7. Trends In The Periodic Table

Question 1

Atomic radius def.

Answer 1

The atomic radius of an atom is defined as half the distance between two nuclei of atoms of the same element that are joined together by a single covalent bond.

Question 2

Atomic radius increase and decrease

Answer 2

Decrease across a period

Increase down groups

Question 3

Exception to atomic radius

Answer 3

Noble gases; they don’t form covalent bonds

Question 4

2 reasons why atomic radius increases down groups

Answer 4

• new energy level

- screening effect of inner electrons

Question 5

2 reasons why atomic radius decreases across periods

Answer 5

• increase effective nuclear charge

- no increase in screening effect

Question 6

Increase in effective nuclear charge: atomic radius

Answer 6

• no. of protons increases
• increased pos. pull on outer electrons
• draws closer to nucleus

Question 7

No increase in screening effect

Answer 7

• extra electrons SAME energy level
• no new energy level to add to screening effect
• and shield outer electrons from pos.charge

Question 8

First ionization energy

Answer 8

First ionization energy of an atom is the minimum energy required to completely remove the most loosely bound electron from a neutral gaseous atom in its ground state.

Question 9

Formulas for ionization energies

Answer 9

X(g) —> X+(g) + e-

X+(g) —> X2+(g) + e-

X2+ (g) ——> X3+(g) + e-

Question 10

Second ionization energy

Answer 10

Second ionization energy is the energy required to remove an electron from an ion with one positive charge in the gaseous state.

Question 11

Ionization increase and decrease

Answer 11

Increase across periods

Decrease down groups

Question 12

2 reasons ionization increase across:

Answer 12

• Increase effective nuclear charge

- decreasing atomic radius

Question 13

Increase effective nuclear charge : ionization

Answer 13

-no.of protons increasing
-increased pos.attraction
-electrons held more firmly
I.e more energy required to remove them

Question 14

Decreasing atomic radius : ionization

Answer 14

-outermost electrons getting closer
-increased attraction between nucleus and electron
,, more energy required for removal

Question 15

Increase screening effect : ionization decrease

Answer 15

-although nuclear charge increases, pos.force canceled out by corresponding screening effect
-outermost electrons shielded from pos pull.
,, easier, less energy to remove

Question 16

Why is there exceptions to ionization trend?

Answer 16

Any sublevel that is completely filled or half filled has extra stability.
More energy required to break into these stable levels- jump in graph.

Question 17

4 exceptions to ionization

Answer 17

Be, N, Mg, P

bean magpie ;

Question 18

Evidence for energy levels from ionization

Answer 18

• second e always harder to remove as it’s taken from a K+ ion
• sudden large jumps imply we’re breaking into a new energy level w extra stability, closer to nucleus

Question 19

2 reasons why ionization values increase

Answer 19

-Pos. Charge on ions increases for each e removed : greater pos. Attraction on remaining electrons
- pos ions becoming smaller as e removed.
e closer to nucleus; increased attraction.

Question 20

Electronegativity increase &decrease

Answer 20

Same as ionization.
Increase across,
Decrease down.

Question 21

2 reasons electronegativity increase across

Answer 21

• increase effective nuclear charge

- decreasing atomic radius

Question 22

Increase effective nuclear charge: electronegativity increase

Answer 22

• no.of protons increase

- greater pos.attraction on outermost electrons involved in bonding

Question 23

2 reasons for electronegativity decrease

Answer 23

1. Increase atomic radius

2. Increase screening effect

Question 24

Alkali metals what sort of compounds & why

Answer 24

Ionic compounds

• low ionization energy
• low electronegativity

Question 25

reason alkali reactivity increases down group

Answer 25

- atomic radius increases - screening effect too - causes ioniz.energy to decrease - outermost electrons more easily lost

Question 26

Alkali metals oxygen reaction notes

Answer 26

- form oxides - stored under oil - lose shiny colour when exposed to air

Question 27

Alkali metals oxygen reaction formula

Answer 27

2K + 1/2 O2 —-> K2O

Question 28

Alkali metal + water.what do they form

Answer 28

Hydroxide +hydrogen gas

Question 29

Alkali metal + water formula

Answer 29

Na +H2O —-> NaOH + 1/2H2

Question 30

Halogens notes

Answer 30

- very reactive: need 1 electron - oxidizing agents (take electrons) - not free in nature - most electronegative

Question 31

Halogens reactivity increas/decrees

Answer 31

Increases UP the group

Question 32

Reason halogen reactivity increase up the group

Answer 32

- most electronegative @top - bc electronegativity decreases down - greater pull on electrons - easier to react to draw in other e & fill outer level

Question 33

Halogens experiment

Answer 33

Cl (g) bubbled through bromide ions solution - cl takes e ; more electronegative - turns bromide into bromine - colorless solution turns red

Question 34

Halogens experiment formula

Answer 34

Cl2 + 2Br- —-> 2Cl- + Br2

Question 35

The same can be seen as in the experiment w halogens in..

Answer 35

Bromine + iodide ions —-> iodine

Question 36

Sentence summing up halogen experiment

Answer 36

The more reactive halogen displaced the less reactive halogen from a solution of its ions.

Question 37

Boilin points halogens : increase or decrease

Answer 37

Increase down the group

Question 38

Reason why boiling point increases down group of halogens

Answer 38

- atomic radius increases - electron clouds bigger - greater chance to form temporary dipoles - stronger van der Waals forces

Question 39

Examples of halogens showing the boiling point :

Answer 39

Fl, Cl: gas Br: liquid Iodine : solid. At room temp