The Periodic Table

Question 1

how is the periodic table arranged?

Answer 1

• group no. = no. electrons in outermost energy level
• period no. = no. occupied energy levels
• in order of increasing atomic no.

Question 2

what determines chemical properties and physical properties of an element?

Answer 2

no. electrons determines chemical properties.

atomic mass determines physical properties.

Question 3

explain the trend in atomic radii across a period:

Answer 3

bc nuclear charge increases but electron shielding remains constant, attraction betw. valence electrons and nucleus increases, so atomic radii decreases

Question 4

trend in atomic radii down a group:

Answer 4

atomic radii increases down a group bc no. occupied energy levels increase

Question 5

how does atomic radii differ to ionic radii?

Answer 5

-+ve ions = smaller than parent atoms bc formation of
+ve ions = loss of outer energy level
-negative ions larger than parent atoms bc formation of -ve ions = addition of electrons= greater repulsion betw. electrons

Question 6

define first electron affinity

Answer 6

energy change that occurs when 1 mole electrons is added to a mole of gaseous atoms

Question 7

how does ionic radii change down a group?

Answer 7

increases down a group bc additional no. occupied energy levels

Question 8

how does ionic radii change across a period?

Answer 8

• -ionic radii, decreases from groups 1,2,13,14 for +ve ions bc nuclear charge increases while electron no. remains the same= greater attraction betw. outer electrons and nucleus
• -ionic radii decreases from groups 14-17 for -ve ions bc nuclear charge increases whilst electron no. remains the same= greater attraction

Question 9

trend in first electron affinity across a period:

Answer 9

electron affinities become more exothermic along a period bc effective nuclear charge increases so attraction betw. +ve nucleus and valence electrons increases = stronger attraction and -ve energy change

Question 10

trend in first electron affinity down a group:

Answer 10

becomes less exothermic down a group, bc more electron shielding= less attraction betw. + nucleus and valence electrons= weaker attraction and less negative energy change

Question 11

define electronegativity:

Answer 11

ability of an atom to attract a shared pair of electrons in a covalent bond

Question 12

explain trends in electronegativity along a period:

Answer 12

increases from left to right bc greater effective nuclear charge and same no. occupied shells = smaller atomic radii= greater attraction to electrons

Question 13

trends in electronegativity down a group:

Answer 13

electronegativity decreases down a group bc more occupied shells = more electron repulsion, more electron shielding and atomic radii increases so reduced attraction betw. nucleus and shared pair

Question 14

define metallic character

Answer 14

ease w/ which valence electrons = lost and +ve ions formed

Question 15

how metallic character changes down a group:

Answer 15

increases down a group bc increase in effective nuclear charge = greater strength of attraction betw. nucleus and valence electrons

Question 16

how metallic character changes across a period

Answer 16

decreases across a period bc increase in effective nuclear charge= greater attraction betw nucleus and valence electrons

Question 17

how melting points change down group 1:

Answer 17

decrease down group 1 bc electrostatic attraction betw. delocalised valence electrons and +ve ions = lower bc increase in distance and more electron shielding

Question 18

how melting points change down group 17:

Answer 18

increase down group 17 bc group 17 elements have simple molecular structures and London dispersion forces increase as no. electrons and molar mass increase

Question 19

how do group 1 metals react w/ oxygen and water?

Answer 19

• react vigorously w/ water to form metal hydroxide + hydrogen
• react vigorously w/ oxygen to form basic oxides

Question 20

explain why fluorine= more reactive than chlorine:

Answer 20

fluorine has 2 occupied energy shells, chlorine has 3. chlorine has greater atomic radius and electron shielding, meaning less attraction to electrons to fill valence shell.
-for chlorine, valence electrons= closer to nucleus w/ stronger electrostatic attraction so easier for fluorine to gain electron

Question 21

define first ionisation energy

Answer 21

energy required to remove outermost electron from a gaseous atom

Question 22

how does first ionisation energy change down a group?

Answer 22

first ionisation energy decreases bc greater electron shielding and higher atomic radius means electron= less strongly attracted to nucleus

Question 23

how does first ionisation energy change along a period?

Answer 23

first ionisation energy increases along a period bc