S3.1 Periodic table

Question 1

what is periodicity?

Answer 1

repeating pattern of physical and chemical properties because of specific periodic trends

Question 2

what is nuclear charge?

Answer 2

cumulative total positive charge in the nucleus-linked to no. of protons present

Question 3

how does nuclear charge change across a period and down a group?

Answer 3

increases across a period and decreases down a group

Question 4

how does shielding change across a period and down a group?

Answer 4

stays the same across a period but increases down a group

Question 5

how does atomic radius change across and period and down a group?

Answer 5

increases down a group bc electrons are added further from the nucleus; decreases across a period bc of the increase in nuclear charge and no change in shielding so electrostatic attraction increases and electrons pulled inwards

Question 6

how does ionic radius change across a period and down a group?

Answer 6

increases down a group bc atomic radius increases; decreases across a period bc increased nuclear charge w same no. of electrons within the ion so electrostatic attraction increases

Question 7

what is electronegativity?

Answer 7

the ability of an atom to pull electrons in a covalent bond

Question 8

how does electronegativity change across a period and down a group?

Answer 8

decreases down a group bc of increased shielding that outweighs the increase in nuclear charge so electrostatic attraction decreases; increases across a period bc increased nuclear charge and no change in shielding so electrostatic attraction increases

Question 9

what is ionisation energy?

Answer 9

energy required to remove one mole of electrons from one mole of gaseous atoms

Question 10

how does ionisation energy change across a period and down a group?

Answer 10

decreases down a group bc increased shielding that outweighs the increase in nuclear charge so electrostatic attraction decreases and takes less energy to remove an electron; increases across a period bc increased nuclear charge and no change in shielding so electrostatic attraction increases and takes more energy to remove an electron

Question 11

what is electron affinity?

Answer 11

energy(enthalpy) change when one electron is added to a gaseous atom

Question 12

how does electron affinity change across a period and down a group?

Answer 12

decreases down a group bc increased shielding that outweighs the increased nuclear charge so electrostatic attraction decreases(except fluorine); increases across a period bc of increased nuclear charge and no change in shielding so electrostatic attraction increases(except phosphorus)

Question 13

what is the first electron affinity and why?

Answer 13

negative so exothermic because atoms generally want to gain electrons so this reaction is favourable

Question 14

what is the 2nd electron affinity and why?

Answer 14

usually positive bc the negative ion created from the 1st electron affinity repels any additional electrons so reaction is less favourable

Question 15

alkali metals

Answer 15

soft v reactive; down group reactivity increases and mp decreases; low mp and bp; react with O2 and H2O

Question 16

alkali+oxygen

Answer 16

metal oxide; usually stored in liquid paraffin to avoid air

Question 17

alkali+H2O

Answer 17

metal hydroxide+hydrogen gas; hydroxide can dissolve to form an alkaline solution

Question 18

how do lithium, sodium and potassium react with water?

Answer 18

lithium reacts quietly and floats on surface; sodium reacts more vigorously and floats on surface as a sphere; potassium reacts even vigorously and moves on surface burning w lilac flame

Question 19

how do halogens react with alkali metals?

Answer 19

form white or colourless neutral salts which are soluble in water

Question 20

how do halogens react with halide solutions?

Answer 20

the more reactive halogen displaces the less reactive halogen

Question 21

how can you test for the presence of halide ions?

Answer 21

through the addition of silver nitrate solution

Question 22

what will form if chloride ions are present?

Answer 22

white precipitate

Question 23

what will form if bromide ions are present?

Answer 23

cream precipitate

Question 24

what will form if iodide ions are present?

Answer 24

yellow precipitate

Question 25

what is isoelectronic?

Answer 25

when different ions contain the same number of electrons

Question 26

how and why does the m.p. change going down group 1?

Answer 26

m.p. decreases going down because atoms become larger and strength of metallic bond decreases

Question 27

how and why does the m.p. of group 17 change going down?

Answer 27

attractive forces between the diatomic molecules increase down the group so the m.p. increase

Question 28

why are alkali metals good reducing agents?

Answer 28

because they can readily lose an electron

Question 29

why are alkali metals called that?

Answer 29

because they all react with water to form an alkaline solution of the metal hydroxide and hydrogen gas

Question 30

halogens are…

Answer 30

good oxidising agents-this is why displacement reactions take place

Question 31

draw p3 oxide table

Question 32

what is the trend of electron affinity down a group?

Answer 32

decreases and values become less exothermic

Question 33

what is an oxidising agent?

Answer 33

a species that oxidises another species by taking electrons from it

Question 34

what is a reducing agent?

Answer 34

species that reduces another species by giving electrons to it

Question 35

general equation for group 1 oxide reacting with water

Answer 35

M2O(s)+H2O(l)—>2MOH(aq)

Question 36

general equation for a group 2 oxide reacting with water

Answer 36

MO(s)+H2O(l)—>M(OH)2(aq)

Question 37

what is ocean acidification?

Answer 37

the reduction of the pH of the oceans over an extended period of time through the increased uptake of CO2 from the atmosphere

Question 38

what is acid rain?

Answer 38

rain with a pH lower than 5.6