Topic 3: periodicity

Question 1

what are group 1 elements called?

Answer 1

alkali metals

Question 2

what are group 2 elements called?

Answer 2

alkali earth metals

Question 3

what are group 18 elements called?

Answer 3

noble gases

Question 4

what are group 17 elements called?

Answer 4

halogens

Question 5

what is the trend in atomic radius?

Answer 5

• Period: decreases
• Group: increases

Question 6

why does atomic radius decrease across a period?

Answer 6

• no. of protons increases
• no. of electron shells stay the same
• stronger attraction between nucleus and valence electrons

Question 7

why does atomic radius increases down a group?

Answer 7

no. of occupied electron shells increases

Question 8

what is the trend in ionic radius?

Answer 8

• cations: decreases
• anions: increases

Question 9

why does ionic radius increase for anions?

Answer 9

added electrons cause more repulsion between valence electrons

Question 10

why does ionic radius decrease for cations?

Answer 10

no. of occupied electron shells decreases

Question 10

Why does first ionisation energy decrease down a group?

Answer 10

the removed electron is from an electron shell further away from the nucleus.

Question 11

what are the trends in first ionisation energy?

Answer 11

• period: increases
• group: decreases

Question 12

what is the definition of first ionisation energy?

Answer 12

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

Question 13

what is electron affinity?

Answer 13

the energy released when an electron is added to a gaseous atom.

Question 14

write the equation to the first electron affinity

Answer 14

X (g) + e⁻ → X⁻ (g)

Question 15

what are the trends in electron affinity?

Answer 15

• Period: increases
• group: decreases

Question 16

the second electron affinity is _______________(exothermic/endothermic)

Answer 16

endothermic

Question 17

why is the second electron affinity an endothermic process?

Answer 17

you’re adding a negatively charged electron to an already negative ion. Since like charges repel, overcoming this repulsion requires energy.

Question 18

what is electronegativity?

Answer 18

the attraction an atom has for the shared pair of electrons in a covalent bond.

Question 19

what are the trends in electronegativity?

Answer 19

• Period: increases
• group: decreases

Question 20

why does electronegativity increase across a period?

Answer 20

• smaller atomic radius
• bonding electrons are held more tightly to nucleus

Question 21

why does electronegativity decrease down a group?

Answer 21

• larger atomic radius
• bonding electrons are held less tightly to nucleus

Question 22

What are transition metals?

Answer 22

elements that have incomplete d-orbitals

Question 23

What is an exception in transition metals?

Answer 23

Zinc

Question 24

what are the physical properties of transition metals?

Answer 24

* high electrical/thermal conductivity * high melting points * malleable + ductile * high tensile strength * has magnetic properties

Question 25

What are the chemical properties of transition metals?

Answer 25

* have more than one oxidation states in compounds * form complex ions * form coloured compounds in solution * can act as catalysts

Question 26

What is the relationship between the strength of magnetism and the number of unpaired electrons ?

Answer 26

magnetism increases as the number of unpaired electrons increases

Question 27

What is diamagnetism?

Answer 27

* no unpaired d-electrons * weakly repelled by an external magnetic field

Question 28

what is paramagnetism?

Answer 28

* one or more unpaired d-electrons * attracted by an external magnetic field * paramagnetism increases with increasing number of unpaired electrons.

Question 29

What gasses cause acid rain?

Answer 29

* SO3 * SO2 * NO2

Question 30

what types of oxides form basic solutions when reacted in water?

Answer 30

metallic oxides

Question 31

what are two metallic oxides?

Answer 31

* Na2O * MgO

Question 32

What type of oxide forms amphoteric solutions when reacted with water?

Answer 32

metalloid oxides

Question 33

What type of oxide forms acidic solutions when reacted with water?

Answer 33

non-metal oxides

Question 34

What is one metalloid oxide?

Answer 34

Al₂O₃