what are the different groups called

Answer 3

group:
1- alkali metals
2- alkaline earth metals
3-12- transition elements
15- pnictogens
16- chalcogens
17- halogens
18- noble gases

Question 4

what is the first ionisation energy

Answer 4

the energy required to remove one electron from each atom in one mole of gaseous atoms of an element to form one mole of gaseous 1+ ions

Question 5

how does atomic radius affect ionisation energy

Answer 5

• the greater the atomic radius the further the distance between nucleus and outer electrons
• less nuclear attraction
• less energy needed to ionise

Question 6

how does nuclear charge affect ionisation energy

Answer 6

more protons–> greater the attraction between nucleus and outer electrons–> more energy needed to ionise

Question 7

how does sheilding affect ionisation energy

Answer 7

• reduces attraction between nucleus and outer electrons

Question 8

what is the second ionisation energy

Answer 8

the energy required to remove one electron from each ion in one mole of gaseous 1+ ions in an element to form one mole of gaseous 2+ ions

Question 9

what is the trends in ionisation energy across a group

Answer 9

• ionisation energy decrease
• atomic radius increases
• sheilding increases
• nuclear attraction decreases

Question 10

what is the trend in ionisation energy across periods

Answer 10

• generally increases
• nuclear charge increases
• same sheilding
• nuclear attraction increases
• atomic radius decreases

Question 11

why is there a fall in the first ionisation energy from beryllium to boron

Answer 11

-2p sub shell in boron has higher energy than 2s subshell in beryllium
- 2p electron in boron easier to remove than 2s electron in beryllium
- first ionisation energy less for boron than beryllium

Question 12

why is there a fall in first ionisation energy from nitrogen to oxygen

Answer 12

in nitrogen and oxygen first ionisation energy is in 2p subshell
- in oxygen the paired electrons in one of the 2p orbitals repel each other making it easier to remove an electron in oxygen than nitrogen
- first ionisation energy of oxygen less than the first ionisation energy of nitrogen

Question 13

why is there a fall in ionisation energy from magnesium to aluminium

Answer 13

in aluminium the distance between nucleus and outer electron increases
- sheilding increases
- less energy required to remove 3p electron of aluminium than electron of magnesium
- drop in ionisation energy

Question 14

why is there a fall in ionisation energy from phosphorus to sulfur

Answer 14

• electron in sulfur being removed from a p orbital containing 2 electrons that repel each other lowering ionisation energy